Assessment of extent of variability induced by gamma rays ...prr.hec.gov.pk/jspui/bitstream/123456789/7825/1... · 2 DECLARATION I hereby declare that the contents of the thesis “Assessment

1

Assessment of extent of variability induced by gamma rays in maize

(Zea mays L.)

By

Qamar u Zaman

2008-ag-2390

B.Sc. (Hons.) Agri.

A thesis submitted in partial fulfilment of the requirements for the degree of

MASTER OF SCIENCE (HONOURS)

i n

Plant Breeding and Genetics

DEPARTMENT OF PLANT BREEDING AND GENETICS

FACULTY OF AGRICULTURE

UNIVERSITY OF AGRICULTURE FAISALABAD,

PAKISTAN

2015

2

DECLARATION

I hereby declare that the contents of the thesis “Assessment of extent of variability induced by

gamma rays in maize (Zea mays L.)” are product of my own research and no part has been copied

from any published source (except the references, standard mathematical or genetic

models/equations/formulae/protocols etc). I further declare that this work has not been submitted for

award of any diploma/degree. The university may take action if the information provided is found

inaccurate at any stage (In case of any default the scholar will be proceeded against as per HEC

plagiarism policy.

Qamar u Zaman

Regd. No. 2008-ag-2390

To,

The Controller of Examinations,

3

University of Agriculture,

Faisalabad.

We, the supervisory committee certify that the contents and form of thesis submitted by

Qamar u Zaman. Regd. No.2008-ag-2390 have been found satisfactory and recommend that

it be processed for evaluation by the external examiner(s) for the award of the degree.

SUPERVISORY COMMITTEE

Chairman _____________________________

Dr. Muhammad Aslam

Member _____________________________

Dr. Muhammad Ahsan

Member _____________________________

Dr. Muhammad Shahbaz

4

Dedicated To

My Parents

ACKNOWLEDGMENTS

All the gratitude to ALLAH ALMIGHTY, the compassionate and Merciful, who

enable me to elucidate a drop from the existing ocean of knowledge. All praises to the HOLY

PROPHET MUHAMMAD ( ); the city of knowledge, the illuminating torch whose

teaching enlightened my heart and flourished my thoughts.

I have no appropriate words to express my heartiest thanks to my honorable

supervisor, Dr. Muhammad Aslam, Assistant Professor, Department of Plant Breeding and

Genetics, University of Agriculture, Faisalabad, who acted as a real spiritual teacher and

provided his dexterous guidance and valuable suggestion throughout my research effort and

write-up of thesis. I am grateful to my respectable supervisory committee Dr. Muhammad

5

Ahsan, Associate Professor, department of Plant Breeding and Genetics, University of

Agriculture, Faisalabad and Dr. Muhammad Shahbaz, Assistant Professor, department of

botany, University of Agriculture Faisalabad, for their keen interest, encouragement and

valuable suggestion during research work.

.

Qamar u Zaman

CONTENTS

CHAPTER TITLE PAGE

01 INTRODUCTION 01

02 REVIEW OF LITERATURE 03

03 MATERIALS AND METHODS 10

04 RESULTS AND DISCUSSION 13

05 SUMMARY 132

LITERATURE CITED 134

6

LIST OF TABLES

Table

No. Title Page #

4.1.1.1 Summary statistics for final height of maize under

different treatments 15

4.1.1.2 Frequency distribution for final plant height without

irradiation (Control)

16

4.1.1.3 Frequency distribution for final plant height at 20

Gray (Gamma Radiation)

17


Gray (Gamma Radiation) 19



4.1.1.6 Frequency distribution for the final plant height at

80 Gray (Gamma Radiation) 21

4.1.2.1 Summary statistics for days to silking of maize

under different treatments 26

4.1.2.2 Frequency distribution for days to silking without

irradiation c(Control) 27

4.1.2.3 Frequency distribution for days to silking at 20 Gray

(Gamma Radiation) 28







7

4.1.3.1 Summary statistics for days to tasseling of maize under

different treatments 34

4.1.3.2 Frequency distribution for days to tasseling without

irradiation (Control) 35

4.1.3.3 Frequency distribution for days to tasseling at 20 Gray







(Gamma Radiation)

37

4.1.4.1 Summary statistics for number of grain rows per cob of

maize under different treatments

42

4.1.4.2 Frequency distribution for number of grain rows per

cob without irradiation (Control)

43


cob at 20 Gray (Gamma Radiation)

43



44



45



45

4.1.5.1 Summary statistics for cobs length of maize under

different treatments

50

4.1.5.2 Frequency distribution for cobs length without


51

8

4.1.5.3 Frequency distribution for cobs length at 20 Gray

(Gamma Radiation)

52


(Gamma Radiation)

53


(Gamma Radiation)

54


(Gamma Radiation).

54

4.1.6.1 Summary statistics for number of cobs per plant of

maize under different treatments

59

4.1.6.2 Frequency distribution for number of cobs per plant

without irradiation (Control).

60

4.1.6.3 Frequency distribution for number of cobs per plant at 20 Gray

(Gamma Radiation)

60


(Gamma Radiation)

61

4.1.6.5 Frequency distribution for number of cobs per plant at

60 Gray (Gamma Radiation)

61


(Gamma Radiation)

62

4.1.7.1 Summary statistics for diameter of cobs under

different treatments

66

4.1.7.2 Frequency distribution for diameter of cob without


67

4.1.7.3 Frequency distribution for diameter of cob at 20 Gray

(Gamma Radiation)

68

4.1.7.4 Frequency distribution for diameter of cob at 40 Gray

(Gamma Radiation)

69

9

4.1.7.5 Frequency distribution for diameter of cob at 60


70

4.1.7.6 Frequency distribution for diameter of cobs at 80


4.1.8.1 Summary statistics for number of grains per row of

maize under different treatments 77

4.1.8.2 Frequency distribution for number of grains per

row with irradiation (Control) 77


row at 20 Gray (Gamma Radiation) 79







4.1.9.1 Summary statistics for number of grains per cob of



cob without irradiation (Control) 88


cob at 20 Gray (Gamma Radiation) 90







10

4.1.10.1 Summary statistics for grains weight per cob of


4.1.10.2 Frequency distribution for grains weight per cob

without irradiation (Control) 101


at 20 Gray (Gamma Radiation) 102







4.1.11.1 Summary statistics for 100 grains weight of


4.1.11.2 Frequency distribution for 100 grains weight at

normal without irradiation (Control) 113






60 Gray (Gamma Radiation). 117



4.1.12.1 Summary statistics for yield per plant of maize

under different treatments 122

4.1.12.2 Frequency distribution for grains yield per plant

without irradiation (Control) 122



11







12

LIST OF FIGURES

Figure

No. Title Page #

4.1.1.1 Histogram for final plant height at non-irradiation

condition (Control) 22

4.1.1.2 Histogram for final plant height at 20 Gray








4.1.2.1 Histogram for days to silking at non-irradiation

condition (Control) 30

4.1.2.2 Histogram for days to silking at 20 Gray (Gamma

Radiation) 30

4.1.2.3

Histogram for days to silking at 40 Gray (Gamma

Radiation)

31


Radiation) 31


Radiation) 32

4.1.3.1 Histogram for days to tasseling at non-irradiation

condtion (Control) 38

4.1.3.2 Histogram for days to tasseling at 20 Gray (Gamma

Radiation) 38


Radiation) 39

13


Radiation) 39


Radiation) 40

4.1.4.1 Histogram for number of grain rows per cob at nonirradiation

condition (Control)

46

4.1.4.2 Histogram for number of grain rows per cob at 20


46



47



47



48

4.1.5.1 Histogram for cobs length at non-irradiation condition

(Control)

55

4.1.5.2 Histogram for cobs length at 20 Gray (Gamma

Radiation)

56


Radiation)

56


Radiation)

57


Radiation)

57

4.1.6.1 Histogram for number of cobs per plant at non-

irradiation condition (Control)

62

4.1.6.2 Histogram for number of cobs per plant at 20 Gray

(Gamma Radiation)

63

14


(Gamma Radiation)

63


(Gamma Radiation)

64


(Gamma Radiation)

64

4.1.7.1 Histogram for diameter of cobs at non-irradiation

condition (Control)

72

4.1.7.2 Histogram for diameter of cobs at 20 Gray (Gamma

Radiation)

73


Radiation)

73


Radiation)

74


Radiation)

74

4.1.8.1 Histogram for number of grains per row at non-

irradiation condition (Control)

83

4.1.8.2 Histogram for number of grains per row at 20 Gray


4.1.8.3

Histogram for number of grains per row at 40 Gray

(Gamma Radiation)

84


(Gamma Radiation)

84


(Gamma Radiation)

85

4.1.9.1 Histogram for number of grains per cob at non-

irradiation condition (Control) 96

15

4.1.9.2 Histogram for number of grains per cob at 20 Gray

(Gamma Radiation)

96


(Gamma Radiation)

97





4.1.10.1 Histogram for grains weight per cob at non-


4.1.10.2 Histogram for grains weight per cob at 20 Gray








4.1.11.1 Histogram for 100 grains weight at non-irradiation

condition (Control)

118

4.1.11.2

Histogram for 100 grains weight at 20 Gray

(Gamma Radiation)

119

4.1.11.3 Histogram for 100 grains weight at 40 Gray






16

4.1.12.1 Histogram for grains yield per plant at non-


4.1.12.2 Histogram for grains yield/plant at 20 Gray


4.1.12.3 Histogram for grains yield per plant at 40 Gray





(Gamma Radiation)

131

17

Abstract

Gamma rays were used to induce mutation in maize variety (Sultan) with four irradiation

doses (20 Gray, 40 Gray, 60 Gray and 80 Gray) and compared with non-irradiated set. Data

were collected for morphological traits like Plant height (cm), number of days to silking,

number of days to tasselling, number of grain rows per cob, cob length (cm), number of cobs

per plant, diameter of the cob, number of grains per row, number of grains per cob, grain

weight per cob, 100 grain weight and for grain yield per plant. Frequency distribution and

histogram were used to find effects of different irradiation doses on individual plants. Under

different Irradiation doses positive and negative effects were observed in studied genotype.

Plant height, cob length, grains weight per cob and 100 grains weight were increased at dose

of 20 gray as compared to non-irradiation conditions (normal). Number of grain rows per cob

and number of cobs per plant increased at the dose of 40 gray as compared to the non-

irradiated set. Days taken to silking reduced to 57 days from 62 days and days taken to

tasseling showed early development in 53 days at the dose of 60 gray which showed positive

mutation. Fertility in maize, diameter of cob, number of grains per row, number of grains per

cob were negatively affected by radiation treatments. Decreasing trend was observed in yield

per plant; yield decreased up to 86 g (60 gray) as compared to 194g at non-irradiation

condition. At the dose of 80 gray, 100 grain weight increased as compared to non-irradiation

treatment. Summary statistics showed that mutations in polygenic traits were random and did

not follow any particular pattern in all mutagenic doses.

18

Chapter 1 Introduction

Maize is one of the most important cereal crops in the world. It is a staple food for

200 million people in developing countries of the world from morning till noon (Tagne et

al, 2008). In developed countries; maize is used as a second-cycle product, in the form of

meat, eggs and dairy products (Rensburg, 2012). The grains of maize contain vitamins A,

C and E, carbohydrates, essential minerals, and 9% protein (Anonymous 4) in addition to

fuel and starch in processed form. During enzymatic process, starch converts into sorbitol,

dextrin, sorbic and lactic acid. These starch products are used in beer, ice cream, syrup,

shoe polish, glue, fireworks, ink, batteries, mustard, cosmetics, aspirin and paint.

Around 60% of world maize is used for animal feed. That‟s why maize importance is

increasing day by day indirectly due to the increasing demand of meat; it is necessary to

raise more number of animal heads to meet human requirement of meat (Anonymous 1).

This means that the global importance of maize is expanding where growth in meat

consumption is increasing (Jatta, S., 2013). It is also necessary to develop the maize

hybrids, inbred lines and varieties to feed the population of the world which is projected to

reach 9.6 billion by 2050 (Anonymous 2).

As illustrated above, there is a dire need to grow, cultivate and to develop maize

varieties, inbred lines and hybrids to meet the demand of geometrically increasing

population of the world which use the maize crop directly and indirectly to live in this world

successfully. And in this regard, only variation plays important role to develop varieties,

inbred lines and hybrids. To create variation in the existing varieties of the concerned crop;

natural and induced mutations play a key role to bring diversity in plant species.

For the induction of mutation; there are several mutagens but three approaches are

mostly used such as physical, chemical and transposon insertions. Mutant are the basic units

to create mutation in plant research fields i.e. plant physiology, genetics and plant breeding.

Physical mutagens are alpha rays, beta rays, fast neutrons, electromagnetic radiations, X-

rays and gamma rays and chemical mutagens (ethyl methane sulphonate, methyl methane

sulphonate, acridine dye etc.). Biological mutagens are also used to generate mutation such

as T-DNA insertion and transposons tagging. In China, spacecraft, recovery satellites, and

high altitude balloons are used to bring seeds in space to create mutation induction (Shu,

2009). Mutation can also be created by using restriction endonucleases which are helpful

for inducing double strand breaks in the plant genome. This technology further integrated

19

with the zinc finger DNA binding proteins (zinc finger nucleases) and it is also used for

site-specific mutagenesis (Belhaj, 2013).

Man‟s successful attempt to reproduce and scaling up the occurrence of natural

phenomenon through induced mutation are fruitfully exploited (Mba, 2013). Through

induced mutation, one can exploit polygenic and monogenic traits of any crop for the

improvement of existing germplasm. Developing embryo is suitable to study and to

evaluate the comparative analysis of genetic effects which are caused by the gamma rays

and chemical mutants. Comparison of these effects may helpful in determining linkage

between endosperm and other seedling markers to point out exact genetic changes

(Chatterjee et al., 1965).

Physical mutagens are high energy alpha (α) and beta (β) particles and neutrons.

These physical agents are used to break the chemical bonds, deletion, duplication,

inversion, translocation or addition of nucleotides. These agents can also be used to

substitute one nucleotide by another nucleotide. Mutants can also be engaged to break and

in rearrangement of chromosomes (Ahloowalia et al., 2001).

Gamma rays emitted by physical mutagens during the decaying process of

radioisotopes like cobalt-60 (60Co), cesium-137 (137Cs) to a lesser extent plutonium-239

(239Pu) and these mutants are helpful as a raw material for crop improvement (Mba, 2013).

These mutants create mutation on the reproductive and somatic cells of the plant or any

other exposed surface of the living object. The mutation is the only subject which

contributes to the evolution, it can be passed from one generation to another generation, if

it is germ line mutation.

Mutations mostly have negative effects, if active site of the amino acid is altered, it

may decrease or destroy the function of protein. But small percentage of mutation actually

improves the function of gene and gene product which provides the “grist” for the

evolutionary mill (Anonymous 3). Evolution absolutely depends on mutations because

mutation is the only way to create new alleles and new regulatory regions (Anonymous 5).

Chapter 2 Review of Literature

Pooler and Scorza (1997) studied the effect of gamma irradiation treatment in

combination with on ultraviolet germination percentage and fertility of pollen of peach

plant. Different levels of gamma irradiations were applied varying from 290 to 9000 Gray

20

on pollens with heat treatment of 100 degree for 2 hours. Pollens were used to pollinate

large number of male sterile plants. In vitro conditions, germination effect showed that

germination percentage was effected by all levels of gamma irradiation treatments while

low level doses were still able to maintain germination capacity. It was concluded that these

results were useful in production of hybrid and maternally derived haploids for successful

breeding programs.

Debnath and Khan (1991) observed that in maize plant height, days to silking and

grain weight had contributed positively to grain yield.

Jadhav et al (1991) studied the strength of association of traits in maize and found

positive association between plant height and numbers of ear per plant with grain yield.

Tahir (1991) investigated that plant height was significantly correlated with grain yield at

different genotypic levels of maize. Number of days taken to silking and number of days

taken to tasseling was non significantly and positively correlated with grain yield. Path

coefficient analysis depicted that ear diameter showed maximum direct effects while ear

length showed maximum indirect negative effect. Plant height and number of ears per plant

had positive effects on grain yield. Number of kernels per row showed negative while grain

weight showed small direct negative effects on grain yield.

Saha and Mukherjee (1993) performed an experiment on maize hybrid and observed that

ear diameter and number of kernel rows had positive and higher direct and indirect effects

on grain yield.

Mahajan et al. (1995) performed an experiment on eight different inbred lines of maize

following half diallel fashion resulting 28 hybrids in two different seasons. They examined

that grain yield was significantly associated with ear length while other yield contributing

traits had significant direct and indirect effects to grain yield.

Aziz et al. (1998) conducted an experiment on maize and observed that plant height and

number of kernel rows per plant had significant and positive effects on grain yield. Positive

but non-significant relation was noticed between ear diameter and grain yield. Negative

correlation was observed between ear length, ear diameter and number of kernel rows per

ear with grain yield.

21

Manivannan (1998) investigated direct and indirect effects of different yield related traits

on grain yield of maize hybrids. He concluded that ear diameter; ear length and grain weight

had positive significant effects on grain yield while kernel rows and seed weight had

positive direct effects.

Firoz et al. (1999) reported that grain yield per plant was significantly associated with yield

related traits of maize plants. Path coefficient analysis revealed that number of kernels per

ear and grain weight were mandatory components for calculating grain yield.

Gautam et al. (1999) evaluated correlation and path coefficient analysis in maize

and reported that maximum grain yield was obtained by number of kernels per row

followed by the plant height and ear length. Path coefficient revealed that positive direct

effect was observed on grain yield of plant height and 100 grain weight.

Singh et al. (1999) investigated correlation and path coefficient analysis in maize. They

observed positive and direct effects on grain yield by kernel rows per ear, plant height and

ear diameter.

Torun and Koycu (1999) investigated the effect of yield contributing traits on grain yield

of plant by using correlation and path coefficient analysis. He observed that kernel per ear

and ear length had positive direct effects on grain yield on per plant basis.

Netaji et al. (2000) investigated the result of correlation and path coefficient analysis in

maize. They concluded that seed yield was significantly associated with all yield related

characteristics except days to 50% tasseling and silking. Maximum variability was

observed for plant height followed by ear height. It was also observed that numbers of

kernels per row had positive direct effects on grain yield.

Ries et al. (2000) reviewed the effects of increased levels of ultraviolet radiation on

genome stability of different plant species. Increased exposure to ultraviolet radiations by

using sun stimulators caused increase in homologous rearrangements of tobacco and

Arabidopsis DNA by elevated expression of Rad51 gene which involved in major DNA

repairing pathways. Mutated plants of Arabidopsis missed cyclobutane pyrimidine dimers

in recombination as compared to wild type in elevated UV-B levels. It was concluded that

DNA recombination pathways were involved in repairing DNA lesions caused by elevated

UV-B levels. So it was forecasted that in this century depletion of stratosphere layer of

22

atmosphere can affect genomic stability of plants due to increase in levels of harmful

ultraviolet radiations.

Vigouroux et al. (2001) studied the mutation rate for maize dinucleotide

microsatellites which was 7.7 × 10-4 mutations per generations. They estimated the upper

bound of the rate for microsatellites with repeat motifs of greater than 2 bp which was equal

to 5.1 × 10-5 mutations per generation. It was observed that many factors contributed to the

variation among the reported rates including the average length of microsatellites alleles,

length of the repeat motif, base composition of the repeat motifs and differences in reliable

DNA replication among the individuals of living objects. One important thing which was

found during study, there was no mutations among the loci with repeat motifs of more than

2 bp in length as compared to 70 mutations in loci with dinucleotide repeats.

Cheng et al. (2001) used correlation and path coefficient analysis in 90 crosses of maize

hybrids. Total ten important agronomic characters related to grain yield showed positive

correlation. Results showed that ear length, ear diameter number of kernel rows per ear had

positive direct effects on final yield of plants. It was concluded that in breeding programs

ear length must be given first priority during selection for hybrid development.

Umakanth and Khan (2001) investigated correlation and path coefficient analysis on yield

and yield related traits in maize. They observed that grain yield had positive correlation

with plant height and ear diameter while path coefficient analysis revealed that plant height

had maximum positive direct effects at genotypic level. Ear length, seed weight and ear

diameter have positive direct effects as well as indirect effects on yield through other

characters.

Viccinil and De-Carvalho (2001) carried out a study to standardize an induction

strategy of chromosome variations in maize inbred line L-869. They used irradiated pollen

for fertilization. Germinated seed cells showed abnormal anaphase and telophase stages. It

was observed that as the dosage rate increased the number of abnormalities was also

increased.

Christove et al. (2004) obtained three Super Stiff Stalk (SSS) inbred lines and one

Lancaster inbred line of maize by chemical mutagenesis followed by mutation breeding.

These lines were chosen due to improved GCA and SCA for grain yield and these lines also

showed shift in flowering time. The inbred lines were defined as mutant line with the

23

application of SSR markers, these lines also showed diverse behavior from classical

breeding inbred lines.

De-Oliveira and Viccini, (2004) carried out a program to obtain maize plants with

altered chromosome number. Maize seed were pre-soaked in five concentrations of

metronidazole and again all this material (pre-soaked seeds) were subjected to four

radiation doses. Small part of the seed was used for cytological study and the remaining

planted for survival analysis. During cytological analysis, it was observed that the

occurrence of anaphases with bridges and fragments. The chromosome alterations were

observed in meristemtic cells of M1 progeny which was also verified in M2 generation,

although in lower number. Quantitative reduction of bridges and fragments in M2

generation was also observed.

Kharkwal et al. (2004) reviewed that 2252 mutant varieties of crop have been

developed including cereals, oilseed, pulses, vegetables, fruits, fibers and ornamentals by

the end of 20th century. Most of the mutant varieties were developed by using physical

mutagens. A wide range of character have been improved through mutation breeding

including plant architecture, yield, flowering, maturity duration, quality and tolerance

against biotic and abiotic stresses. Induced mutagens are gaining importance in plant

molecular biology. Mutagens are used as a major tool to identify and isolate the genes.

These are also used to study their structure and function.

Casati and Walbot, (2005) studied that UV-B radiation is an important component

to induce flavonoid in maize landraces at high altitudes. In natural environment, landraces

at high altitudes received much higher UV-B influence as compared to the plants at lower

altitudes. Accumulation of two flavonoids: maysin and its biosynthetic precursor

rhamnosylisoorientin are regulated by UV-B. It was observed that concentration of maysin

and rhamnosylisoorientin were higher in seedling leaves than in subsequent leaves. Highest

concentration of flavonoids was detected in silks. It was found that inbred line at lower

latitude such as W23 showed very low concentration of flavones in response to UV-B

radiation as compare to the landraces at high altitude.

Sachs, (2005) reported that maize as a model plant to study the principles of

inheritance because of variation. Mutagenesis is a phenomenon by which one can induce

mutation in plants through mutagens. Recently large scale mutagens has been developed

which are being used to identify new mutants by forward and reverse genetic tools.

24

Naito et al. (2005) published that mostly radiation-induced mutation were not

transferred to the next generation in Arabidopsis thaliana. Mostly mutants induced with

irradiation with gamma rays or carbon ions carried a very large deletions of up to > 6 Mbp,

the majority of which were not transferred to the next generation. But the results showed

that the mutants containing only 1 or 4-base pair deletions were found in the next progeny.

It was also suggested that the non-transmissibility of the large deletions may be due to the

deletion of the particular region that holds specific genes vital for the gamete development

or viability.

Lau et al. (2006) applied four different irradiation UV-B doses to maize plants, it

was found that flavonoids accumulated among the isogenic lines in response to UV-B

radiation. Photosynthetic activity was inhibited in C4 plants due to the UV-B radiations.

Weil and Monde, (2007) suggested maize as one of the most important genetic

system for studying plant biology and very important model system for the grasses; to study

all this, the main key is wide range of mutations. Mutations can be induced in to its genome.

They reviewed the current uses of mutagens in maize, including wide range of endogenous

transposable elements, chemical mutagens, irradiation as well as RNA-i silencing. Through

induced mutation, large numbers of mutant lines are available to researchers now.

Jacobsen and Schouten (2007) reviewed that the alpha and omega source of genetic

variation is mutation. At the genic level, mutations are mostly recessive and therefore

always found in chimeric form. So this problem can be solved in seed propagated crops

through sexual cycle in homozygous condition and it is not possible in heterozygous

vegetatively propagated crops. Therefore, in auto-tetraploid potato, only few mutations

have been used. But in diploid apple the spontaneous mutations leading to improved

cultivars.

Ojiewo et al. (2007) induced the mutagenesis in African nightshade which is

traditional leafy herbs and vegetables in Africa and South East Asia. This highly nutritious

vegetable mostly produce low yield owing to the competition with the fruit and seed setting.

Induction of male sterility in African nightshade helped to eliminate fruit and seed setting.

25

Pilu et al. (2007) studied that br2 mutation in maize B73 line not only improved the

length of the internodes but also altered the structure of leaf as well. Novel mutant Br2-

23/br2-23 heterozygotes showed intermediate phenotype of the plant like plant height, ear

height and leaf angle. Mutation also effect the midrib area of the leaf, leaf epidermal cells

and stomatal guard cells in brachytic leaves. It was found that the br2-23 specific amplified

fragment is shorter than in wild type maize, designating probably deletion of the br2-23/

coding regions.

Al-Qurainy and Khan, (2009) suggested that chemical mutagens have become an

important tool in crop improvement. The mutant plants which were treated with sodium

azide showed tolerance against stress, longer shelf life and reduced agronomic inputs as

compared to the normal plants. The selection was done on morphological, biochemical and

DNA based markers.

Jain. (2010) studied that mutation is very helpful for desirable mutants with useful

agronomic traits, abiotic and biotic stress tolerant crop can be developed within a shortest

possible time. Mutation is very useful tool to develop new mutant crops for geometrically

growing population of the world. Genomic tool and mutation are very helpful to function

under climate change and limited arable land. The major advantage is to isolate multiple

trait mutant through induced mutation as compared to spontaneous and transgenic

approaches. It is found that the use of mutagenesis with the plant tissue culture and length

of culture in cereal crops could generate the genetic variability. It is suggested that the new

techniques enable the man for reverse selection of single point mutations with TILLING

technique. The increasing number of isolated genes and the formation of transformation

protocols that do not leave marker genes behind but it provides an opportunity to improve

plant breeding while remaining within the gene pool of the classical breeder or mutation

breeding.

Wu et al. (2010) studied the effect of mutation in cauliflower and sprout which was

induced during the space flight. Satellite orbited the earth for 18 days and after returning to

earth, the seeds were sown to check the phenotypic behavior, mutation rate and its

frequency. Among 12 cauliflower plants, two plants showed significant differences

phenotypically. Both plants showed changes in size of the plant and weight of the flower

head. It was found that DNA damages in some genes during the space flight and some

26

changes also inherited from parents to offspring‟s. Plants showed resistance against the

disease like black rot attack.

Tanaka et al. (2010) reviewed the whole scenario of mutation; its effect, lethality

rate, nature of mutation, rate and spectrum of mutation phenotype in higher plants. Ion

beam was used to develop disease resistant line in higher plants. Because ion beams showed

high mutation frequency due to helium ions and carbon ions produced 20 fold higher

mutation frequency as compare to the electron. To produce efficient and novel mutants, ion

beams were very effective to induce high mutation frequency and broad mutation spectrum.

PCR and sequencing analysis showed that half of all mutants possessed large DNA

alterations while all other had point mutations. The plausible fact of ion beam mutation; it

produced limited amount of large irreparable damages to DNA, resulting in production of

null mutations.

Yang et al. (2011) carried out a study to screen an effective dosage combination of

gamma ray and NaN3 for the induction of mutation in maize calli. Maize calli were treated

with physical (60Co) and chemical (NaN3) mutagens. It was observed that for the induction

of mutation in maize calli, the combination of 20 Gy of gamma-ray and 1 mmol/L of NaN3

was the most effective dosage. By complementation test and DNA sequence analysis, it

was observed that the mutation in three endosperm mutant lines with super sweet phenotype

was found in exon 14 of gene sh2 which encodes adenosine diphosphate glucose

pyrophosphorylase.

Vigouroux et al. (2014) studied mutation rate for 142 microsatellite loci in maize

because it is very important tool for plant breeding, genetics and also helpful for evolution.

Mutation rate in dinucleotide repeat motif, 7.7× 10-4 was observed. Mutation was not

observed in any microsatellites with repeat motifs. Between progenitor allele and mutation

rate, a positive correlation was found.

Chapter 3 Materials and methods

Present studies were carried out in research area of the department of Plant breeding and

Genetics, University of agriculture, Faisalabad, during summer 2013. The experimental

material comprised of maize variety Sultan which was treated with four doses of gamma

irradiation which are as follow

T0 : Normal

27

T1 : 20 Gy

T2 : 40 Gy

T3 : 60 Gy

T4 : 80 Gy

Dry seeds were treated with above mentioned doses of gamma rays at Nuclear Institute of

Agriculture and Biology Faisalabad, using Cobalt -60 as a mutagenic agent. Seeds were

dibbled in the field. Experiment was laid out in randomized complete block design, with

two replications. Row to row and plant to plant distances were 75cm and 25 cm

respectively. Recommended cultural and agronomic practices were applied throughout the

growing period of the crop. Observations on all plants were recorded on individual plant

basis for following morphological characteristics.

Plant height (cm):

At physiological maturity, the height of all plants was measured in centimeters

using measuring tape on individual plant basis. Height was measured from ground level to

tip of tassel in SI unit.

Days to silking:

Days to silking were calculated when silks start appearing by deducting it from date

of sowing on individual plant basis.

Days to tasselling:

Days to tasselling were counted when tassels start appearing. Data was recorded on

individual plant basis with a difference from date of sowing to date of tasseling.

Number of grain rows per cob:

Number of grain rows per cob were counted either even or odds in mutated and in

normal plants at physiological maturity.

Cob length (cm):

28

Length of each cob was measured on individual plant basis and average was

calculated. Length was measured with the help of measuring scale from the base to tip of

the cob.

Number of cobs per plant:

At maturity number of cobs per plant were counted on individual plant basis.

Mean diameter of the cob:

Mean diameter of the cob was calculated by using digital caliber. Diameter of the

cob was measured on three points (top, middle and bottom of the cob) then the mean data

was wrote down for further use in the research analysis.

Number of grains per row:

Number of grains were recorded manually from each row of the cob and average of

all the rows per cob were calculated.

Number of grains per cob:

Number of seeds from each cob was counted and average was calculated as a

representative of number of seeds per plant.

Grain weight per cob:

Grain weight per cob was measured by using weighing balance. Each cob was

thrashed and weighed separately.

100 Grain weight (g):

100 seed weight was calculated by randomly selecting 100 seeds per plant and

weighed on electronic balance.

Grain yield per plant:

Weight of seeds harvested from plants was measured in grams using electronic balance and

was recorded as yield per plant.

Statistical analysis

29

The data of each character was statistically analyzed for frequency distribution,

summary statistics and histogram by using statistics software 8.1. Frequency distribution

and histogram were used to elaborate the behavior of individual plant in a population under

different treatments. Variability is typically observed by the standard error of the mean

(Bruke et al, 1988).

Summary statistics was used to summarize the set of recorded observations, in order

to elaborate the largest amount of information into a simpler form.

Chapter 4 Results and Discussion

4.1. Histogram, summary statistics and frequency distribution:

Frequency provides a simple interface for maintaining counts and percentage of

discrete values. It is an organized tabulation and geographical representation of the number

of individuals in each category on the scale of measurement. It shows whether the

observation are high or low and also whether they are spread on one area or concentrated

out across the entire scale. Thus, it offers to represent a picture of how the individual

observations are distributed in the measurement scale. To make raw data in to

comprehensive form, the frequency distribution tables and graphs play important role to

summarize into more compact and interpret table form (Manikandan, 2011).

In frequency distribution, the cumulative frequency is used to limit the number of

observations that lie above or below the data set. The cumulative frequency is calculated

by using frequency distribution table, which can be constructed directly from the data set.

The histogram is a bar of frequency distribution in which the widths of the bar are

related to the classes in which variables has been spread in the raw data and the heights of

the bars are proportional to the class frequencies.

30

4.1.1. Plant height:

Summary statistics for the plant height showed variation between the treatments of

different gamma irradiations. Mean values for the plant height were 137.33 cm in normal

conditions, 133.36 cm at 20 gray, 116.18 cm at 40 gray, 111.57 cm at 60 gray and 107.39

cm at 80 gray gamma radiations. Maximum plant height 192 cm was observed at 20 gray

and minimum value for plant height 45 cm was observed at 20 gray (Table 4.1.1.1). It

showed that irradiation with lower doses of gamma rays significantly improves the

vegetative growth (20 gray) while higher doses proved depressing behavior in 60 Gray ad

80 Gray (142 cm and 151cm plant height respectively). The gamma radiations are the

ionizing radiations which cause damage to DNA and induce mutation in living objects and

more harmful than any other, like UVs radiations. These radiations have disproportionally

damaging effect on higher and lower plants. These radiations showed effects on cell

photosynthetic activity which ultimately lead towards inappropriate growth of the plant

(Jansen et al., 1998). As in the Table 4.1.1.1, the range of plant height showed that different

doses of irradiation brought changes in genetic material which effect randomly.

Coefficients of variation were 16.04 for the plant height in normal conditions, 22.42 at 20

gray, 24.78 at 40 gray, 15.14 at 60 gray and 20.80 at 80 gray. According to the frequency

distribution value, plant height ranged from 78 to 185 cm in normal conditions as in Table

4.1.1.2. As in Figure 4.1.1.1, histogram showed that 2 plants had 77 cm height and 5 plants

had 185 cm height. But most of the plants had 131 cm height. it showed the variation present

within a trait. Plant height ranges from 45 to 192 cm values due to gamma irradiation which

brought genetic changes in genetic material at the dose of 20 gray (Table 4.1.1.3). Overall

the gamma rays affected the genome of the maize as was observed in case of finger millet;

31

after the treatment of seed of finger millet with the gamma rays doses, it was found that

shoot length of the finger millet was reduced as compared to the normal plants (Ambavane

et al., 2014). But in plant height of the maize, the mutagenic effectiveness and its efficiency

behaved in both ways i:e positively and negatively. As in histogram curve, 1 plant has 45

cm height and only 1 plant has 195 cm height (Figure 4.1.1.2). Both plants are poles apart

due to mutagenic changes in genetic material. Maximum plant height was observed 160 cm

at 20 gray and minimum plant height 45cm at 20 gray. In Table 4.1.1.4, frequency

distribution of plant height value ranged from 60 to 160 cm at the dose of 40 gray. As in

Figure 4.1.1.3, 2 plant had 69 cm height and 1 plant had maximum height 160 cm height at

40 gray due to mutagenic changes in the genetic material of the plants. Frequency

distribution for plant height at 60 gray shows that frequency values range from 98 to 142

cm as in Table 4.1.1.5. Histogram curve for the plant height at 60 gray revealed that 1 plant

had 98 cm height, 2 plants had 100 cm height, 1 plant had 104 cm height, 1 plant had 109

cm height, 1 plant had 128 cm height and 1 plant had 142cm height (Figure 4.1.1.4).

Frequency distribution value for the plant height ranged from 57 to 151cm at 80 gray (Table

4.1.1.6). It is also presented in histogram curve in Figure 4.1.1.5. Plant height of the maize

crop was reduced in acute doses of gamma radiations as was explained by Singh and

Balyon, 2009; the plant height of bread wheat reduced due to mutagenesis with gamma

radiations. Irradiation with lower doses of gamma rays significantly improved the

vegetative traits. The overall long-term changes in plant development and its growth which

ultimately effect the plant height may be attributed to changes in plant genome as reported

earlier (Jan et al., 2011).

Table 4.1.1.1. Summary statistics for final height of maize under different treatments.

Normal 20 Gray 40 Gray 60 Gray 80 Gray

Low 95% CI 132.13 126.06 106.72 95.95 101.11

Mean 137.33 133.36 116.18 111.57 107.39

Up 95% CI 142.53 140.65 125.65 127.19 113.68

SD 23.41 29.90 28.79 16.89 22.35

Variance 540.37 894.11 829.24 285.29 499.32

SE Mean 2.57 3.65 4.67 6.38 3.13

C.V. 16.04 22.42 24.78 15.14 20.80

32

Minimum 78.00 45.00 60.00 98.00 57.00

Median 136.00 135.00 124.00 104.00 103.00

Maximum 185.00 192.00 160.00 142.00 151.00

Table 4.1.1.2. Frequency distribution for the final plant height without irradiations (Control).

Value Frequency Percentage Cumulative

Frequency

Cumulative

Percent

78 2 2.3 2 2.3

90 4 4.7 6 7.0

100 2 2.3 8 9.3

104 2 2.3 10 11.6

119 2 2.3 12 14.0

120 2 2.3 14 16.3

122 2 2.3 16 18.6

124 2 2.3 18 20.9

125 2 2.3 20 23.3

126 4 4.7 24 27.9

128 2 2.3 26 30.2

129 2 2.3 28 32.6

130 6 7.0 34 39.5

133 4 4.7 38 44.2

136 6 7.0 44 51.2

140 6 7.0 50 58.1

143 2 2.3 52 60.5

145 8 9.3 60 69.8

33

147 2 2.3 62 72.1

150 8 9.3 70 81.4

160 2 2.3 72 83.7

165 2 2.3 74 86.0

170 8 9.3 82 95.3

180 2 2.3 84 97.7

185 2 2.3 86 100.0

Total 86 100.0

Table 4.1.1.3. Frequency distribution for the final plant height at 20 Gray (Gamma

Radiation).


Frequency

Cumulative

Percentage

45 1 1.5 1 1.5

69 1 1.5 2 3.0

70 1 1.5 3 4.5

72 1 1.5 4 6.0

81 1 1.5 5 7.5

90 1 1.5 6 9.0

91 1 1.5 7 10.4

93 1 1.5 8 11.9

97 1 1.5 9 13.4

100 2 3.0 11 16.4

102 1 1.5 12 17.9

104 1 1.5 13 19.4

113 1 1.5 14 20.9

114 1 1.5 15 22.4

116 1 1.5 16 23.9

34

119 1 1.5 17 25.4

120 2 3.0 19 28.4

123 2 3.0 21 31.3

125 2 3.0 23 34.3

126 2 3.0 25 37.3

128 2 3.0 27 40.3

130 2 3.0 29 43.3

Continue

131 1 1.5 30 44.8

133 1 1.5 31 46.3

134 2 3.0 33 49.3

135 1 1.5 34 50.7

138 2 3.0 36 53.7

140 4 6.0 40 59.7

145 1 1.5 41 61.2

146 1 1.5 42 62.7

150 1 1.5 43 64.2

152 1 1.5 44 65.7

153 2 3.0 46 68.7

155 4 6.0 50 74.6

157 1 1.5 51 76.1

160 3 4.5 54 80.6

161 1 1.5 55 82.1

164 1 1.5 56 83.6

165 4 6.0 60 89.6

35

167 1 1.5 61 91.0

168 1 1.5 62 92.5

169 1 1.5 63 94.0

170 2 3.0 65 97.0

175 1 1.5 66 98.5

192 1 1.5 67 100.0

Total 67 100.0

Table 4.1.1.4. Frequency distribution for final plant height at 40 Gray (Gamma

Radiation).


Frequency

Cumulative

Percentage

60 2 5.3 2 5.3

67 1 2.6 3 7.9

68 1 2.6 4 10.5

69 1 2.6 5 13.2

70 1 2.6 6 15.8

82 1 2.6 7 18.4

92 1 2.6 8 21.1

97 1 2.6 9 23.7

99 1 2.6 10 26.3

100 2 5.3 12 31.6

105 1 2.6 13 34.2

107 1 2.6 14 36.8

108 1 2.6 15 39.5

114 1 2.6 16 42.1

36

120 2 5.3 18 47.4

123 1 2.6 19 50.0

125 2 5.3 21 55.3

129 1 2.6 22 57.9

132 1 2.6 23 60.5

135 3 7.9 26 68.4

138 1 2.6 27 71.1

139 1 2.6 28 73.7

Continue

140 2 5.3 30 78.9

141 1 2.6 31 81.6

143 1 2.6 32 84.2

144 1 2.6 33 86.8

145 2 5.3 35 92.1

148 1 2.6 36 94.7

155 1 2.6 37 97.4

160 1 2.6 38 100.0

Total 38 100.0

Table 4.1.1.5. Frequency distribution for final plant height at 60 Gray (Gamma Radiation).


Frequency

Cumulative

Percentage

98 1 14.3 1 14.3

100 2 28.6 3 42.9

104 1 14.3 4 57.1

109 1 14.3 5 71.4

37

128 1 14.3 6 85.7

142 1 14.3 7 100.0

Total 7 100.0

Table 4.1.1.6. Frequency distribution for final plant height at 80 Gray (Gamma Radiation).


Frequency

Cumulative

Percentage

57 1 2.0 1 2.0

71 1 2.0 2 3.9

73 1 2.0 3 5.9

75 1 2.0 4 7.8

78 3 5.9 7 13.7

79 1 2.0 8 15.7

82 1 2.0 9 17.6

86 1 2.0 10 19.6

87 1 2.0 11 21.6

89 1 2.0 12 23.5

92 2 3.9 14 27.5

95 1 2.0 15 29.4

96 1 2.0 16 31.4

97 1 2.0 17 33.3

98 2 3.9 19 37.3

99 1 2.0 20 39.2

38

100 3 5.9 23 45.1

102 2 3.9 25 49.0

103 1 2.0 26 51.0

113 2 3.9 28 54.9

115 2 3.9 30 58.8

117 3 5.9 33 64.7

Continue

120 2 3.9 35 68.6

124 1 2.0 36 70.6

125 2 3.9 38 74.5

126 4 7.8 42 82.4

128 1 2.0 43 84.3

129 1 2.0 44 86.3

130 1 2.0 45 88.2

132 1 2.0 46 90.2

141 1 2.0 47 92.2

144 1 2.0 48 94.1

145 2 3.9 50 98.0

151 1 2.0 51 100.0

Total 51 100.0

39

Figure 4.1.1.1: Histogram for final plant height at nor irradiated conditions (Control).

Figure 4.1.1.2. Histogram for final plant height at 20 Gray (Gamma Radiation).

40



41


4.1.2. Days to silking:

Variation between the treatments of different gamma irradiations X1 was observed

for days taken to silking. Mean value for days to silking was 53.44 in non-irradiated, 54.21

at 20 gray, 53.58 at 40 gray, 58 at 60 gray and 53.45 at 80 gray gamma radiations. Ravilla

et al. (1999) and Torun et al. (1999) found significant GCA and SCA effects for days to

silking, grains per cob, cobs per plant, cob length, and 100-seed weight which had

significant direct effects on grain yield. That‟s why days taken to silking ultimately decides

the final yield of the plant. Because failure in fertilization due to the large difference in

emergence of tasseling and silking surely lead towards increased anthesis silky interval

(ASI) and the loss in yield of the plant. Maximum 62 days to silking were observed in

normal conditions and minimum value 57 was observed at 40 gray (Table 4.1.2.1). This

variation showed that different doses of irradiation brought changes in genetic material

which changes the genetic material randomly.

Coefficient of variation was 7.72 for days to silking in non-irradiated conditions,

2.46 at 20 gray, 2.33 at 40 gray, 3.73 at 60 gray and 2.63 at 80 gray. According to the

frequency distribution value, days taken to silking range from 46 to 62 in normal conditions

as in Table 4.1.2.2. It showed the lot of variation within a trait which is also explained in

Figure 4.11.1. Days to silking showed 51 to 58 values due to gamma irradiation which

brought genetic changes due to the effect of mutagen at the dose of 20 gray (Table 4.1.2.3).

42

Histogram curve explained that maximum plants showed inflorescence after 53 days

(Figure 4.1.2.2). There was no silking before 51 days to sowing and after 58 days to sowing

at 20 gray of mutagenic dose. In Table 4.1.2.4, frequency distribution value ranged from

51 to 57 days to silking at the dose of 40 gray. As in Figure 4.1.2.3, days to silking varied

from 51 to 57 at 40 gray due to mutagenic changes in the genetic material of the plants.

Frequency distribution for days to silking at 60 gray shows that frequency values range

from 55 to 61 as in Table 4.1.2.5. Histogram curve for days to silking at 60 gray shows that

plant starts silking after 55 days. It will lead towards early maturity as in Figure 4.1.2.4.

Frequency distribution values for the days to silking ranged from 50 to 58 at 80 gray as in

Table 4.1.2.6. It is also presented in histogram curve in Figure 4.1.2.5. Wenzel et al. (2000)

and Zelleke (2000) revealed that 44 % grain yield was reduced and SCA effects were

observed just because of silking and other yield related component. Rocha et al. (2000);

Umakanth et al. (2000); Desai and

Singh (2001) and Iqbal et al. (2001) observed significant differences in GCA and SCA

effects for different traits including days taken to silking. From above discussion, it can be

concluded that silking is an important component of yield and yield attributes. In present

study, due to mutagenic dose of 40 gray, it was observed that only 57 days taken to silking

as compared to the normal treatment in which 62 days to silking were observed. But other

mutagenic doses also induced mutation in the genome of the maize to develop silking

phenomena earlier as compare to the non-mutant cultivars.

Table 4.1.2.1. Summary statistics for days to silking of maize under different treatments.


Low 95% CI 52.17 53.88 53.17 56.02 53.06

Mean 53.44 54.21 53.58 58.00 53.45

Up 95% CI 54.71 54.53 53.99 59.99 53.85

SD 4.13 1.34 1.24 2.16 1.40

Variance 16.01 1.78 1.55 4.67 1.97

SE Mean 0.63 0.16 0.20 0.82 0.20

C.V. 7.72 2.46 2.33 3.73 2.63

Minimum 46.00 51.00 51.00 55.00 50.00

43

Median 54.00 54.00 54.00 58.00 54.00

Maximum 62.00 58.00 57.00 61.00 58.00

Table

44

4.1.2.2. Frequency distribution for days to silking at non-irradiated conditions

(Control).


Frequency

Cumulative

Percentage

46 4 4.7 4 4.7

47 4 4.7 8 9.3

48 4 4.7 12 14.0

49 4 4.7 16 18.6

51 14 16.3 30 34.9

52 8 9.3 38 44.2

53 4 4.7 42 48.8

54 14 16.3 56 65.1

55 6 7.0 62 72.1

57 8 9.3 70 81.4

58 4 4.7 74 86.0

59 8 9.3 82 95.3

62 4 4.7 86 100.0

Total 86 100.0

Table

45

4.1.2.3. Frequency distribution for days to silking at 20 Gray (Gamma Radiation).

Value Freq Percent Freq Percent

51 2 3.0 2 3.0

52 5 7.5 7 10.4

53 9 13.4 16 23.9

54 25 37.3 41 61.2

55 16 23.9 57 85.1

56 8 11.9 65 97.0

57 1 1.5 66 98.5

58 1 1.5 67 100.0

Total 67 100.0

Table 4.1.2.4. Frequency distribution for days to silking at 40 Gray (Gamma Radiation).


Frequency

Cumulative

Percentage

51 2 5.3 2 5.3

52 5 13.2 7 18.4

53 9 23.7 16 42.1

54 16 42.1 32 84.2

55 4 10.5 36 94.7

56 1 2.6 37 97.4

57 1 2.6 38 100.0

Total 38 100.0

Table

46

4.1.2.5. Frequency distribution for days to silking at 60 Gray (Gamma Radiation).


Frequency

Cumulative

Percentage

55 1 14.3 1 14.3

56 1 14.3 2 28.6

57 1 14.3 3 42.9

58 1 14.3 4 57.1

59 1 14.3 5 71.4

60 1 14.3 6 85.7

61 1 14.3 7 100.0

Total 7 100.0

Table 4.1.2.6. Frequency distribution for the days to silking at 80 Gray (Gamma Radiation).


Frequency

Cumulative

Percentage

50 1 2.0 1 2.0

51 3 5.9 4 7.8

52 8 15.7 12 23.5

53 12 23.5 24 47.1

54 18 35.3 42 82.4

55 7 13.7 49 96.1

56 1 2.0 50 98.0

58 1 2.0 51 100.0

Total 51 100.0

Table

47

48

Figure 4.1.2.1. Histogram for days to silking at non-irradiated conditions (Control).

Figure 4.1.2.2. Histogram for days to silking at 20 Gray (Gamma Radiation).

49



\

50


4.1.3. Days to tasseling:

51

Summary statistics for days to tasseling showed variation between the treatments of

different gamma irradiations. Mean value for days to tasseling was 49.07 in normal

conditions, 50.40 at 20 gray, 50.24 at 40 gray, 54 at 60 gray and 50.96 at 80 gray gamma

radiations. Maximum days to tasseling 56 were observed in normal condition and at 60 gray

and minimum value for days to tasseling 42 was observed in normal conditions as in Table

4.1.3.1. It showed that different doses of irradiation brought changes in genetic material and

environment helped to induce tasseling phenomena earlier as compared to the normal

treatment. Wenzel et al. (2000) and Zelleke (2000) concluded that 44% grain yield was

reduced and significant SCA effects were shown by plant height, days taken to tasseling,

silking, grain rows per cob, cobs per plant and grain yield per plant. In all above, the days

taken to tasseling is also an important component of fertilization. That‟s why changes in

days taken to tasseling lead towards the success or failure of the final seed setting which is

a main component of yield as well.

Coefficient of variation was 8.85 for days to tasseling in normal conditions, 2.85 at

20 gray, 3.32 at 40 gray, 2.83 at 60 gray and 3.66 at 80 gray. According to the frequency

distribution value, days to tasseling ranged from 42 to 56 in normal conditions (Table

4.1.3.2). It showed lot of variation within a trait which is explained in Figure 4.1.3.1. Days

to tasseling showed 47 to 53 values due to gamma irradiation which brought genetic

changes in genetic material at the dose of 20 gray as in Table 4.1.3.3. Histogram curve

shows that only 6 plants are poles apart but remaining plants present between the ranges of

47 to 53 (Figure 4.1.3.2). Maximum days to tasseling was 53 at 20 gray and minimum days

to tasseling was 47 at 20 gray. In Table 4.1.3.4, frequency distribution value fluctuated

from 47 to 53 days to tasseling at the dose of 40 gray. As Figure 4.1.3.3, explains that days

to tasseling vary from 47 to 53 at 40 gray due to mutagenic changes in the genetic material

of the plants (days to tasseling period was reduced in mutants). Frequency distribution for

days to tasseling at 60 gray shows that frequency values range from 52 to 56 as explained

in Table 4.1.3.5. Histogram curve for the days to tasseling at 60 gray shows that only 1

plant starts tasseling after 55 days but all other plants ranged between 50 to 53 days to

tasseling period (Figure 4.1.3.4). Frequency distribution values for the days taken to

tasseling ranged from 47 to 55 at 80 gray (Table 4.1.3.6). It is also explained in histogram

curve in Figure 4.1.3.5. As above discussed, the mutant material showed slower growth as

compared to the normal maize plant. The same results were also consistent with the idea

that tassel elongation slowed down in mutant (Tassel Seed 6) as compared to the wild maize

52

plant (Irish, 1997). Prakash et al. (2004) and Zhou et al. (2004) estimated GCA and SCA

effects for days taken to 50% tasseling and other yield related components. But additive

type of gene action was also observed for day to tasseling. As above discussed, then it can

be concluded that polygenic trait like tasseling is controlled by many genes except one

dominant gene. In present study, it was found that mutagenic doses of 20 gray and 40 gray

were very effective to induce mutation in polygenic trait of tasseling and helped to minimize

the days taken to tasseling. So at the end, it would help to fulfill the dream of early maturity

of maize crop.

Table 4.1.3.1.Summary statistics for days to tasseling of maize under different treatments.


Low 95% CI 48.73 50.05 49.69 52.59 50.44

Mean 49.07 50.40 50.24 54.00 50.96

Up 95% CI 49.41 50.75 50.78 55.41 51.48

SD 4.35 1.42 1.67 1.53 1.86

Variance 18.87 2.06 2.78 2.33 3.48

SE Mean 0.46 0.17 0.27 0.58 0.26

C.V. 8.85 2.85 3.32 2.83 3.66

Minimum 42.00 47.00 47.00 52.00 47.00

Median 49.00 51.00 50.00 54.00 51.00

Maximum 56.00 53.00 53.00 56.00 55.00

Table

53

4.1.3.2.Frequency distribution for days to tasseling at non-irradiated conditions

(Control).


Frequency

Cumulative

Percentage

42 4 4.7 4 4.7

43 6 7.0 10 11.6

44 12 14.0 22 25.6

45 4 4.7 26 30.2

46 4 4.7 30 34.9

48 4 4.7 34 39.5

49 10 11.6 44 51.2

50 6 7.0 50 58.1

51 4 4.7 54 62.8

52 8 9.3 62 72.1

53 10 11.6 72 83.7

54 6 7.0 78 90.7

55 2 2.3 80 93.0

56 6 7.0 86 100

Total 86 100.0

4.1.3.3. Frequency distribution for days to tasseling at 20 Gray (Gamma Radiation).


Frequency

Cumulative

Percentage

47 1 1.5 1 1.5

48 7 10.4 8 11.9

Table

54

49 11 16.4 19 28.4

50 11 16.4 30 44.8

51 23 34.3 53 79.1

52 10 14.9 63 94.0

53 4 6.0 67 100.0

Total 67 100.0

Table 4.1.3.4. Frequency distribution for days to tasseling at 40 Gray (Gamma Radiation).


Frequency

Cumulative

Percentage

47 3 7.9 3 7.9

48 1 2.6 4 10.5

49 10 26.3 14 36.8

50 7 18.4 21 55.3

51 8 21.1 29 76.3

52 5 13.2 34 89.5

53 4 10.5 38 100.0

Total 38 100.0

4.1.3.5. Frequency distribution for days to tasseling at 60 Gray (Gamma Radiation).


Frequency

Cumulative

Percentage

52 2 28.6 2 28.6

54 2 28.6 4 57.1

55 2 28.6 6 85.7

Table

55

56 1 14.3 7 100.0

Total 7 100.0

Table 4.1.3.6. Frequency distribution for days to tasseling at 80 Gray (Gamma Radiation).


Frequency

Cumulative

Percentage

47 2 3.9 2 3.9

48 5 9.8 7 13.7

49 6 11.8 13 25.5

50 2 3.9 15 29.4

51 14 27.5 29 56.9

52 13 25.5 42 82.4

53 6 11.8 48 94.1

54 2 3.9 50 98.0

55 1 2.0 51 100.0

Total 51 100.0

56

Figure 4.1.3.1. Histogram for days to tasseling at non-irradiated conditions (Control).

Figure 4.1.3.2. Histogram for days to tasseling at 20 Gray (Gamma Radiation).

57



58

Figure 4.1.3.5. Histogram for days to tasseling at 80 Gray (Gamma Radiation)

4.1.4. Number of grain rows per cob:

Number of grain rows per cob exhibited variation between the treatments of

different gamma irradiations. Mean value for the number of grain rows per cobs per plant

59

was 13.78 in normal conditions, 12.10 at 20 gray, 14.97 at 40 gray, 10.14 at 60 gray and

11.94 at 80 gray gamma radiations. Kahkim et al. (1998); Mather et al. (1998); Sanvicente

et al. (1998); Singh et al. (1998); Almeida et al. (1999) and Nass et al. (2000) concluded

that number of grain rows per cob had significant correlation with the yield per plant. As

above mentioned that mean value of mutant seed at 40 gray showed higher number of grain

rows per cob as compared to the normal plants, surely those mutant plants with higher

number of grain rows per cobs will lead towards the higher yield per plant. Maximum

number of grain rows per cob were observed at 40 gray and minimum value for number of

rows per cob were observed at 60 gray as in Table 4.1.4.1. This shows that different doses

of radiation brought changes in genetic material which results in changes in number of rows

per cobs randomly. Number of grain rows per cob is an important morphological trait which

helps us to estimate the total production/yield of the maize crop.

Coefficient of variation was 16.75 for number of grain rows per cob in normal

condition, 24.05 at 20 gray, 27.58 at 40 gray, 18.38 at 60 gray and 27.54 at 80 gray.

According to the frequency distribution value, it ranged from 8 to 20 in normal condition.

It also showed that 2 cobs have eight grain rows but 2 cobs have ten rows, 33 cobs have 12

rows, 22 cobs have 14 rows, 20 cobs have 16 rows, 4 cobs have 18 rows and 2 cobs have

20 rows as in Table 4.1.4.2 and it is also explained in Figure 4.1.4.1. Number of grain rows

per cob showed 5 to 20 value due to gamma radiation at the dose of 20 gray (Table 4.1.4.3).

Histogram curve for number of grain rows per cob at 20 gray showed that 1 cob have 5

rows, 2 cobs have 6 rows, 5 cobs have 8 rows, 12 cobs have 10 rows, 15 cobs have 12 rows,

18 cobs have 16 rows, 2 cobs have 18 rows and 1 cob has 20 rows as in Figure 4.1.4.2. In

Table 4.1.4.4, frequency distribution value range from 6 to 18 at the dose of 40 gray. As in

Figure 4.1.4.3, histogram shows that 3 cobs have 6 row, 9 cobs have 8 rows, 1 cob has 9

rows, 5 cobs have10 rows, 10 cobs have 12 rows, 1 cob has 13 rows, 5 cobs have 14 rows,

2 cobs have 16 rows and 1 cob has 18 rows at 40 gray due to mutagenic changes in the

genetic material of the plants. Frequency distribution for the number of grain rows per cob

at 60 gray showed frequency values; which ranged from 8 to 12 (Table 4.1.4.5). Histogram

curve for the number of rows per cob at 60 gray showed that 2 cobs have 8 rows, 1 cob has

9 rows, 1 cob has 10 rows and 3 cobs have 12 rows (Figure 4.1.4.4). Frequency distribution

value for the number of grain rows per cob ranged from 0 to 18 at 80 gray in Table 4.1.4.6.

It was observed that 2 cobs had 0 rows due to severe effect of mutagen that‟s why abnormal

cobs were developed. And 2 cobs have 8 rows, 12 cobs have 10 rows, 1 cob has 11 rows,

14 cobs have 12 rows, 14 cobs have 14 rows, 5 cobs have 16 rows and 1 cob has 18 rows

60

also presented in histogram curve in Figure 4.1.4.5. Ali et al, 2014 reported that number of

grain rows per cob is an important sign to increase the yield per plant. If the number of rows

per cob is increased then it will lead to increase the total yield of the crop, hence it will help

to enhance the food security in the world. As above discussed that normal seed material

have maximum 20 grain rows but the seed which were mutated at 40 gray showed

maximum 22 rows per cob. The observed increase in number of grain rows per cob due to

the effect of mutation, surely this will help to increase the yield per plant.

Table 4.1.4.1. Summary statistics for number of grain rows per cob of maize under different

treatments.


Lo 95% CI 13.29 11.39 10.00 8.42 11.02

Mean 13.78 12.10 14.97 10.14 11.94

Up 95% CI 14.28 12.81 12.00 11.87 12.86

SD 2.31 2.91 3.04 1.87 3.29

Variance 5.33 8.46 9.16 3.48 10.82

SE Mean 0.25 0.36 0.49 0.71 0.46

C.V. 16.75 24.05 27.58 18.38 27.54

Minimum 8.00 5.00 6.00 8.00 0.00

Median 14.00 12.00 14.00 10.00 12.00

Maximum 20.00 18.50 22.00 12.00 18.00

Table 4.1.4.2. Frequency distribution for number of grain rows per cob at non-irradiated

conditions (Control).


Frequency

Cumulative

Percentage

8 2 2.4 2 2.4

10 2 2.4 4 4.7

61

12 33 38.8 37 43.5

14 22 25.9 59 69.4

16 20 23.5 79 92.9

18 4 4.7 83 97.6

20 2 2.4 85 100.0

Total 85 100.0

Table 4.1.4.3. Frequency distribution for number of grain rows per cob at 20 Gray (Gamma

Radiation).


Frequency

Cumulative

Percentage

5.00 1 1.5 1 1.5

6.00 2 3.0 3 4.5

8.00 5 7.5 8 11.9

8.50 1 1.5 9 13.4

9.00 1 1.5 10 14.9

9.50 1 1.5 11 16.4

10.00 12 17.9 23 34.3

11.00 1 1.5 24 35.8

12.00 15 22.4 39 58.2

Continue

13.00 1 1.5 40 59.7

14.00 18 26.9 58 86.6

16.00 6 9.0 64 95.5

18.00 2 3.0 66 98.5

20.00 1 1.5 67 100.0

62

Total 67 100.0


Radiation)


Frequency

Cumulative

Percentage

6 3 7.9 3 7.9

8 9 23.7 12 31.6

9 1 2.6 13 34.2

10 5 13.2 18 47.4

12 10 26.3 28 73.7

13 1 2.6 29 76.3

14 5 13.2 34 89.5

15 1 2.6 35 92.1

16 2 5.3 37 97.4

18 1 2.6 38 100.0

Total 38 100.0


Radiation)

Value Frequency Percent Cumulative

Frequency

Cumulative

Percentage

8 2 28.6 2 28.6

9 1 14.3 3 42.9

63

10 1 14.3 4 57.1

12 3 42.9 7 100.0

Total 7 100.0


Radiation)


Frequency

Cumulative

Percent

0 2 3.9 2 3.9

8 2 3.9 4 7.8

10 12 23.5 16 31.4

11 1 2.0 17 33.3

12 14 27.5 31 60.8

14 14 27.5 45 88.2

16 5 9.8 50 98.0

18 1 2.0 51 100.0

Total 51 100.0

64

Figure 4.1.4.1. Histogram for number of grain rows per cob at non-irradiated conditions

(Control).

Figure 4.1.4.2. Histogram for number of grain rows per cob at 20 Gray (Gamma Radiation).

65



66


4.1.5. Cobs length:

Summary statistics for cobs length showed variation between the treatments of different

gamma irradiations. Mean value for cob length was 13.16 cm in normal conditions, 10.73

cm at 20 gray, 9.41 cm at 40 gray, 10.28 cm at 60 gray and 12.27 cm at 80 gray gamma

67

radiations. Chapman et al. (1997) and Tusuz and Balabanli (1997) reported that cob length

showed low broad sense heritability while grain yield was positively and significantly

correlated with cob length. Kahkim et al. (1998); Mather et al. (1998); San vicente et al.

(1998) concluded that grain yield had a positive and significant genotypic correlation with

number of grain per cob, number of grain rows per cob, cob length, 100seed weight and

grain oil contents. Ravilla et al. (1999) and Torun et al. (1999) found significant GCA and

SCA effects were found for grains per cob, cobs per plant, cob length, and 100-seed weight

had significant direct effects on grain yield. All above discussion has reached on one point;

cob length directly influence the yield of the maize crop. Maximum value of cobs length

23cm was observed at 20 gray which will surely lead towards the higher yield of the crop

and minimum value for cobs length 19cm was observed at 40 gray (Table 4.1.5.1). This

showed that different doses of irradiation brought changes in genetic material due to

mutagenic effect of different doses. Cob length is an important morphological trait which

helps us to estimate the total production of the maize crop. If the length of the cob is

increased, and if the cob has fertile ovaries on extended area; there will be a chance of

increase in number of grains on the cob.

Coefficient of variation was 31.32 in normal condition, 41.22 at 20 gray, 48.66 at

40 gray, 45.85 at 60 gray and 37.23 at 80 gray. According to the frequency distribution

value, it was ranged from 4 to 20cm in normal conditions. It also showed that maximum

cobs length was 20 cm and minimum cobs length 20 cm (Table 4.1.5.2) and it is also

explained in Figure 4.1.5.1. Cobs length showed 3 to 23cm values due to gamma radiation

which brought genetic changes in genetic material at the dose of 20 gray (Table 4.1.5.3).

Histogram curve at the dose of 20 gray showed that only 1 cob had maximum length 23 cm

and 1 cobs had minimum length 5 cm but mostly cobs had average length 17 cm (Figure

4.1.5.2). In Table 4.1.5.4, frequency distribution value ranged from 2 to 19 cm at the dose

of 40 gray. As in Figure 4.1.5.3, maximum cob length was 19 cm and minimum cobs length

was 2 cm. Frequency distribution for the cobs length at 60 gray shows frequency values

range from 6 to 18cm (Table 4.1.5.5). Histogram curve for the cobs length at 60 gray

showed that 1 cob had 6 cm length, 1 cob had 7 cm length, 2 plant had 8 cm length, 1 plant

had 9 cm length, 1 plant had 16 cm length, and 1 plant has 18 cm length (Figure 4.1.5.4).

Frequency distribution value for the cobs length ranged from 4 to 22 cm at 80 gray (Table

4.1.5.6). It was observed that maximum cob length was 22 cm at 80 gray and minimum

cobs length was 4 cm at 80 gray gamma irradiation, it is also presented in histogram curve

(Figure 4.1.5.5).

68

As above discussed that grain yield was positively correlated with cobs length

(Mather et al. 1998). In present experimental scenario, it can be concluded that mutagens

played a very important and positive role to induce the mutation; cobs length was increased

from 20 cm to 23 cm at the mutagen dose of 20 gray.

Table 4.1.5.1. Summary statistics for cobs length of maize under different treatments.


Low 95% CI 11.89 9.65 7.90 5.92 10.99

Mean 13.16 10.73 9.40 10.28 12.27

Up 95% CI 14.43 11.81 10.90 14.67 13.56

SD 4.13 4.42 4.57 4.72 4.57

Variance 16.997 19.56 20.89 22.24 20.88

SE Mean 0.63 0.54 0.74 1.78 0.64

C.V. 31.32 41.22 48.66 45.85 37.23

Minimum 4.00 3.00 2.00 6.00 0.00

Median 13.00 10.00 9.00 8.00 13.00

Maximum 20.00 23.00 19.00 18.00 22.00

Table

69

4.1.5.2. Frequency distribution for the cobs length without Irradiation conditions

(Control).


Frequency

Cumulative

Percentage

4 2 2.3 2 2.3

6 4 4.7 6 7.0

7 4 4.7 10 11.6

8 4 4.7 14 16.3

9 4 4.7 18 20.9

10 6 7.0 24 27.9

11 2 2.3 26 30.2

12 10 11.6 36 41.9

13 10 11.6 46 53.5

14 2 2.3 48 55.8

15 10 11.6 58 67.4

16 8 9.3 66 76.7

17 4 4.7 70 81.4

18 8 9.3 78 90.7

19 6 7.0 84 97.7

20 2 2.3 86 100.0

Total 86 100.0

4.1.5.3. equency distribution for cobs length at 2


Frequency

Percent

3 1 1.5 1 1.5

Table Fr 0 Gray (Gamma Radiation).

70

4 4 6.0 5 7.5

5 2 3.0 7 10.4

6 4 6.0 11 16.4

7 10 14.9 21 31.3

8 5 7.5 26 38.8

9 3 4.5 29 43.3

10 7 10.4 36 53.7

11 2 3.0 38 56.7

12 2 3.0 40 59.7

13 6 9.0 46 68.7

14 6 9.0 52 77.6

15 4 6.0 56 83.6

16 6 9.0 62 92.5

17 2 3.0 64 95.5

18 1 1.5 65 97.0

20 1 1.5 66 98.5

23 1 1.5 67 100.0

Total 67 100.0



Frequency

Cumulative

Percentage


71

2 1 2.6 1 2.6

3 1 2.6 2 5.3

4 6 15.8 8 21.1

5 2 5.3 10 26.3

6 1 2.6 11 28.9

7 2 5.3 13 34.2

8 5 13.2 18 47.4

9 3 7.9 21 55.3

10 2 5.3 23 60.5

11 4 10.5 27 71.1

12 1 2.6 28 73.7

13 2 5.3 30 78.9

14 2 5.3 32 84.2

15 2 5.3 34 89.5

17 2 5.3 36 94.7

18 1 2.6 37 97.4

19 1 2.6 38 100.0

Total 38 100.0



72


Frequency

Cumulative

Percentage

6 1 14.3 1 14.3

7 1 14.3 2 28.6

8 2 28.6 4 57.1

9 1 14.3 5 71.4

16 1 14.3 6 85.7

18 1 14.3 7 100.0

Total 7 100.0

Table 4.1.5.6. Frequency distribution for cobs length at 80 Gray (Gamma Radiation).


Frequency

Percent

4 1 2.0 2 3.9

6 3 5.9 5 9.8

7 3 5.9 8 15.7

8 5 9.8 13 25.5

9 2 3.9 15 29.4

10 2 3.9 17 33.3

11 1 2.0 18 35.3

12 5 9.8 23 45.1

13 9 17.6 32 62.7

14 5 9.8 37 72.5

15 3 5.9 40 78.4

16 3 5.9 43 84.3

Continue

73

17 1 2.0 44 86.3

18 3 5.9 47 92.2

19 1 2.0 48 94.1

20 1 2.0 49 96.1

22 2 3.9 51 100.0

Total 51 100.0

Figure 4.1.5.1. Histogram for cobs length without irradiation treatments (Control).

74

Figure 4.1.5.2. Histogram for cobs length at 20 Gray (Gamma Radiation).


75



4.1.6. Number of cobs per plant:

76

Summary statistics for number of cobs per plant showed variation between the treatments

of different gamma irradiations. Mean value for number of cobs per plant was 1.023 in

normal conditions, 1.52 at 20 gray, 1.90 at 40 gray, 2.29 at 60 gray and 1.98 at 80 gray

gamma radiations. Maximum 8 cobs per plant was observed at 60 gray and minimum value

for number of cobs per plant was observed 2 in normal condition (Table 4.1.6.1). This

shows that different doses of radiation bring changes in genetic material which results in

changes in number of cobs per plant randomly. Number of cobs per plant is an important

morphological trait which helps us to estimate the total production of the maize crop.

Coefficient of variation was 14.90 for number of cobs per plant in normal condition,

58.71 at 20 gray, 85.90 at 40 gray, 60.38 at 60 gray and 69.59 at 80 gray. According to the

frequency distribution value, it was ranged from 1 to 2 in normal condition. In histogram

curve, it showed that 84 plants had only one cob per plant but 2 plants had two cobs per

plant (Table 4.1.6.2) and it is also explained in Figure 4.1.6.1. Histogram curve for number

of cobs per plant at 20 gray showed that 43 plants had 1 cob per plant, 17 plants had 2 cobs

per plant, 5 plants had 3 cobs per plant, 1 plant had 4 cobs per plant and 1 plant had 6 cobs

per plant (Figure 4.1.6.2). In Table 4.1.6.4, frequency distribution value ranged from 1 to 8

at the dose of 40 gray. In Figure 4.1.6.3 explained that 21 plants had 1 cob per plant, 11

plants had 2 cobs per plant, 3 plants had 3 cobs per plant, 1 plant had 6 cobs per plant, 1

plant had 7 cobs per plant and 1 plant had 8 cobs per plant at 40 gray due to mutagenic

changes in the genetic material of the plants. Frequency distribution for number of cobs per

plant at 60 gray showed frequency values ranged from 1 to 4 (Table 4.1.6.5). Histogram

curve for number of cobs per plant at 60 gray showed that 3 plants had 1 cob per plant, 1

plant had 2 cobs, 1 plant had 3 cobs and 2 plant had 4 cobs per plant out of 7 (Figure 4.1.6.4).

Frequency distribution value for number of cobs per plant ranged from 0 to 7 at 80 gray

(Table 4.1.6.6). It was observed that 1 plant had 0 cobs, 25 plants had 1 cob, 12 plants had

2 cobs, 4 plants had 3 cobs, 7 plants had 4 cobs, 1 plant had 5 cobs and 1 plant had 7 cobs

also presented in histogram (Figure 4.1.6.5). Farkorede and Ayoola (1981); Javed (1987);

Kahkim et al. (1998); Mather et al. (1998); Sanvicente et al. (1998); Singh et al. (1998);

Almeia et al. (1999) and Nass et al. (2000) found a positive and significant genotypic and

phenotypic correlation of grain yield with number of cobs per plant. It shows that cobs per

plant have crucial role with the grain yield. It is a fact that grain yield plant are ultimately

dependent on number of cobs per plant. Debnath and Sarkar (1990); Reddy and Joshi (1990)

and Beck et al. (1990) reported that positive and significant genotypic and phenotypic

77

correlation were between grain yield per plant and cobs per plant, plant height, grain rows

per cob, 100-seed weight, cob length and diameter. As above discussed that number of cobs

per plant are dependable trait and play a very important role in grain yield. Enujeke E. C.

(2013) found that plant sown on spacing of 75 cm × 15 cm had highest number of cobs per

plant than plants sown on wider spacing possibly because narrow spaced crops resulted in

higher plant density and more number of cobs. He also recommended that spacing of 75 cm

× 15 cm resulted in higher grain yield indices of maize, it should be adopted in maize

production. But in present study, the spacing 75 cm × 22.5 cm was adopted by sowing

mutant seed. As above discussed that number of cobs per plant are dependent on number

of factors as describes earlier but different mutagen had also played very crucial role for

the creation of mutation which lead to produce more number of cobs per plant, the 60 gray

dose especially induce this phenomena.

Table 4.1.6.1. Summary statistics for number of cobs per plant of maize under different

treatments.


Low 95% CI 0.98 1.30 1.38 1.02 1.59

Mean 1.023 1.52 1.90 2.29 1.98

Up 95% CI 1.07 1.74 2.46 3.56 2.37

SD 0.16 0.90 1.65 1.38 1.38

Variance 0.03 0.80 2.72 1.91 1.91

SE Mean 0.01 0.11 0.27 0.52 0.19

C.V. 14.90 58.71 85.90 60.38 69.59

Minimum 1.00 1.00 1.00 1.00 0.00

Median 1.00 1.00 1.00 2.00 1.00

Maximum 2.00 6.00 8.00 4.00 7.00

Table 4.1.6.2. Frequency distribution for number of cobs per plant at non-irradiation

conditions (Control).

78


Frequency

Cumulative

Percentage

1 84 97.7 84 97.7

2 2 2.3 86 100.0

Total 86 100.0

Table 4.1.6.3. Frequency distribution for number of cobs per plant at 20 Gray (Gamma

Radiation).


Frequency

Cumulative

Percent

1 43 64.2 43 64.2

2 17 25.4 60 89.6

3 5 7.5 65 97.0

4 1 1.5 66 98.5

6 1 1.5 67 100.0

Total 67 100.0


Radiation).

79


Frequency

Cumulative

Percent

1 21 55.3 21 55.3

2 11 28.9 32 84.2

3 3 7.9 35 92.1

6 1 2.6 36 94.7

7 1 2.6 37 97.4

8 1 2.6 38 100.0

Total 38 100.0


Radiation).


Frequency

Cumulative

Percentage

1 3 42.9 3 42.9

2 1 14.3 4 57.1

3 1 14.3 5 71.4

4 2 28.6 7 100.0

Total 7 100.0


Radiation).

80


Frequency

Cumulative

Percentage

0 1 2.0 1 2.0

1 25 49.0 26 51.0

2 12 23.5 38 74.5

3 4 7.8 42 82.4

4 7 13.7 49 96.1

5 1 2.0 50 98.0

7 1 2.0 51 100.0

Total 51 100.0

Figure 4.1.6.1. Histogram for number of cobs per plant at non-irradiation condition

(Control).

81

Figure 4.1.6.2. Histogram for number of cobs per plant at 20 Gray (Gamma Radiation).


82



83

4.1.7. Diameter of the cobs:

Summary statistics for diameter of the cobs showed variation between the

treatments of different gamma irradiations. Mean value for diameter of the cobs was

35.09 in normal conditions, 24.15 at the mutagenic dose of 20 gray, 23.68 at 40 gray, 20.86

at 60 gray and 28.61 at 80 gray gamma radiations. Maximum diameter of cobs was observed

in normal conditions and minimum value of cob diameter was observed 20.86 at 60 gray

(Table 4.1.7.1). It showed that different doses of radiation brought changes in genetic

material which effect randomly. Diameter of the cobs is an important morphological trait

which helps us to estimate the total production of the maize crop.

Coefficient of variation was 18.33 for in normal condition, 47.62 at 20 gray, 47.31

at 40 gray, 57.96 at 60 gray and 32.93 at 80 gray. According to the frequency distribution

value, it was ranged from 22 to 48 in normal condition. Histogram curve also showed that

2 cobs had 22 mm diameter but 6 cobs had 25 mm diameter, 6 cobs had 26 mm diameter,

4 cobs had 27 mm diameter, 2 cobs had 28 mm diameter, 4 cobs had 30 mm diameter and

2 cobs had 31 mm diameter (Table 4.1.7.2), also explained in Figure 4.1.7.1. Diameter of

cob showed 4 to 44 values due to gamma radiation which brought genetic changes in genetic

material at the dose of 20 gray (Table 4.1.7.3). Histogram curve showed that cob diameter

varied from 1 mm to 44 mm, 1 cob had 1.9 mm diameter, 5 cobs had 5 mm diameter, 11

cobs had 28 mm diameter and 3 cobs had 44 mm diameter. In this experiment, it was found

that most of the cobs had 29 mm diameter on an average (Figure 4.1.7.2). Table 4.1.7.4,

frequency distribution value ranged from 6 to 40 at the dose of 40 gray. Figure 4.1.7.3

showed that diameter of the cobs vary from 6 mm to 40

mm at 40 gray due to mutagenic effects. It was elaborated that 4 cobs had 8 mm

diameter, 6 cobs had 17 mm diameter, 9 cobs had 37 mm diameter and 2 cobs had 41 mm

diameter. At the dose of 40 gray, lot of variation was observed with in one trait. Frequency

distribution for the diameter of the cobs at 60 gray showed frequency values ranged from 7

to 34 as in Table 4.1.7.5. Histogram curve for diameter of the cobs at 60 gray showed that

1 cob had 7 mm diameter, 1 cob had 9 mm diameter, 1 cob had 13 mm diameter, 1 cob had

17 mm diameter and 2 cobs had 33 mm diameter and 1 cob had 34 mm diameter (Figure

4.1.7.4). Frequency distribution value for diameter of the cobs ranged from 6 mm to 43 mm

in diameter at 80 gray as in Table 4.1.7.6. It is also presented in histogram curve in Figure

84

4.1.7.5. Though 80 gray was used to induce mutation but it was found that most of the cobs

had more than 13 mm diameter and some cobs had more than 40 mm diameter (Figure

4.1.7.5). In present study, it was observed that mutation did not play a positive role to

increase the diameter of the cob as compare to the normal. But in most of the cases cob‟s

diameter was reduced due to the negative effect of mutation. As Ali et al. (2014) concluded

that with all other yield and yield components; diameter of the cob is very effective tool to

improve the grain yield and fodder yield per plant at maturity stage. Although mutation did

not induce mutation positively to increase the diameter of the cob but it played a key role

to increase the cob length as explained in sub-heading 4.1.5.

Table 4.1.7.1. Summary statistics for diameter of cobs under different treatments.


Low 95% CI 33.11 21.34 20.00 9.68 25.96

Mean 35.09 24.15 23.68 20.86 28.61

Up 95% CI 37.10 26.95 27.40 32.04 31.26

SD 6.43 11.50 11.21 12.09 9.42

Variance 41.42 132.22 125.57 146.14 88.76

SE Mean 0.99 1.41 1.82 4.57 1.32

C.V. 18.33 47.62 47.31 57.96 32.93

Minimum 22.00 0.00 6.00 7.00 0.00

Median 36.00 27.00 24.50 17.00 30.00

Maximum 48.00 44.00 40.00 34.00 43.00

Table 4.1.7.2. Frequency distribution for diameter of cob without irradiations (Control).


Frequency

Cumulative

Percentage

22 2 2.3 2 2.3

25 6 7.0 8 9.3

85

26 6 7.0 14 16.3

27 4 4.7 18 20.9

28 2 2.3 20 23.3

30 4 4.7 24 27.9

31 2 2.3 26 30.2

32 2 2.3 28 32.6

34 2 2.3 30 34.9

35 6 7.0 36 41.9

36 10 11.6 46 53.5

37 8 9.3 54 62.8

38 6 7.0 60 69.8

40 6 7.0 66 76.7

41 6 7.0 72 83.7

42 6 7.0 78 90.7

43 2 2.3 80 93.0

44 4 4.7 84 97.7

48 2 2.3 86 100.0

Total 86 100.0

Table 4.1.7.3. Frequency distribution for diameter of cob at 20 Gray (Gamma Radiation).


Frequency

Cumulative

Percentage

4 2 3.0 3 4.5

5 2 3.0 5 7.5

86

6 4 6.0 9 13.4

8 1 1.5 10 14.9

11 1 1.5 11 16.4

12 1 1.5 12 17.9

14 3 4.5 15 22.4

15 5 7.5 20 29.9

18 2 3.0 22 32.8

19 1 1.5 23 34.3

20 1 1.5 24 35.8

22 2 3.0 26 38.8

23 3 4.5 29 43.3

25 1 1.5 30 44.8

26 3 4.5 33 49.3

27 4 6.0 37 55.2

28 6 9.0 43 64.2

29 1 1.5 44 65.7

30 1 1.5 45 67.2

31 1 1.5 46 68.7

32 2 3.0 48 71.6

33 3 4.5 51 76.1

Continue

34 3 4.5 54 80.6

35 2 3.0 56 83.6

36 1 1.5 57 85.1

87

37 2 3.0 59 88.1

38 2 3.0 61 91.0

39 1 1.5 62 92.5

40 1 1.5 63 94.0

41 1 1.5 64 95.5

42 1 1.5 65 97.0

44 2 3.0 67 100.0

Total 67 100.0



Frequency

Cumulative

Percentage

6 1 2.6 1 2.6

7 1 2.6 2 5.3

8 2 5.3 4 10.5

9 2 5.3 6 15.8

10 1 2.6 7 18.4

14 1 2.6 8 21.1

15 5 13.2 13 34.2

17 1 2.6 14 36.8

18 1 2.6 15 39.5

19 2 5.3 17 44.7

Continue

20 1 2.6 18 47.4

23 1 2.6 19 50.0

88

26 3 7.9 22 57.9

27 1 2.6 23 60.5

28 2 5.3 25 65.8

30 1 2.6 26 68.4

34 1 2.6 27 71.1

36 2 5.3 29 76.3

37 4 10.5 33 86.8

38 3 7.9 36 94.7

39 1 2.6 37 97.4

40 1 2.6 38 100.0

Total 38 100.0



Frequency

Cumulative

Percentage

7 1 14.3 1 14.3

9 1 14.3 2 28.6

13 1 14.3 3 42.9

17 1 14.3 4 57.1

33 2 28.6 6 85.7

34 1 14.3 7 100.0

Total 7 100.0

Table 4.1.7.6. Frequency distribution for diameter of cobs at 80 Gray (Gamma Radiation).

89


Frequency

Cumulative

Percentage

6 1 2.0 2 3.9

7 1 2.0 3 5.9

16 2 3.9 5 9.8

18 2 3.9 7 13.7

20 2 3.9 9 17.6

21 1 2.0 10 19.6

23 1 2.0 11 21.6

24 4 7.8 15 29.4

25 3 5.9 18 35.3

26 3 5.9 21 41.2

27 2 3.9 23 45.1

29 1 2.0 24 47.1

30 2 3.9 26 51.0

31 3 5.9 29 56.9

32 1 2.0 30 58.8

33 3 5.9 33 64.7

34 3 5.9 36 70.6

35 3 5.9 39 76.5

36 1 2.0 40 78.4

37 2 3.9 42 82.4

38 2 3.9 44 86.3

39 2 3.9 46 90.2

Continue

90

40 1 2.0 47 92.2

41 2 3.9 49 96.1

42 1 2.0 50 98.0

43 1 2.0 51 100.0

Total 51 100.0

Figure 4.1.7.1. Histogram for diameter of cobs at non-irradiation condition (Control).

91

Figure 4.1.7.2. Histogram for diameter of cobs at 20 Gray (Gamma Radiation).


92



93

4.1.8. Number of grains per row:

Summary statistics for number of grains per row showed variation between

treatments of different gamma irradiations. Mean value for number of grains per row was

19.86 in normal conditions, 6.57 at 20 gray, 6.60 at 40 gray, 7.57 at 60 gray and 6.84 at 80

gray gamma radiations. Maximum number of grains per row was observed in normal

conditions and minimum value for number of grains per row 0 was observed at in all doses

as in Table 4.1.8.1; because in most of the cases unfertile cob was developed. It was found

that unfertile ovaries were present and there was blatant separation between rows of ovaries

without grain. This showed that different doses of radiation brought changes in genetic

material which brought changes randomly. Number of grains per row is an important

morphological trait which helps us to estimate the total production of maize crop.

Coefficient of variation was 53.09 for in normal condition, 133.07 at 20 gray, 121.30

at 40 gray, 134.01 at 60 gray and 87.75 at 80 gray. According the frequency distribution

value, number of grains per row was ranged from 4 to 42 in normal conditions (Table

4.1.8.2). It showed lot of variation with in a trait as elaborated in Figure 4.1.8.1; 4 cobs had

4 number of grains per row, 4 cobs had 5 number of grains per row, 2 cobs had 6 number

of grains per row, 2 cobs had 8 number of grains per row, 8 cobs had 9 number of grains

per row, 2 cobs had 10 number of grains per row, 4 cobs had 11

number of grains per row, 2 cobs had 12 number of grains per row, 6 cobs had 14

number of grains per row, 2 cobs had 15 number of grains per row, 2 cobs had 16 number


per row, 4 cobs had 21 number of grains per row, 2 cobs had 22 number of grains per row,

2 cobs had 24 number of grains per row, 2 cobs had 25 number of grains per row, 2 cobs

had 26 number of grains per row, 4 cobs had 28 number of grains per row, 4 cobs had 29

number of grains per row, 2 cobs had 31 number of grains per row, 4 cobs had 32 number


per row, 2 cobs had 37 number of grains per row and 2 cobs had 42 number of grains per

row. Number of grains per row showed 0 to 39 values due to gamma radiation which

brought genetic changes in genetic material at the dose of 20 gray (Table 4.1.8.3). In Figure

4.1.8.2, histogram curve showed that most of grain rows did not have a single grain, but it

was observed that 30 different rows had only 1 grain, 3 rows had 6 grains, 7 rows had 11

grains, 4 rows had 15 grains, 3 rows had 21 grains, 4 rows had 25 grains, 1 rows had 33

94

grains and 1 row had 39 grains. In Table 4.1.8.4, frequency distribution value ranged from

0 to 27 at the dose of 40 gray. As in Figure 4.1.8.3 showed that number of grains per row

vary from 0 to 40 number of grains per row at 40 gray due to mutagenic changes in the

genetic material of plants. Frequency distribution for number of grains per row at 60 gray

showed frequency values ranged from 0 to 28 (Table 4.1.8.5). Histogram curve for the

number of grains per row at 60 gray showed that 2 cobs had 0 number of grains per row, 1

cob had 1 number of grain per row, 1 cob had 4 number of grains per row, 1 cob had 7

number of grains per row and 1 cobs had 13 number of grains per row and 1 cob had 28

number of grains per row explained (Figure 4.1.8.4). Frequency distribution value for

number of grains per row ranged from 0 to 22 number of grains per row at 80 gray (Table

4.1.8.6). The overall trend is also explained in histogram curve in Figure 4.1.8.5. Yousufzai

et al. (2009) and Wali et al. (2010) observed significant interaction between grains per row

and grain yield per plant. But in present scenario, it can be concluded that mutation did not

induce mutation positively especially in case of number of grains per row because number

of grains per row was reduced to a significant extent as compare to the normal treatment.

The present trend can be elaborated blatantly; polygenic mutation occurred at random and

did not follow any particular pattern, this phenomena was also reported by Brock, (1965)

and Astveit, (1967).

Table

95

4.1.8.1. Summary statistics for number of grains per row of maize under different

treatments.


Lo 95% CI 16.62 4.43 4.00 -1.8126 5.15

Mean 19.86 6.57 6.60 7.57 6.84

Up 95% CI 23.10 8.73 9.24 16.95 8.53

SD 10.53 8.72 8.02 10.15 6.01

Variance 110.84 76.37 64.19 102.95 36.05

SE Mean 1.61 1.07 1.30 3.84 0.85

C.V. 53.09 133.07 121.30 134.01 87.75

Minimum 4.00 0.00 0.00 0.00 0.00

Median 21.00 3.00 2.50 4.00 5.00

Maximum 42.00 39.00 27.00 28.00 22.00

Table 4.1.8.2. Frequency distribution for number of grains per row without irradiation

(Control).


Frequency

Cumulative

Percentage

4 4 4.7 4 4.7

5 4 4.7 8 9.3

6 2 2.3 10 11.6

8 2 2.3 12 14.0

9 8 9.3 20 23.3

10 2 2.3 22 25.6

11 4 4.7 26 30.2

12 2 2.3 28 32.6

Continue

96

14 6 7.0 34 39.5

15 2 2.3 36 41.9

16 2 2.3 38 44.2

18 2 2.3 40 46.5

19 2 2.3 42 48.8

21 4 4.7 46 53.5

22 4 4.7 50 58.1

23 4 4.7 54 62.8

24 2 2.3 56 65.1

25 2 2.3 58 67.4

26 2 2.3 60 69.8

28 4 4.7 64 74.4

29 4 4.7 68 79.1

31 2 2.3 70 81.4

32 4 4.7 74 86.0

34 6 7.0 80 93.0

35 2 2.3 82 95.3

37 2 2.3 84 97.7

42 2 2.3 86 100.0

Total 86 100.0

4.1.8.3. row at 2

Radiation).

Table Frequency distribution for number of grains per 0 Gray (Gamma

97


Frequency

Cumulative

Percentage

0 23 34.3 23 34.3

1 7 10.4 30 44.8

2 1 1.5 31 46.3

3 3 4.5 34 50.7

4 2 3.0 36 53.7

5 4 6.0 40 59.7

6 5 7.5 45 67.2

8 1 1.5 46 68.7

9 2 3.0 48 71.6

10 4 6.0 52 77.6

11 2 3.0 54 80.6

13 2 3.0 56 83.6

14 1 1.5 57 85.1

15 1 1.5 58 86.6

16 2 3.0 60 89.6

18 1 1.5 61 91.0

21 1 1.5 62 92.5

24 1 1.5 63 94.0

25 1 1.5 64 95.5

27 1 1.5 65 97.0

35 1 1.5 66 98.5

39 1 1.5 67 100.0

Total 67 100.0


98

4.1.8.4. row at 4

Radiation).


Frequency

Cumulative

Percentage

0 13 34.2 13 34.2

1 5 13.2 18 47.4

2 1 2.6 19 50.0

3 1 2.6 20 52.6

4 1 2.6 21 55.3

5 1 2.6 22 57.9

6 2 5.3 24 63.2

10 3 7.9 27 71.1

12 1 2.6 28 73.7

13 3 7.9 31 81.6

14 2 5.3 33 86.8

16 1 2.6 34 89.5

19 1 2.6 35 92.1

22 1 2.6 36 94.7

27 2 5.3 38 100.0

Total 38 100.0

4.1.8.5. row at 6

Radiation).


Frequency

Cumulative

Percentage


99

0 2 28.6 2 28.6

1 1 14.3 3 42.9

4 1 14.3 4 57.1

7 1 14.3 5 71.4

13 1 14.3 6 85.7

28 1 14.3 7 100.0

Total 7 100.0

Table Frequency distribution for 0 Gray (Gamma

100

4.1.8.6. number of grains per row at 8

Radiation).


Frequency

Cumulative

Percentage

0 7 13.7 7 13.7

1 6 11.8 13 25.5

2 4 7.8 17 33.3

3 4 7.8 21 41.2

5 6 11.8 27 52.9

6 3 5.9 30 58.8

7 2 3.9 32 62.7

8 1 2.0 33 64.7

9 1 2.0 34 66.7

11 2 3.9 36 70.6

12 3 5.9 39 76.5

13 3 5.9 42 82.4

14 2 3.9 44 86.3

15 2 3.9 46 90.2

16 2 3.9 48 94.1

17 1 2.0 49 96.1

18 1 2.0 50 98.0

22 1 2.0 51 100.0

Total 51 100.0


101

102

Figure 4.1.8.1. Histogram for number of grains per row at non-irradiation conditions

(Control).

Figure 4.1.8.2. Histogram for number of grains per row at 20 Gray (Gamma Radiation).

103



104


4.1.9. Number of grains per cob:

Summary statistics for number of grains per cob showed variation between the

treatments of different gamma irradiations. Mean value for number of grains per cob was

288.53 in normal conditions, 89.89 at 20 gray, 88.52 at 40 gray, 94.00 at 60 gray and 88.22

105

at 80 gray gamma radiations. Maximum number of grains per cob was observed 673 in

normal conditions and minimum value for number of grains per cob was observed 308 at

80 gray (Table 4.1.9.1). This showed that different doses of radiation brought changes in

genetic material which results in changes in randomly. Number of grains per cob is an

important morphological trait which helps us to estimate the total production of the maize

crop.

Coefficient of variation was 60.22 for number of grains per cob in normal condition,

139.35 at 20 gray, 130.68 at 40 gray, 130.27 at 60 gray and 92.80 at 80 gray. According to

frequency distribution value, number of grains per cob was ranged from 30 to 673 in normal

conditions (Table 4.1.9.2). Though normal experiment showed somehow variation but most

of the cobs had 290 to 450 grains and few cobs had 690 grains (Figure 4.1.9.1). Number of

grains per cob showed 0 to 553 values due to gamma radiation which brought genetic

changes in genetic material at the dose of 20 gray (Table 4.1.9.3). Histogram curve showed

that 30 cobs did not have a single grain but 5 cobs had 29 grains, 7 cobs had 79 grains, 2

cobs had 170 grains, 4 cobs had 229 grains, 3 cobs had 330 grains, 3 cobs had 439 grains

and 2 cobs had 560 grains at the dose of 20 gray (Figure 4.1.9.2). In Table 4.1.9.4, frequency

distribution value ranged from 0 to 433 at the dose of 40 gray. Figure 4.1.9.3. showed that

number of grains per cob vary from 0 to 433 number of grains per cob at 40 gray due to

mutational changes in the genetic material of the plants because more than 15 cobs did not

have a single grain but 3 cobs had only 20 grains, 4 cobs had 200 grains each, 2 cobs had

320 grains, 1 cob had 380 grains and 2 cobs had 440 grains. Frequency distribution for

number of grains per cob at the dose of 60 gray showed frequency values ranged from 0 to

341 (Table 4.1.9.5). Histogram curve for number of grains per cob at 60 gray showed that

1 cobs had 0 number of grains per cob, 1 cob had 2 number of grain per cob, 1 cob had 11

number of grains per cob, 1 cob had 54 number of grains per cob and 1 cob had 100 number

of grains per cob, 1 cob had 150 number of grains per cob and 1 cob had 341 number of

grains per cob (Figure 4.1.9.4). Frequency distribution value for the number of grains per

cob ranged from 0 to

308 number of grains per cob at 80 gray (Table 4.1.9.6). The overall pattern is also

explained as total number of grains per cob in histogram curve (Figure 4.1.9.5). Inamullah

et al. (2011) investigated significant correlation between yield and number of grains per

cob due to the effect of fertilizer doses. El-Hosary et al. (1994); Lee et al. (1995); Bolanos

and Edmeades (1996); Flower et al. (1996); Singh and Mishra (1996); Balderrama et al.

106

(1997) and Chapman et al. (1997) found additive type of gene action for number of grains

per cob with some other yield related parameters. Many genes were involved to control one

trait. As above discussed, we can conclude that mutagenic agents induce negative mutation

because number of grains per cob was reduced to a great extent in all doses as compare to

the normal treatment.

Table 4.1.9.1. Summary statistics for number of grains per cob of maize under different

treatments.


Low 95% CI 250.17 59.34 50.50 -19.25 65.21

Mean 288.53 89.89 88.52 94.00 88.22

Up 95% CI 326.90 120.45 126.55 207.25 111.27

SD 175.64 125.27 115.68 122.45 81.88

Variance 30833 15693 13382 14995 6704.90

SE Mean 18.93 15.30 18.77 46.28 11.47

C.V. 60.22 139.35 130.68 130.27 92.80

Minimum 30.00 0.00 0.00 0.00 0.00

Median 277.00 45.00 21.00 54.00 58.00

Maximum 673.00 553.00 433.00 341.00 308.00

Table Fr

107

4.1.9.2. equency distribution for number of grains per cob at normal (Control).


Frequency

Cumulative

Percentage

30 2 2.3 2 2.3

52 2 2.3 4 4.7

63 2 2.3 6 7.0

65 2 2.3 8 9.3

71 2 2.3 10 11.6

72 2 2.3 12 14.0

99 2 2.3 14 16.3

103 2 2.3 16 18.6

120 2 2.3 18 20.9

134 2 2.3 20 23.3

137 2 2.3 22 25.6

146 2 2.3 24 27.9

149 2 2.3 26 30.2

157 2 2.3 28 32.6

158 2 2.3 30 34.9

188 2 2.3 32 37.2

199 2 2.3 34 39.5

219 2 2.3 36 41.9

230 2 2.3 38 44.2

232 2 2.3 40 46.5

240 2 2.3 42 48.8

277 2 2.3 44 51.2

Continue

Table Fr

Continue

108

289 2 2.3 46 53.5

299 2 2.3 48 55.8

312 2 2.3 50 58.1

324 2 2.3 52 60.5

341 2 2.3 54 62.8

349 2 2.3 56 65.1

364 2 2.3 58 67.4

393 2 2.3 60 69.8

398 2 2.3 62 72.1

406 2 2.3 64 74.4

412 2 2.3 66 76.7

421 2 2.3 68 79.1

446 2 2.3 70 81.4

494 2 2.3 72 83.7

512 2 2.3 74 86.0

523 2 2.3 76 88.4

549 2 2.3 78 90.7

552 2 2.3 80 93.0

587 2 2.3 82 95.3

622 2 2.3 84 97.7

673 2 2.3 86 100.0

Total 86 100.0

109

4.1.9.3. equency distribution for number of grains per cob at 20 Gray (Gamma

Radiation).


Frequency

Cumulative

Percentage

0 16 23.9 16 23.9

1 1 1.5 17 25.4

2 1 1.5 18 26.9

4 4 6.0 22 32.8

5 2 3.0 24 35.8

7 1 1.5 25 37.3

8 1 1.5 26 38.8

11 1 1.5 27 40.3

15 1 1.5 28 41.8

17 2 3.0 30 44.8

32 1 1.5 31 46.3

34 1 1.5 32 47.8

44 1 1.5 33 49.3

45 1 1.5 34 50.7

47 1 1.5 35 52.2

51 1 1.5 36 53.7

52 1 1.5 37 55.2

57 1 1.5 38 56.7

62 1 1.5 39 58.2

72 1 1.5 40 59.7

74 1 1.5 41 61.2

76 1 1.5 42 62.7

Table Fr

Continue

110

81 1 1.5 43 64.2

84 1 1.5 44 65.7

86 1 1.5 45 67.2

95 1 1.5 46 68.7

103 1 1.5 47 70.1

105 1 1.5 48 71.6

114 1 1.5 49 73.1

119 1 1.5 50 74.6

122 1 1.5 51 76.1

125 1 1.5 52 77.6

126 1 1.5 53 79.1

131 1 1.5 54 80.6

155 1 1.5 55 82.1

210 1 1.5 56 83.6

216 1 1.5 57 85.1

218 1 1.5 58 86.6

220 1 1.5 59 88.1

240 1 1.5 60 89.6

256 1 1.5 61 91.0

298 1 1.5 62 92.5

301 1 1.5 63 94.0

423 1 1.5 64 95.5

428 1 1.5 65 97.0

464 1 1.5 66 98.5

553 1 1.5 67 100.0

111

Total 67 100.0


Radiation).


Frequency

Cumulative

Percentage

0 9 23.7 9 23.7

1 2 5.3 11 28.9

2 2 5.3 13 34.2

7 2 5.3 15 39.5

8 1 2.6 16 42.1

11 1 2.6 17 44.7

14 1 2.6 18 47.4

15 1 2.6 19 50.0

27 1 2.6 20 52.6

41 1 2.6 21 55.3

49 1 2.6 22 57.9

69 1 2.6 23 60.5

74 1 2.6 24 63.2

92 1 2.6 25 65.8

127 1 2.6 26 68.4

145 1 2.6 27 71.1

149 1 2.6 28 73.7

155 1 2.6 29 76.3

187 1 2.6 30 78.9

189 1 2.6 31 81.6

193 1 2.6 32 84.2

Table Fr

Continue

112

218 1 2.6 33 86.8

223 1 2.6 34 89.5

249 1 2.6 35 92.1

305 1 2.6 36 94.7

371 1 2.6 37 97.4

433 1 2.6 38 100.0

Total 38 100.0

Table 4.1.9.5. Frequency distribution for number of grains per cob at 60 Gray (Gamma

Radiation).


Frequency

Cumulative

Percentage

0 1 14.3 1 14.3

2 1 14.3 2 28.6

11 1 14.3 3 42.9

54 1 14.3 4 57.1

100 1 14.3 5 71.4

150 1 14.3 6 85.7

341 1 14.3 7 100.0

Total 7 100.0


Radiation).


Frequency

Cumulative

Percentage

0 7 13.7 7 13.7

113

8 2 3.9 9 17.6

9 1 2.0 10 19.6

10 2 3.9 12 23.5

15 2 3.9 14 27.5

19 1 2.0 15 29.4

25 1 2.0 16 31.4

26 1 2.0 17 33.3

30 1 2.0 18 35.3

33 1 2.0 19 37.3

34 1 2.0 20 39.2

47 1 2.0 21 41.2

52 1 2.0 22 43.1

54 1 2.0 23 45.1

55 1 2.0 24 47.1

57 1 2.0 25 49.0

58 2 3.9 27 52.9

60 1 2.0 28 54.9

66 1 2.0 29 56.9

86 1 2.0 30 58.8

104 1 2.0 31 60.8

109 1 2.0 32 62.7

117 1 2.0 33 64.7

124 1 2.0 34 66.7

131 1 2.0 35 68.6

138 1 2.0 36 70.6

Table Fr

Continue

114

140 1 2.0 37 72.5

161 1 2.0 38 74.5

165 1 2.0 39 76.5

168 1 2.0 40 78.4

174 1 2.0 41 80.4

180 1 2.0 42 82.4

181 1 2.0 43 84.3

182 1 2.0 44 86.3

185 1 2.0 45 88.2

190 1 2.0 46 90.2

198 1 2.0 47 92.2

224 1 2.0 48 94.1

231 1 2.0 49 96.1

255 1 2.0 50 98.0

308 1 2.0 51 100.0

Total 51 100.0

115

Figure 4.1.9.1. Histogram for number of grains per cob at non-irradiation condition

(Control).

Figure 4.1.9.2. Histogram for number of grains per cob at 20 Gray (Gamma Radiation).

116



117


4.1.10. Grains weight per cob:

Summary statistics for the grains weight per cob showed variation between the

treatments of different gamma irradiations. Mean value for the grains weight per cob was

118

68.23g in normal conditions, 23.19g at 20 gray, 24.76g at 40 gray, 26.43g at 60 gray and

26.45g at 80 gray gamma radiations. Maximum grains weight per cob was observed 160g

at 20 gray and minimum value for grains weight per cob was observed 86g at 60 gray (Table

4.1.10.1). This showed that different doses of radiation brought changes in genetic material

which changes randomly but 20 gray dose induced mutation through which grain weight

was increased as compare to the normal treatment. Grains weight per cob is an important

morphological trait which helps us to estimate the total production of the maize crop.

Coefficient of variation was 68.90g for the grains weight per cob in normal

conditions, 145.95g at the dose of 20 gray, 126.38g at 40 gray, 117.70g at 60 gray and

97.92g at 80 gray. According to the frequency distribution value, grains weight per cob was

ranged from 6g to 154g in normal conditions (Table 4.1.10.2). It showed lot of variation

with in a trait (Figure 4.1.10.1). Grains weight per cob showed 0 to 160g values due to

gamma radiation which brought genetic changes in genetic material at the dose of 20 gray

as in Table 4.1.10.3. Histogram curve showed that few cobs had no grain, 14 cobs had 16g

weight per cob, 4 cobs had 26g, 5 cobs had 34g, 3 cobs had 52g, 3 cobs had 61g, 1 cob had

80g and 1 cob had 161g weight per cob (Figure 4.1.10.2). In Table 4.1.10.4, frequency

distribution value ranged from 0 to 110g at the dose of 40 gray. Figure 4.1.10.3 showed that

18 cobs had 7g weight, 5 cobs had 14g weight, 2 cobs had 22g weight, 1 cob had 38g

weight, 4 cobs had 62g and 71g weight and in the last 3 cobs had 111g weight at the dose

of 40 gray. Frequency distribution for grains weight per cob at 60 gray showed frequency

values ranged from 0 to 86 (Table 4.1.10.5). Histogram curve for the grains weight per cob

at 60 gray showed that 2 cobs had 0g grains weight per cob, 1 cob had 11g, 1 cob had 13g,

1 cob had 29g, 1 cob had 46g and 1cob had 86g grains weight per cob (Figure 4.1.10.4).

Frequency distribution value for the grains weight per cob ranged from 0 to 88g grains

weight per cob at 80 gray (Table 4.1.10.6). It is also presented in histogram curve in Figure

4.1.10.5.

Table 4.1.10.1. Summary statistics for grains weight per cob of maize under different

treatments.


Low 95% CI 58.77 14.94 14.50 -2.21 19.17

119

Mean 68.23 23.19 24.76 26.43 26.45

Up 95% CI 78.71 31.45 35.05 55.07 33.74

SD 46.00 33.85 31.30 30.97 25.90

Variance 2183.1 1146.0 979.48 958.95 670.89

SE Mean 5.17 4.14 5.10 11.70 3.63

C.V. 68.90 145.95 126.38 117.17 97.92

Minimum 6.00 0.00 0.00 0.00 0.00

Median 65.00 12.00 11.00 13.00 17.00

Maximum 154.00 160.00 110.00 86.00 88.00

Table 4.1.10.2. Frequency distribution for grains weight per cob without irradiation

(Control).


Frequency

Cumulative

Percentage

6 2 2.3 2 2.3

11 4 4.7 6 7.0

120

12 2 2.3 8 9.3

13 2 2.3 10 11.6

15 2 2.3 12 14.0

17 2 2.3 14 16.3

19 2 2.3 16 18.6

21 2 2.3 18 20.9

22 2 2.3 20 23.3

23 2 2.3 22 25.6

25 2 2.3 24 27.9

26 2 2.3 26 30.2

28 2 2.3 28 32.6

29 2 2.3 30 34.9

32 2 2.3 32 37.2

41 2 2.3 34 39.5

42 2 2.3 36 41.9

50 2 2.3 38 44.2

56 2 2.3 40 46.5

60 2 2.3 42 48.8

65 2 2.3 44 51.2

74 4 4.7 48 55.8

75 2 2.3 50 58.1

77 2 2.3 52 60.5

Continue

78 2 2.3 54 62.8

91 4 4.7 58 67.4

97 2 2.3 60 69.8

101 4 4.7 64 74.4

121

103 2 2.3 66 76.7

113 2 2.3 68 79.1

117 2 2.3 70 81.4

118 2 2.3 72 83.7

134 2 2.3 74 86.0

137 2 2.3 76 88.4

138 2 2.3 78 90.7

141 2 2.3 80 93.0

142 2 2.3 82 95.3

154 4 4.7 86 100.0

Total 86 100.0

Table 4.1.10.3.Frequency distribution for grains weight per cob at 20 Gray (Gamma

Radiation).


Frequency

Cumulative

Percentage

0 17 25.4 17 25.4

1 5 7.5 22 32.8

2 5 7.5 27 40.3

4 2 3.0 29 43.3

8 1 1.5 30 44.8

9 1 1.5 31 46.3

Continue

10 2 3.0 33 49.3

12 1 1.5 34 50.7

13 2 3.0 36 53.7

15 4 6.0 40 59.7

122

16 3 4.5 43 64.2

17 1 1.5 44 65.7

21 1 1.5 45 67.2

22 1 1.5 46 68.7

23 1 1.5 47 70.1

26 1 1.5 48 71.6

29 2 3.0 50 74.6

31 1 1.5 51 76.1

32 1 1.5 52 77.6

34 1 1.5 53 79.1

37 1 1.5 54 80.6

46 2 3.0 56 83.6

50 1 1.5 57 85.1

56 1 1.5 58 86.6

62 1 1.5 59 88.1

64 1 1.5 60 89.6

69 1 1.5 61 91.0

73 1 1.5 62 92.5

81 1 1.5 63 94.0

82 1 1.5 64 95.5

114 1 1.5 65 97.0

144 1 1.5 66 98.5

160 1 1.5 67 100.0

Total 67 100.0

Table 4.1.10.4. Frequency distribution for grains weight per cob at 40 Gray (Gamma

Radiation).


Frequency

Cumulative

Percentage

123

0 11 28.9 11 28.9

1 1 2.6 12 31.6

2 3 7.9 15 39.5

3 2 5.3 17 44.7

4 1 2.6 18 47.4

11 2 5.3 20 52.6

12 1 2.6 21 55.3

13 1 2.6 22 57.9

14 1 2.6 23 60.5

21 1 2.6 24 63.2

22 1 2.6 25 65.8

32 1 2.6 26 68.4

41 1 2.6 27 71.1

46 1 2.6 28 73.7

48 1 2.6 29 76.3

55 1 2.6 30 78.9

56 1 2.6 31 81.6

60 1 2.6 32 84.2

61 1 2.6 33 86.8

66 1 2.6 34 89.5

70 1 2.6 35 92.1

71 1 2.6 36 94.7

Continue

104 1 2.6 37 97.4

110 1 2.6 38 100.0

124

Total 38 100.0


Radiation).


Frequency

Cumulative

Percentage

0 2 28.6 2 28.6

11 1 14.3 3 42.9

13 1 14.3 4 57.1

29 1 14.3 5 71.4

46 1 14.3 6 85.7

86 1 14.3 7 100.0

Total 7 100.0


Radiation)


Frequency

Cumulative

Percentage

0 7 13.7 7 13.7

125

1 1 2.0 8 15.7

2 3 5.9 11 21.6

3 2 3.9 13 25.5

4 2 3.9 15 29.4

5 2 3.9 17 33.3

7 1 2.0 18 35.3

8 1 2.0 19 37.3

9 1 2.0 20 39.2

11 1 2.0 21 41.2

12 2 3.9 23 45.1

15 1 2.0 24 47.1

17 3 5.9 27 52.9

19 1 2.0 28 54.9

22 1 2.0 29 56.9

25 1 2.0 30 58.8

30 1 2.0 31 60.8

34 1 2.0 32 62.7

35 1 2.0 33 64.7

39 1 2.0 34 66.7

40 2 3.9 36 70.6

41 1 2.0 37 72.5

Continue

42 1 2.0 38 74.5

47 1 2.0 39 76.5

48 1 2.0 40 78.4

126

50 1 2.0 41 80.4

51 1 2.0 42 82.4

54 1 2.0 43 84.3

60 1 2.0 44 86.3

67 2 3.9 46 90.2

69 1 2.0 47 92.2

72 1 2.0 48 94.1

76 1 2.0 49 96.1

77 1 2.0 50 98.0

88 1 2.0 51 100.0

Total 51 100.0

127

Figure 4.1.10.1. Histogram for grains weight per cob at non-irradiation condition (Control).

Figure 4.1.10.2. Histogram for grains weight per cob at 20 Gray (Gamma Radiation).

128



129


4.1.11. 100 Grain weight:

Summary statistics for 100 grain weight showed variation between the treatments

of different gamma irradiations. Mean value for 100 grain weight was 22.65g in normal

130

conditions, 17.67g at 20 gray, 17.40g at 40 gray, 15.86g at 60 gray and 22.14g at 80 gray

gamma irradiations. Maximum 100 grain weight was observed 40g at 20 gray and minimum

value for 100 grain weight was observed 28g at 60 gray as in Table 4.1.11.1. This showed

that different doses of radiation brought changes in genetic material which changes

randomly. 100 Grain weight is an important morphological trait which helps us to estimate

the total production of the maize crop.

Coefficient of variation was 29.11g for the 100 grain weight in normal conditions,

65.75g at 20 gray, 67.17g at 40 gray, 75.27g at 60 gray and 50.19g at 80 gray. According

to the frequency distribution value, 100 grain weight was ranged from 12 to 39 g in normal

conditions (Table 4.1.11.2). It showed lot of variation with in a trait which is also explained

in Figure 4.1.11.1. 100 grain weight showed 8 to 40g values due to gamma irradiation which

brought genetic changes in genetic material at the dose of 20 gray (Table 4.1.11.3).

Histogram curve showed that 16 plants had 2g 100 grain weight, 2 plants had 7g, 4 plants

had 13g, 5 plants had 16g, 8 plants had 19g, 10 plants had 22g, 9

plants had 25g, 4 plants had 28g, 6 plants had 31g, 3 plants had 34g, 1 plant had 38g

and 1 plant had 41 g 100 grain weight (Figure 4.1.11.2). In Table 4.1.11.4, frequency

distribution value ranged from 2 to 35g at the dose of 40 gray. Maximum 100 grain weight

35 g was observed and minimum 100 grain weight 2 g was observed. Figure 4.1.11.3

showed that 8 plants had 2g 100 grain weight, 2 plants had 7g, 4 plants had 10g, 1 pant had

13g, 4 plant had 16g, 3 plant had 20g, 2 plant had 22g, 6 plant had 25g, 3 plant had 28g, 2

plants had 31g and 4 plants had 35g 100 grains weight at the dose of 40 gray. Frequency

distribution for 100 grains weight at 60 gray showed frequency values ranged from 13 to

28g (Table 4.1.11.5). Histogram curve for 100 grains weight at 60 gray showed that 2 cobs

had 0 grains on the cob. 1 plant had 100 grain weight 13g, 1 plant had 100 grain weight

19g, 1 plant had 100 grain weight 25g, 1 plant had 100 grain weight 26g and 1 plant had

100 grain weight 26g (Figure 4.1.11.4). Frequency distribution value for 100 grains weight

ranged from 14 to 42g 100 grains weight at 80 gray (Table 4.1.11.6). It is also presented in

histogram curve in Figure 4.1.11.5. Sedhom (1994); Elhosary et al. (1994); Lee et al.

(1995); Bolanos and Edmeades (1996); Flower et al. (1996); Singh and Mishra (1996);

Balderrama et al. (1997) and Chapman et al. (1997) found additive gene action was more

dominant over the dominance gene action for 100-seed weight, grain rows per cob and

grains per cob. SCA effects were significant for grain rows per cob, 100-seed weight and

grain yield per plant. As above discussed, many genes were involved to control one trait.

131

In Present study, it was found that mutation played important role to enhance 100 grain

weight at mutagenic dose of 20 and 80 gray. No doubt, the induced mutation enhance only

1 g at 20 gray and 3 g at 80 gray as compared to non-irradiation treatment. But it created a

hope to enhance production and to carry out further breeding program.

Table 4.1.11.1. Summary statistics for 100 grains weight of maize under different

treatments.


Low 95% CI 21.61 14.84 13.60 4.82 19.01

Mean 22.65 17.67 17.40 15.86 22.14

Up 95% CI 24.69 20.51 21.24 26.89 25.26

SD 6.64 11.62 11.68 11.92 11.11

Variance 43.994 135.01 136.52 142.48 123.44

SE Mean 0.71 1.42 1.89 4.51 1.56

C.V. 29.11 65.75 67.17 75.27 50.19

Minimum 12.00 0.00 0.00 0.00 0.00

Median 22.00 20.00 19.50 19.00 25.00

Maximum 39.00 40.00 35.00 28.00 42.00

Table 4.1.11.2. Frequency distribution for 100 grains weight without irradiation (Control).


Frequency

Cumulative

Percentage

12 2 2.3 2 2.3

132

14 4 4.7 6 7.0

15 4 4.7 10 11.6

16 14 16.3 24 27.9

17 2 2.3 26 30.2

18 6 7.0 32 37.2

19 2 2.3 34 39.5

20 4 4.7 38 44.2

21 2 2.3 40 46.5

22 4 4.7 44 51.2

23 4 4.7 48 55.8

24 2 2.3 50 58.1

25 4 4.7 54 62.8

26 4 4.7 58 67.4

27 4 4.7 62 72.1

28 8 9.3 70 81.4

29 6 7.0 76 88.4

32 2 2.3 78 90.7

33 4 4.7 82 95.3

35 2 2.3 84 97.7

39 2 2.3 86 100.0

Total 86 100.0

Table 4.1.11.3. Frequency distribution for 100 grains weight at 20 Gray (Gamma

Radiation).


Frequency

Cumulative

Percentage

8 1 1.5 17 25.4

133

12 1 1.5 18 26.9

13 3 4.5 21 31.3

15 2 3.0 23 34.3

16 1 1.5 24 35.8

17 2 3.0 26 38.8

18 4 6.0 30 44.8

19 1 1.5 31 46.3

20 3 4.5 34 50.7

21 1 1.5 35 52.2

22 5 7.5 40 59.7

23 4 6.0 44 65.7

24 2 3.0 46 68.7

25 2 3.0 48 71.6

26 5 7.5 53 79.1

27 2 3.0 55 82.1

28 1 1.5 56 83.6

29 1 1.5 57 85.1

30 3 4.5 60 89.6

31 2 3.0 62 92.5

33 1 1.5 63 94.0

34 1 1.5 64 95.5

Continue

35 1 1.5 65 97.0

38 1 1.5 66 98.5

40 1 1.5 67 100.0

134

Total 67 100.0

135

Table 4.1.11.4. Frequency distribution for 100 grains weight at 40 Gray (Gamma Radiation)


Frequency

Cumulative

Percentage

2 1 2.6 8 21.1

6 1 2.6 9 23.7

9 1 2.6 10 26.3

10 2 5.3 12 31.6

11 1 2.6 13 34.2

13 1 2.6 14 36.8

15 2 5.3 16 42.1

16 1 2.6 17 44.7

17 1 2.6 18 47.4

19 1 2.6 19 50.0

20 2 5.3 21 55.3

21 1 2.6 22 57.9

22 1 2.6 23 60.5

24 3 7.9 26 68.4

25 1 2.6 27 71.1

26 2 5.3 29 76.3

28 1 2.6 30 78.9

29 2 5.3 32 84.2

30 1 2.6 33 86.8

32 1 2.6 34 89.5

34 2 5.3 36 94.7

35 2 5.3 38 100.0

Total 38 100.0

136

Table 4.1.11.5.Frequency distribution for 100 grains weight at 60 Gray (Gamma Radiation)


Frequency

Cumulative

Percentage

0 2 28.6 2 28.6

13 1 14.3 3 42.9

19 1 14.3 4 57.1

25 1 14.3 5 71.4

26 1 14.3 6 85.7

28 1 14.3 7 100.0

Total 7 100.0

Table 4.1.11.6. Frequency distribution for 100 grains weight at 80 Gray (Gamma Radiation)


Frequency

Cumulative

Percentage

0 7 13.7 7 13.7

14 2 3.9 9 17.6

15 1 2.0 10 19.6

16 3 5.9 13 25.5

17 5 9.8 18 35.3

18 1 2.0 19 37.3

21 1 2.0 20 39.2

23 2 3.9 22 43.1

24 3 5.9 25 49.0

25 1 2.0 26 51.0

26 2 3.9 28 54.9

Continue

27 5 9.8 33 64.7

137

28 2 3.9 35 68.6

29 1 2.0 36 70.6

30 2 3.9 38 74.5

31 3 5.9 41 80.4

32 2 3.9 43 84.3

33 4 7.8 47 92.2

34 1 2.0 48 94.1

35 1 2.0 49 96.1

39 1 2.0 50 98.0

42 1 2.0 51 100.0

Total 51 100.0

Figure 4.1.11.1. Histogram for 100 grains weight at non-irradiation condition (Control).

138

Figure 4.1.11.2. Histogram for 100 grains weight at 20 Gray (Gamma Radiation).


139



4.1.12. Yield per plant:

Summary statistics for yield per plant showed variation between the treatments of different

gamma irradiations. Mean value for yield per plant was 70.50g in normal conditions, 27.37g

at 20 gray, 26.13g at 40 gray, 34.43g at 60 gray and 29.78g at 80 gray gamma radiations.

140

Maximum yield per plant was observed 194g in normal conditions and minimum value for

yield per plant was observed 86g at 60 gray (Table 4.1.12.1). This showed that different

doses of irradiation brought changes in genetic material which changes randomly. Yield

per plant is an important morphological trait which helps us to estimate the total production

of the maize crop.

Coefficient of variation was 71.79g for the yield per plant in normal conditions, 133.93g at

20 gray, 120.27g at 40 gray, 93.44g at 60 gray and 94.90g at 80 gray. According to

frequency distribution value, yield per plant was ranged from 6 to 194g in normal

conditions (Table 4.1.12.2). It showed lot of variation with in a trait which is also explained

in Figure 4.1.12.1. Yield per plant showed 0 to 160g values due to gamma radiation which

brought genetic changes in genetic material at the dose of 20 gray (Table 4.1.12.3).

Histogram curve showed that 30 plants had 7yield per plant, 8 plants produced 16g, 2 plants

had 25g, 7 plants produced 34g and maximum yield 160g was shown at the dose of 20 gray

(Figure 4.1.12.2). In Table 4.1.12.4, frequency distribution value ranged from 0 to 110g at

the dose of 40 gray. Figure 4.1.12.3 showed that yield per plant vary from 0 to 110 at 40

gray due to mutagenic changes in genetic material of plants. Frequency distribution for

yield per plant at 60 gray showed frequency values ranged from 0 to 86 (Table 4.1.12.5).

Histogram curve for yield per plant at 60 gray showed that 2 plants did not give any yield,

1 plant gave 11g yield, 1 plant gave 43g yield, 1 plant gave 46g, 1 plant gave 55g and 1plant

gave 86g yield (Figure 4.1.12.4). Frequency distribution value for yield per plant ranged

from 0 to 97g yield per plant at 80 gray (Table 4.1.12.6). It is also presented in histogram

curve in Figure 4.1.12.5. Golob and Plestenjak (1999) and Khatum et al. (1999) found a

positive and significant correlation by grain yield per plant with 100-seed weight, number

of grain per cob and cob diameter. (Bruce et al. (2002); Cordova and Burris (2002);

Farshadfar et al. (2002) and Jeanneau et al. (2002) observed additive gene action for some

yield related parameters in general and for grain yield per plant in specific. As earlier

discussed, many gene were involved to control this one trait. But in present studied

scenario, mutagens did not play positive role except to it; Yield per plant were reduced to

great extent in all the mutagenic treatments as compared to non-irradiation treatment.

141

4.1.12.1. Summary statistics for yield per plant of maize under different treatments.


Lo 95% CI 54.92 18.43 15.80 4.67 21.84

Mean 70.50 27.37 26.13 34.43 29.78

Up 95% CI 81.20 36.32 36.46 64.18 37.73

SD 50.60 36.66 31.43 32.17 28.27

Variance 2530.8 1344.1 987.79 1035.0 798.93

SE Mean 5.42 4.48 5.10 12.16 3.96

C.V. 71.79 133.93 120.27 93.44 94.90

Minimum 6.00 0.00 0.00 0.00 0.00

Median 65.00 12.00 11.50 43.00 24.00

Maximum 194.00 160.00 110.00 86.00 97.00

Table 4.1.12.2. Frequency distribution for grains yield per plant at non-irradiation condition

(Control).


Frequency

Cumulative

Percentage

6 2 2.3 2 2.3

11 4 4.7 6 7.0

12 2 2.3 8 9.3

13 2 2.3 10 11.6

15 2 2.3 12 14.0

17 2 2.3 14 16.3

19 2 2.3 16 18.6

21 2 2.3 18 20.9

22 2 2.3 20 23.3

23 2 2.3 22 25.6

Continue

Table

142

25 2 2.3 24 27.9

26 2 2.3 26 30.2

28 2 2.3 28 32.6

29 2 2.3 30 34.9

32 2 2.3 32 37.2

41 2 2.3 34 39.5

42 2 2.3 36 41.9

50 2 2.3 38 44.2

56 2 2.3 40 46.5

60 2 2.3 42 48.8

65 2 2.3 44 51.2

74 4 4.7 48 55.8

75 2 2.3 50 58.1

77 2 2.3 52 60.5

78 2 2.3 54 62.8

91 4 4.7 58 67.4

101 4 4.7 62 72.1

103 2 2.3 64 74.4

113 2 2.3 66 76.7

117 2 2.3 68 79.1

118 2 2.3 70 81.4

134 2 2.3 72 83.7

137 2 2.3 74 86.0

138 2 2.3 76 88.4

141 2 2.3 78 90.7

142 2 2.3 80 93.0

154 4 4.7 84 97.7

194 2 2.3 86 100.0

143

Total 86 100.0

4.1.12.3. Frequency distribution for grains yield per plant at 20 Gray (Gamma

Radiation)


Frequency

Cumulative

Percentage

0 18 26.9 18 26.9

1 3 4.5 21 31.3

2 4 6.0 25 37.3

4 2 3.0 27 40.3

5 1 1.5 28 41.8

8 2 3.0 30 44.8

9 1 1.5 31 46.3

10 2 3.0 33 49.3

12 1 1.5 34 50.7

13 1 1.5 35 52.2

15 2 3.0 37 55.2

16 1 1.5 38 56.7

21 1 1.5 39 58.2

23 1 1.5 40 59.7

29 2 3.0 42 62.7

30 1 1.5 43 64.2

31 3 4.5 46 68.7

32 1 1.5 47 70.1

35 1 1.5 48 71.6

37 1 1.5 49 73.1

40 1 1.5 50 74.6

Table

144

44 1 1.5 51 76.1

Continue

46 2 3.0 53 79.1

47 1 1.5 54 80.6

50 1 1.5 55 82.1

51 1 1.5 56 83.6

56 1 1.5 57 85.1

62 1 1.5 58 86.6

64 1 1.5 59 88.1

69 1 1.5 60 89.6

73 1 1.5 61 91.0

81 1 1.5 62 92.5

82 1 1.5 63 94.0

114 1 1.5 64 95.5

136 1 1.5 65 97.0

144 1 1.5 66 98.5

160 1 1.5 67 100.0

Total 67 100.0

4.1.12.4. Frequency distribution for grains yield per plant at 40 Gray (Gamma

Radiation)


Frequency

Cumulative

Percentage

0 11 28.9 11 28.9

2 1 2.6 12 31.6

3 2 5.3 14 36.8

145

5 1 2.6 15 39.5

7 1 2.6 16 42.1

11 3 7.9 19 50.0

12 2 5.3 21 55.3

13 1 2.6 22 57.9

14 1 2.6 23 60.5

19 1 2.6 24 63.2

22 1 2.6 25 65.8

41 1 2.6 26 68.4

42 1 2.6 27 71.1

48 1 2.6 28 73.7

55 1 2.6 29 76.3

56 1 2.6 30 78.9

60 1 2.6 31 81.6

61 1 2.6 32 84.2

64 1 2.6 33 86.8

66 1 2.6 34 89.5

70 1 2.6 35 92.1

71 1 2.6 36 94.7

104 1 2.6 37 97.4

110 1 2.6 38 100.0

Total 36 100.0

Table 4.1.12.5. Frequency distribution for grains yield per plant at 60 Gray (Gamma

Radiation)


Frequency

Cumulative

Percentage

0 2 28.6 2 28.6

11 1 14.3 3 42.9

Table

146

43 1 14.3 4 57.1

46 1 14.3 5 71.4

55 1 14.3 6 85.7

86 1 14.3 7 100.0

Total 7 100.0

Table 4.1.12.6. Frequency distribution for grains yield per plant at 80 Gray (Gamma

Radiation)


Frequency

Cumulative

Percentage

0 7 13.7 7 13.7

2 1 2.0 8 15.7

3 3 5.9 11 21.6

4 4 7.8 15 29.4

5 1 2.0 16 31.4

9 2 3.9 18 35.3

10 1 2.0 19 37.3

11 2 3.9 21 41.2

12 1 2.0 22 43.1

17 1 2.0 23 45.1

19 1 2.0 24 47.1

Continue

147

22 1 2.0 25 49.0

24 1 2.0 26 51.0

25 1 2.0 27 52.9

30 1 2.0 28 54.9

33 1 2.0 29 56.9

34 2 3.9 31 60.8

35 1 2.0 32 62.7

39 1 2.0 33 64.7

40 2 3.9 35 68.6

41 1 2.0 36 70.6

42 1 2.0 37 72.5

45 1 2.0 38 74.5

48 1 2.0 39 76.5

50 1 2.0 40 78.4

51 1 2.0 41 80.4

56 1 2.0 42 82.4

60 1 2.0 43 84.3

67 2 3.9 45 88.2

69 1 2.0 46 90.2

76 1 2.0 47 92.2

82 1 2.0 48 94.1

88 1 2.0 49 96.1

94 1 2.0 50 98.0

97 1 2.0 51 100.0

148

Total 51 100.0

Figure 4.1.12.1. Histogram for grains yield per plant at non-irradiation condition (Control)

Figure 4.1.12.2. Histogram for grains yield per plant at 20 Gray (Gamma Radiation).

149



150


CHAPTER 5 SUMMARY

Mutagenic agents played important role to induce mutation in the genome of maize

(Zea mays L.). Physical mutagen (gamma rays) was used to induce the mutation; Isotope

of Cobalt (60Co) produced gamma rays which were bombarded on the seeds of maize.

Mutation often showed negative effects on the genetic makeup of the maize that were

observed on different morphological traits during the studied experiment. In present

investigation, it was observed that the mean value for different quantitative traits shifted

151

both in positive and negative orders due to mutagenic treatments. An irregular relationship

was found between the concentrations and effects in the mean performance for certain traits

in present study.

Owing to positive and negative effects of mutation, some traits showed positive response

to mutagenic changes at the specific dose; for example plant height was increased to 192

cm at the dose of 20 gray as compared to plant height at normal condition. Days taken to

silking were reduced to 57 days from 62 days at the dose of 60 gray which showed positive

induction to fulfill the dream of early maturity of the crop. In the same way, days taken to

tasseling reduced to 53 days from 56 days which was also a positive sign to decrease the

harvesting date. There was a little change in reduction of days taken to tasseling, but a little

change would prove a contribution to achieve further breeding objectives. Number of grain

rows increased to 22 rows per cob at dose of 40 gray as compared to the normal treatment.

Cob length increased to 23 cm at the dose 20 gray as compared to cob length of 20 cm in

normal treatment. Number of cobs per plant increased to 8 cobs at the dose of 40 gray as

compared to the 2 cobs per plant at normal condition. Grains weight per cob was improved

to 160g at the dose of 20 gray as compare to the 154g at normal condition. In 100 grain

weight, Only 1 gram increased was observed at the dose of 20 gray as compared to

controlled condition.

On contrary to positive mutation, some traits showed opposite and negative response owing

to physical mutagens. It was observed that number of cobs increased to 8 cobs per plant as

compared with 2 cobs per plant in normal treatments. No doubt number of cobs per plant

increased to 8 cobs/plant but most of the cobs were unfertile and it was impossible to carry

out the induced mutation for further breeding program. Diameter of cob reduced to a great

extent up to 34 mm at dose of 60 gray as compared to the 48 mm at normal condition.

Number of grains per row decreased to 22 grains per row as compared to the 42 grains at

non-irradiation treatment. In the same way, number of grains per cob were decreased to 308

grains at the dose of 80 gray equates with 673 grains in normal condition. In the last but not

the least, decreasing trend was observed in yield per plant; yield was decreased to 86g at

the dose of 60 gray equates with 194g at controlled condition.

In all traits, positive and negative mutation was observed at all mutagenic levels

either 20 gray, 40 gray, 60 gray or 80 gray. As above discussed, number of grain rows per

cob and cob length increased but the grain yield was decreased. It was observed that most

152

of the ovaries were not developed into grain that was why decreasing trend in grain yield

was observed. Many factors can be imagined hypothetically; doses of mutagen influenced

on either ovaries resulting behind unfertile ovaries, unfertile silks or sterile pollens. But it

is concluded that polygenic mutation always occur at random and do not follow any

particular pattern as stated by Brock, (1965) and Astveit, (1967). The positive shift in the

mean values of characters indicates that there was a scope for selection and further

improvement.

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to-rise-by-10pc-igc.html

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