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STUDIES ON THE PATHOGENIC POTENTIAL AND LIFE CYCLE OF ROOT-KNOT
NEMATODES (MELOIDOGYNE SPPJ
INFECTING BEANS
D I S S E R T A T I O N
SUBMITTED IN PARTIAL FUUFJLMENT OF THE REQUIREMENTS
FOR THE AWARD OF THE DEGREE OF
lHaHtcr of piyil00opI|Q IN
BOTANY (PLANT PATHOLOGY)
BY
IRAM TARig AZMI
D E P A R T M E N T O F B O T A N Y A L . I G A R H M U S L I M U N I V E R S I T Y
A L . I C 3 A R H ( I N D I A )
2006
DS3624
vQv>^' X^^'^J'X^AL^c
^^•C H.)^ v • J 'W/'
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dedicated
My TamiCy
Dr. Tabreiz Ahmad Khan M.Sc. Ph.D.(Alig.), F.L.S.(London) F.N.S.I, F.S.P.P.S.. F.N.R.S. Lecturer
Phone (0)0571-2702016 (R) 0571-2701711
(Mob.): 9411413760 E-mail: khantabreiz'S -editTmaii.com
DEPARTMENT OF BOTANY ALIGARH MUSLIM UNIVERSITY ALIGARH - 202002, INDIA
Dated .?:t.:.''.k.:P&
Certificate
This is to certify that the work presented in this dissertation
entitled "Studies on the Pathogenic Potential and Life Cycle of Root-
Knot Nematodes (Meloidogyne spp.) Infecting Beans" is an original
piece of work carried out by Mrs. Iram Tariq Azmi under my guidance
and supervision and has not been submitted elsewhere for the award of
any other degree and can be submitted in partial fulfilment of the
requirements for the award of the degree of Master of Philosophy in
Botany (Plant Pathology).
( Tabreiz Ahmad Khan ) Supervisor
A cknowledgements
I wish to express my debt and gratitude to my respected supervisor
Dr. Tabreiz Ahmad Khan, Lecturer, Department of Botany, Aligarh
Muslim University, Aligarh. Out of his busy schedule he gave me liberty to
encroach upon his valuable time to complete my work. I feel short of
vocabulary to express my heartiest feelings and deepest sense of gratitude
for his keen interest, enthusiastic support, valuable guidance and constant
supervision.
I am greatly beholden to Prof. Ainul Haq Khan, Chairman
Department of Botany, Aligarh Muslim University, Aligarh for providing
the necessary facilities.
For co-operation, support and a good friendly atmosphere, I extend
thanks to my lab colleagues, Mr. Mohd. Shaikhul Ashrafand Miss Shweta
Sharma and seniors Miss Rasheeda Perveen, Miss Sami Kauser and Miss
Kauser Wani.
I have been lucky to have friends like Shafia, Tabussum, Menu and
Iram for their moral support, encouragement and valuable co-operation.
Thanks to my near and dear ones.
In the last I am thankful to my family members. Their interest,
encouragement and support have been indispensable to complete this work,
otherwise it would have not been possible to achieve this goal without their
love and affection.
(IRAM TARIQ AZMI)
CONTENTS
PAGE NO.
Introduction 1-3
Review of literature 4-38
Materials and Methods 39-44
3.1 Preparation and sterilization of soil mixture 3 9
3.2 Raising and maintenance of test plants 39
3.3 Raising and preparation of nematode inoculum 40
3.4 Inoculation techniques 41
3.5 Experiments 41
3.5.1 Pathogenicity of root-knot nematodes 42
3.5.2 Studies on the life cycle of Meloidogyne 42-43
incognita and Meloidogyne javanica on
mung bean and lablab bean.
3.6 Recording of observations 43-44
I Plant growth determination 43
II Root galling estimation 43
III Root nodule estimation 43
rV Nematode population estimation 43
V Statistical analysis 44
Results 45-52
4.1 Studies on the pathogenicity of Meloidogyne 45
javanica on mung bean {Vigna radiata L. var.
Jawahar 45)
4.2 Studies on the pathogenicity of Meloidogyne 45
incognita on mung bean (Vigna radiata L.var.
Jawahar-45)
4.3 Studies on pathogenicity of Meloidogyne javanica 47
on lablab bean (Dolichos lablab var.Glory)
4.4 Studies on the pathogenicity of Meloidogyne 48
incognita on lablab bean (Dolichos lablab var. Glory)
4.5 Studies on the life cycle of Meloidogyne incognita 49
on mung bean (Vigna radiata var. Jawahar 45)
4.6 Studies on the life cycle of Meloidogyne javanica 50
on mung bean {Vigna radiata var.Jawahar 45)
4.7 Studies on the life cycle of Meloidogyne incognita 51
on lablab bean {Dolichos lablab var. Glory)
4.8 Studies on the life cycle of Meloidogyne javanica 52
on lablab bean {Dolichos lablab var. Glory)
Discussion 53-56
5.1 Pathogenicity of root-knot nematode (Me/o/fifogv«e 53-54
spp.) on mung bean and lablab bean
5.2 Life cycle of root-knot nematode {Meloidogyne spp.) 54-56
on mung bean and lablab bean
SUMMARY AND CONCLUSION 57
REFERENCES 58-76
Introduction
CHAPTER-1
INTRODUCTION
Pulse crops occupy an important position in Indian agriculture and
have a special bearing towards the food economy as these constitute the
major sources of protein to the over-whehning large number of vegetarian
population in the country. On an average about 23 million hectares area is
occupied under pulse crops. However, the production of food grain has
been stagnating between 10-12 million tones. Among the different pulse
crops grovm in our country, gram {Cicer arietinum L.) and arhar {Cajanus
cajan L.) are the most important ones followed by pea (Pisum sativum L.),
green gram (Vigna radiata L.), black gram (Phaseolus mungo L.), horse
gram {Dolichos uniflorus Lam.), lentil {Lens culinaris Medik.) and lathyrus
(Lathyrus sativus L.). The legumes like cowpea [Vigna unguiculata (L.)
Walp.], french bean (Phaseolus vulgaris L.) and other beans are also
cultivated in small scale in India.
Plant parasitic nematodes the "unseen enemies" of mankind are
ubiquitous and cause damage to all the agriculturally important crops viz.
cereals, legumes, oilseeds, ornamentals, vegetables, spices and condiments.
The crop losses due to nematodes are not only in the form of reduced plant
growth and yield but are also in the form of marketable quality of the
produce. Plant parasitic nematodes affect the production and economy of
crop in diverse ways such as reduction in quality and quantity of crop, need
of additional fertilizers and water, application of nematicides and
impediment of production and trade by phytosanitary regulations
(Weischer, 1968). Moreover, the amount of damage caused by plant
parasitic nematodes is governed by a number of factors such as the
nematode species, the size of nematode population, susceptibility of the
host plant, environmental factors and presence of other organisms.
There are numerous estimates of the economic importance of
nematodes in crop production on a world-wide and individual on country
basis, but precise values can't be determined. It is because of the
nematode's "small size and hidden way of life" and lack of definite
information on its occurrence and pathogenicity. Sasser and Freckman
(1987) have indicated an annual crop losses due to plant-parasitic
nematodes on the world-wide basis to the tune of $ 100 billion. The average
loss of all crops has also been estimated to be about 10% due to nematodes
(Sasser, 1989). In India some attempts have been made to estimate the
losses due to nematodes in important commercial crops. Annual losses to
the extent of Rs 40 million in wheat and Rs 30 million in barley due to
"molya disease" caused by Heterodera avenae Wollenweber, 1924 are
considered common in Rajasthan alone. The ear-cockle of wheat {Triticum
aestivum L.) caused by Anguina tritici (Steinbuch, 1799) Filipjev, 1936
causes an annual loss of over Rs. 75 million even at low infestation levels
of one percent. Around Rs.20 million worth of loss in coffee {Coffea
arabica L.) due to root-lesion nematode, Pratylenchus coffeae
(Zimmerman, 1898) Filipjev & Stekhoven, 1941 occurs annually. The
losses due to root-knot nematode have been estimated from 25-50%
depending upon the crops cultivated. It has been estimated by Indian
Agricultural Research Institute, New Delhi that about 10 percent of crop
losses is due to the attack of plant-parasitic nematodes. About 100
nematodes diseases are considered for major economic significance in the
world (Sitaramaih and Naidu, 2003).
Plant parasitic nematodes are one of the serious pests of pulse crops
in India and elsewhere in the world. The root-knot nematodes, as the name
suggests cause galling or knots in the roots are considered as the serious
constraints in the pulse production in all pulse growing areas of India.
Studies conducted by various workers have found negative correlations
between the population density of nematode and the crop yield. Srivastava
et al, (1974) reported significant reduction in yields of pulse crops f ue to
Meloidogyne javanica (Treub, 1885) Chitwood, 1949. Upadhyay and
Dwivedi (1987) reported 33 and 40% yield losses of pea and chickpea
{Cicer arietinum L.) respectively to Meloidogyne incognita (Kofoid and
White, 1919) Chitwood, 1949 infection. Yield loss of peas from 19.95-
20.42% due to M. incognita was also estimated by Reddy (1985). Similarly,
Darekar and Jagdale (1989) found 28.35% loss in chickpea yield due to M
incognita. In mung bean (Vigna radiata L.), avoidable losses under field
conditions due to M. javanica ranged from 42.1-93.4% (Gupta and Verma,
1993). The yield loss of 18-65% and 23-49% due to M. incognita and M.
javanica respectively on mung bean has been reported from Uttar Pradesh
(Shanna et al, 2002).
During the survey of plant parasitic nematodes associated with pulse
crops mung bean {Vigna radiata) and lablab bean (Dolichos lablab L.) in
and around Aligarh were observed to be heavily infected with species of
root-knot nematodes viz. M incognita and M. javanica. The association of
root-knot nematodes with these plants showed stunting, yellowing and leaf
margin drying leading to premature death of plants. Keeping in view the
importance of beans (Dolichos lablab and Vigna radiata) and scanty
information available on pathogenicity and life cycle of root-knot
nematodes on beans, the following investigations were carried out:
1. Studies on the pathogenicity of M incognita on mung bean and lablab
bean.
2. Studies on the pathogenicity of M javanica on mung bean and lablab
bean.
3. Studies on the life cycle ofM. incognita on mimg bean and lablab bean.
4. Studies on the life cycle of M javanica on mung bean and lablab bean.
The information acquired from the present study may provide a
baseline for further research to develop appropriate and effective
management tactics.
(Review of Literature
CHAPTER-2
REVIEW OF LITERATURE
The effects of nematode infection are usually harmflil to plants.
Light to moderate numbers of parasites may not cause much injury but great
numbers severely damage or kill their hosts. The degree of damage depends
on interaction of many factors. Under conditions of stress, such as drought,
inadequate nutrition, or attack by other pathogens, nematodes add an
additional stress, and the plant may die. In favourable circumstances a plant
may survive the same intensity of attack that would kill it under less
favourable conditions.
The most striking effect of nematode infection is a general reduction
in growth. In the field, a patch of poorly growing plants in an otherwise
healthy crop is often the first sign of nematode problems. Affected plants
usually wilt earlier than healthy plants. In row crops, such as soybeans
(Glycine max L.) or potatoes (Solarium tuberosum L.) the healthy crop
forms the canopy over the soil, excluding weeds. But nematode-infected
plants fail to form canopy and weeds often grow profiisely in affected areas.
The normal distribution of plant weight between top and roots may
be drastically altered by nematode infection. Changes in growth of
sugarbeet (Beta vulgaris L.) in small field plots containing different
population level of Heterodera schachtii Schmidt, 1871 the beet cyst
nematode. Total plant weight and harvest declined from 3250 g in
uninfested soil to 444 g in soil with high nematode populations. Roots
decline more rapidly than tops. In healthy plants 38% of the total weight
was in tops and 62% in roots. But, severely damaged plants had almost
exactly opposite distribution of weight i.e. tops were 60% of the total and
roots 40%. This shift in top / root ratio also occurs in other infections, but it
is not always in the same direction. Normal patterns of root growth are
modified when large populations of certain nematodes are present. Species
of Trichodorus Cobb, 1913 are known as stubby root nematodes because
the parasites attack emerging root tips. These become stunted and as new
side roots emerge. The resulting root system consists of a mass of short
stubby roots of little use to plant. Heterodera glycines Ichinohe, 1952 the
soybean cyst nematode, disturbs root growth and also interferes with
nodulation by nitrogen fixing bacteria. Meloidogyne spp. and a few other
nematodes cause roots to become galled (Dropkins, 1980).
Sharma and Sethi (1975) reported that the 100 larvae of either
Meloidogyne incognita or Heterodera cajani Koshy, 1967 per 500g of soil
was the marginal threshold level for producing measurable effects on the
growth of cowpea. The host infestation and nematode multiplication were
found to be density dependent in both cases. The final population was
maximum at an initial inoculum level of 100 larvae in both the nematodes
but the rate of multiplication was highest where in 10 larvae were used.
Nath et al. (1979) found that the root and shoot grow th and pod number of
chickpea plants decreased with increasing inoculum density. Flowering was
delayed by 10 to 15 days following inoculation with 100 or more juveniles
of Meloidogyne incognita and at a density of 1, 00,000 nematodes, the
seedlings failed to flower. Mortality of seedlings was 60 % at the highest
inoculum density 1, 00,000 juveniles after 30 days. The pathogenic
threshold level was 100 juveniles / 500 g soil.
Raut and Sethi (1980) studied the pathogenicity of Meloidogyne
incognita on soybean and observed that there was a progressive decrease in
growth of plant as the inoculum level of M incognita increased. Significant
reduction in top growth, root length and bacterial nodulation in comparison
to uninoculated check plants, were observed at an initial level of 1000
larvae or above per kg of soil which was considered as damaging threshold
level. Mishra and Gaur (1981) evaluated the pathogenicity of M. incognita
and Rotylenchulus reniformis Linford and Oliveira, 1940 on moth bean
(Vigna acontifolia Jacq.). They found that both the nematode species were
pathogenic to moth bean and caused significant growth reductions at 100
larvae / plant. They fiirther indicated that growth of plants was negatively
correlated to the level of inoculation of both nematodes. Meloidogyne
incognita causes significant reduction in shoot length at 10,000 level and
fresh weight at 100 level. Rotylenchulus reniformis did not cause any
significant reduction in shoot length but the fresh shoot weight at 100 level
was significantly reduced. The root length was reduced against an increase
in fresh root weight due to galling with M. incognita, while R. reniformis
did not seem to affect root length or weight significantly. The number of
leaves was only marginally reduced by M. incognita but significantly by R.
reniformis. Both the nematodes reproduced well and the rate of
multiplication decreased drastically with increase in the level of inoculation.
These studies indicated that both M. incognita and R. reniformis
independently pathogenic to moth bean and cause insignificant growth
reduction at initial population below one infective individual per g of soil.
Mani and Sethi (1984) determined the pathogenicity of M. incognita on
chickpea cv. Pusa 209, using five inoculum levels, viz. 0.5, 1.0, 2.0, 4.0 and
8.0 larvae per g of soil along with check and associated check. There was a
progressive decrease in plant growth as the inoculum level of nematode
increased. An inoculum of 2 larvae per g soil was found to be damaging
threshold level of M. incognita on chickpea. Rhizobial nodulation was
adversely affected at all the inoculum levels.
Prasad (1985) evaluated the effect of four initial nematode levels (10,
100, 1000 and 10, 000 / plant) of M incognita, on three cultivars viz. PG-1,
M-13 and J-11, of groundnut (Arachis hypogaea L.), suitable uninoculated
and associated checks were also maintained. With increasing inoculum
level, the plant growth was adversely affected in all the three cultivars.
However, in M-13 and PG-1 the reduction was not statistically significant.
In J-11, 2 larvae / g of soil was damaging threshold. Even though J-11
suffered maximum damage, the nematode reproduction on this variety was
limited. Rate of nematode multiplication was maximum in PG-1 at lowest
inoculum level. At highest level of inoculum, the population was just
maintained in two varieties and less than the initial population in J-11.
Pathak et al. (1985) studied the effect of initial inoculum levels of M.
incognita and R. reniformis on pigeon pea and their interrelationship. They
found significant plant growth reduction with an initial inoculum of 100
juveniles / plant / 500 g of either M. incognita or R. reniformis. In
concomitant inoculations, root-knot formation and final population of M.
incognita was suppressed at all levels in the presence ofR. reniformis.
hioculation of M mcogwz7a juveniles @ 10, 100, 1000, 5000 and
10,000 on chickpea cvs. Pusa 209 and 850 showed a direct correlation
between the inoculum level and reduction in plant weight and number of
root galls per plant (Tiyagi and Alam, 1986). The significant reduction in
plant growth characters of chickpea plant viz. root and shoot length, number
of branches and pods as the inoculum level was increased from 500-8000
second stage of M incognita larvae / 1000 cc of soil. Significant reduction
over uninoculated control was found when 500 or more juveniles / 1000 g
soil were inoculated. Maximum reduction was noticed at 8000 inoculum
level (Singh and Kumar, 1986).
Thakar et al. (1986) observed that maximum reduction in shoot
length of lathyrus plants at 10, 000 larvae of Meloidogyne incognita which
was significantly different from all other treatments. Significant reduction
in fresh shoot weight was observed at 1000 and 10,000 larvae, both also
significantly different from each other. Minimum root weight was observed
at 10,000 larvae and it was at par with 1000 larvae. Significant differences
in root-knot indices were also observed in all the treatments in comparison
to both the checks. However, M. incognita indices significantly increased
with increase in the levels of inoculum. Tiyagi and Alam (1988)
investigated relationship of the inoculum of M. incognita with the disease
development in the presence and absence of root-nodule bacterium,
Rhizobium on mung bean. Plants were inoculated @ 10, 100, 1000, 5000
and 10,000 juveniles per plant. A significant reduction in plant weight was
observed at 100 or more nematode per plant in cv. 'K-85rand at 1000 or
more larvae / plant in cv. 'T-44'. Significant reduction in nodulation was
noted in Rhizobium treated plants were inoculated with nematodes. Ahmed
and Hussain (1988) studied the pathogenicity of M javanica at different
inoculum levels viz. 100,1000, 5000 and 10,000 juveniles / pot on chickpea
plants. Significant suppression of flowering was observed at 1000 inoculum
of M incognita. Pod formation was significantly reduced at the lowest level
of inoculum. The rate of nematode multiplication was inversely related to
inoculum level.
The greater suppression in plant growth, pollen fertility and water
absorption capability in pigeon pea was observed in cv. UPAS 120 than in
cv. ICPL 4 following inoculation with either M incognita or R. reniformis.
Meloidogyne incognita showed a greater effect than R. reniformis.
Significant growth suppression was observed when plants were inoculated
with at least 1000 individuals of the nematode species per plant (Tiyagi et
al, 1989).
Bhagwati and Phukan (1991) evaluated the pathogenicity of
Meloidogyne incognita on pea var. Boneville with four inoculum levels viz.
10, 100, 1000 and 10000 larvae of M incognita per plant grown in 500 g of
soil along with check. Significant plant growth reduction was observed at
1000 larvae of M incognita / ^XaxiX 1500 g of soil. The reproductive rate of
nematode was maximum at the lowest inoculum density and minimum at
the highest inoculum density. Pathogenicity tests gave conclusive evidence
of the destructive potential of M. incognita on black gram. An initial
population density of 100 larvae per 0.5 kg of soil at the root region of
black gram caused significant reduction in shoot length and shoot weight
and proved to be pathogenic to the plant. The reproductive rate of nematode
was maximum at the lowest level of inoculum density and minimum at
highest level of inoculum density (Kalita and Phukan, 1993).
Meena and Mishra (1993) studied the pathogenic potential of M.
incognita on soybean cv. Pusa 24 at five levels of nematization i.e. 0, 10,
100, 1000 and 10,000 J2/ pot. A significant reduction in almost all the plant
growth parameters was obtained with increase in the level of nematode
inoculum. Maximum reduction in all the plant growth parameters was
recorded at the inoculation recorded at the inoculation level of 10,000 J2 /
pot which was followed by the level of 1000 J2/ pot. At these levels plant
shows stunting, yellowing, wilting and sickly appearance. The nematode
showed adverse effect on the number of bacterial nodules which was
significantly reduced with increase in the levels of nematode inoculum. The
number of galls on roots, number of J2 in soil and number of different
developmental stages i.e. eggs, J2, J3 and adults of M incognita inside root
tissue were observed to be increasing with increase in the levels of
inoculum, indicating that soybean is a good host for this nematode. Rao and
Krishnappa (1994) studied the occurrence of root-knot nematode (M
incognita) with a variation in population levels among the districts, with a
mean inoculum level of 0.12 larvae per g soil under field conditions. An
inoculum level of 2 larvae / g soil was found as damaging threshold level on
chickpea cv. Annegiri under green house conditions. Increase in the level of
larval inoculation resulted in proportional decrease in plant growth and an
increase in root-knot disease on chickpea.
Samanathan and Sethi (1996) studied the growth of mung bean as
influenced by different initial inoculum of M incognita. Initial inoculum of
0.5 larvae / g soil was minimum damaging threshold of M incognita on cvs.
PS-16 and Pusa Baisakhi of mung bean and the reproduction of nematode
was found to be density dependent with higher rate of niultiplication at
lower inoculum level. Thankmony et al. (1996) showed that with increasing
inoculum of M incognita, there was progressive decrease in all plant
growth characters fi-om 10 to 10,000 larvae per pot. There was a significant
reduction in fresh and dry weight of both shoot and root with the increasing
levels of nematode inoculum. The final nematodes population also
increased gradually with increasing levels of inoculum. But maximum gall
formation per plant was recorded fi-om 1000 level. The multiplication rate
was inversely proportional to the population density. The results indicated
that an initial inoculum level of 10 J2 / 0.5 kg soil caused significant
reduction in growth characteristic of the cover crop, (Pueraria phaseoloides
L.) over uninoculated control over a period of five months. So an initial
population of 20 nematodes / kg scil can cause significant reduction in the
growth parameters of this crop.
Sharma et al. (1999) studied the pathogenicity of root-knot
nematode, M. incognita on groundnut plants at various inoculum level i.e.
0, 10, 100, 1000 and 10,000 nematodes / plant. Generally two highest levels
viz. 1000 and 10, 000 significantly reduced plant growth. However, with
increased in inoculum level, soil population also increased significantly.
Malhotra et al. (1999) studied the pathogenicity and varietal reaction
of black gram against M. incognita and Fusarium oxysporum
Schlechtendahl. They reported the significant growth reduction of black
gram cv. T-9 at an inoculum level of 1000 juvenile of M incognita /kg soil
which was damaging threshold level.
Singh and Goswami (2000) reported that increase in the level of M.
incognita i.e. 10, 100, 1000 and 10000 nematodes / 500 g soil resulted in
proportional decrease in plant vigour and rhizobial nodulation. Root galls
were disturbed all over the root system with few big and irregular galls.
Significant plant growth reduction over control was observed with an initial
population of 1000 nematode / 500 g soil which was established as potential
pathogenic level of M incognita. An increase in total nematode population
in soil was recorded at each inoculum level except 10,000 level where
population had gone down even below the initial populations. A significant
reduction in number of nematode galls and size can be attributed to over all
reduction in the root system. Results show that root-knot infestation had a
pronounced effect on rhizobial nodule formation. The nematode larvae may
be interfering in formation of nodules by competing with the root nodule
bacteria and reduction of nodule size may be due to interaction between
rhizobial and nematode population. The inoculum level of 100 juveniles of
M. incognita per plant caused significant reduction in growth characters of
pulse crops and proved to be pathogenic. Reduction in grov^ characters
varied at different inoculum levels. Maximum decrease was in lathyrus
10
while minimum in french bean at 10,000 level. The multiplication rate of
nematode was maximum at 10 inoculum level and minimum at the highest
level. Gradual reduction in number of bacterial nodules was also observed
with the increase of inoculum levels in all test crops maximum was at
10,000 level (Haider et al, 2003).
Youssef and Nagadi (2004) reported that the inoculation of faba bean
{Vicia faba L.) plants with 0, 10, 100, 1000 and 10,000 larvae of M.
incognita per pot showed significant reduction in plant growth and yield
under the highest inoculum i.e. 10,000 J2 / plant. Haseeb et al. (2005)
reported that damaging threshold level of M. incognita on mung bean was
500 J2 / kg soil. The reproduction factor decreased with the increase in
inoculum level, the highest being at 100 J2/ kg soil and the least at 10,000 J2
/ kg soil.
Singh and Mishra (1974) reported that sugarbeet plants in
uninoculated pots grew well, but those inoculated with higher levels of M.
javanica nematode inoculiun showed unhealthy appearance. Development
of root system of sugarbeet was noted to be significantly reduced in plants
receiving the highest population (5,000) of nematodes per pot. The foliage
of heavily infected plants was observed to have changed morphologically
from its normal structure to lanceolate lamina and longer and upright
petioles. In many cases, yellowing of leaves was associated with nematode
infestation of roots. Inhibition in growth of taproot resulted in the formation
of profuse lateral roots. The plants inoculated with lowest inoculum level
i.e. 10 larvae / pot showed very few root galls. The intensity of gall
formation increased with the increased number of nematodes. The root-knot
index was 4.0 at the highest level of inoculum (5000 larvae per pot).
Average weight of roots (storage tissues) was observed to decline with an
increase in the number of nematodes. It was no surprised that differences in
gross root weight were negligible as the weight of large number of
nematode galls compensated for the loss in weight. Sucrose content in the
11
roots was found to be low under all the treatment as compared to control,
maximum reduction being at the highest inoculum level.
The continuous reduction in length and weight of shoot was recorded
with increase in initial inoculum level. However, significant reduction over
uninoculated control was found only when 100 or more nematode larvae
per 500 g of soil were given. The maximum reduction was observed at
10,000 level. The length of gram root was significantly reduced by
inoculating 100 nematodes. One thousand or more larvae were required to
cause appreciable damage in the root weight. An moculum level of 100
larvae was also sufficient to reduce the number of pods significantly. The
minimum number of pods were obtained at 10,000 level. Maximum number
of galls were formed at 100 level with further increase in the inoculum level
there was corresponding decrease in the formation of galls (Srivastava et
al, 1974). Srivastava et al. (1979) indicated that an inoculum level of 100
larvae of M. javanica per kg of soil significantly reduced the growth of
soybean plant var. Lee. However, number of nodules per plant was reduced
significantly even at lowest level (10 larvae / kg). There was
correspondingly increased reduction in plant growth with an increase in
initial inoculum level. Pod formation was also affected by increasing
inoculum level with significant reduction at 100 larvae / kg of soil.
Dhanger and Gupta (1983) studied the pathogenicity of M javanica
in relation to soil types, size of pots and time interval taking various
observations on growth parameters in chickpea. It was found that an initial
inoculum of 10,000 larvae / plant in smaller pots (15cm) after two months
of inoculations and 1000 and 10,000 larvae /plant in large pots (25cm) after
five months of inoculation proved to be pathogenic in all three types of soil.
Similarly, Rhizobium treated seeds showed better growth characters than
untreated seeds but there was no difference in pathogenic level in both the
treatment (treated and untreated). However, fresh root weight was more in
plants where treatment was done with Rhizobium culture. Gupta et al.
(1987) found that 500 larvae / kg soil of M. javanica significantly reduced
12
the plant growth of black gram. Gupta and Paruthi (1989) studied the
pathogenic relationship of root-knot nematode, Meloidogyne javanica with
broad bean {Viciafaba L.) and reported that 1000 juveniles / plant was the
economic threshold level of M javanica to this crop. In pot experiments,
chickpea seedlings were inoculated with 10, 100, 1000, 4000 or 8000
second stage juveniles of M. incognita per plant. The number of galls per
plants were maximum at the 2000 inoculum level and minimum at 10
inoculum level. An initial inoculum level of 100 juveniles per plant was
sufficient to cause reduction in the plant growth parameters (Bhatti and
Bhatti, 1989).
Patel et al, (1992) indicated that M javanica @ 100 J2 / plant and
above was detrimental to the growth and development of pigeon pea. Total
nematode population / plant significantly increased progressively with an
increase in nematode population fi-om 10 to 10,000 J2/ plant.
In mung bean, an inoculum of 100 second stage juveniles of
Meloidogyne javanica per kg soil was recorded as the damaging threshold
in both Rhizobium treated as well as untreated plants. In cluster bean
(Cyamopsis tetragonoloba L.), a significant decrease in yield was
associated with 10,000 second stage juveniles / kg soil in Rhizobium treated
plants where as 1,000 juveniles decreased the yield, fi-esh shoot weight and
length significantly in imtreated plants over the check (Dalai and Bhatti,
1996).
Patel and Patel (1998) studied the pathogenicity of M. javanica on
groundnut cv. GG20 during Kharif 1996 and 1997 and reported that an
inoculum of 100 J2 and above / plant significantly reduced plant growth
parameters. This reduction progressively increased with an increase in
nematode inoculum level fi-om 10 to 10,000 J2 / plant due to heavy root
galling and profiise egg sac formation on roots. Nematode inoculum level of
10,000 J2 / plant had significantly minimal plant height, fi-esh and dry shoot
weights. Total nematode population increased with an increase in nematode
inoculum levels while nematode reproduction was rate decreased with
13
corresponding increase in inoculum levels and it was maximum at level of
10 J2/ plant and minimum at the highest level.
Idowu (1999) studied the damage potential of root-knot nematodes
(Meloidogyne spp.) on soybean cultivars. He also compared the
pathogenicity of 5 isolates of M arenaria (Neal, 1889) Chitwood, 1949
including 2 host races and a population of M. javanica on soybean cv.
'Kirby' and 'Centennial'. Generally, nematode introduction suppressed the
growth of soybean. Meloidogyne javanica was more pathogenic on soybean
cultivars than M. arenaria. Patel et al. (2001) studied the pathogenicity of
two root-knot nematodes, Meloidogyne incognita and Meloidogyne
javanica on banana {Musa paradisiaca L.) at different inoculum level viz.
100, 1000, 5000, 10000, 50000 and 100000 second stage juveniles per
plant. Significant reduction in plant growth was observed at 500 juveniles /
plant.
Rajendran et al. (1976) reported that there was significant difference
in the plant growth between inoculated and uninoculated Crossandra
undulaefolia S. plants. The inoculated plants exhibited retardation in shoot
growth, with smaller chiorotic leaves almost turning to white in advanced
stages of infestation. Those which received an initial inoculum of M.
incognita of 1000, 2000, 5000 and 10000 nematode larvae were more
seriously affected.
Dhawan and Sethi (1976) reported that there was progressive
decrease in growth of egg plant (Solanum melongena L.) as the inoculum
density oi Meloidogyne incognita increased. Significant reduction in length
of top and root as also in weight of top was observed at an initial inoculum
density of 1000 larvae / 1000 g soil. Maximum nimiber of galls and total
multiplication rate were found at 100 larvae /1000 g soil.
Vaishnav and Sethi (1978) found that a population level of 1000
larvae of M. incognita or adults and larvae of Tylenchorhynchus vulgaris
Upadhyay et a/., 1972 per 500 g of soil was the marginal threshold level for
damaging the plant growth of bajra (Fennisetum typhoides Staf. and
14
Hubbard) in terms of shoot length, shoot weight and root length. The host
infestation in case of root-knot nematode and multiplication in both
nematode species proved bajra to be good host. The effect of combined
inoculum of these nematode species on plant growth was additive.
Tylenchorhynchus vulgaris exhibited antagonistic relationship towards M.
incognita, while T. vulgaris itself reproduced better in the presence of M.
incognita.
Gunasekaran (1979) studied the pathogenicity of the root-knot
nematode, Meloidogyne incognita on patchouli (Pogostemon patchouli
Benth.) imder glasshouse conditions. The experiment was replicated five
times with four treatments viz. 50, 500 and 5000 larval inoculum, and
imtreated control as check. The nematodes, at the higher initial inoculum
level, was found to reduce the height and weight of shoot, the weight of
root, number of branches, number of leaves and number of nodes.
Gaur and Prasad (1980) studied the relationship between the
population density of M. incognita and damage to egg plant has been
investigated .Symptoms were more pronounced of damage with ageing of
the crop, but indicative only at population levels above that initiated
damage. A population density above 1000 second stage juveniles / plant
hastened maturity of the crop resulting in shortened duration of fruiting.
Because of the long duration of the crop, even the low density of 250
juveniles / plant, introduced into rhizosphere, caused significant damage,
which increased to about 80 % yield reduction at 4000 juveniles / plant. The
growth and yield were negatively correlated with the initial as well as final
population. 'Dispersed inoculation' has been considered closer to the field
conditions than the 'localized inoculation' i.e. introducing the nematode
into rhizosphere of established seedlings. The former indicated higher
tolerance level (0.75 to 2.25 juveniles / cm^ of soil) than the latter (0.25 to
0.75 juveniles cm^ of soil).
Kurien and Kuriyan (1981) studied the nature and extent of damage
caused by root-knot nematode, M incognita to brinjal at different inoculum
15
level of 10,100, 500, 1000, 5000 and 10000 larvae per plant. There was
significant reduction in number of leaves, shoot length, in weight of shoot,
in weight of root, in yield and in mean weight of brinjal, by different
inoculum levels of the root-knot nematode, within 108 days of inoculation.
The total nimiber of root-knots present in each plant increased from 148.5 at
the inoculum level of 10 to 412.3 at the inoculum level of 10,000 larvae.
The soil population of M incognita also increased from 28.0 to 243 per 100
ml of soil. It may be inferred that M. incognita is positively involved in the
unthrifty growth of the brinjal plant and consequent reduction in yield.
Rao and Seshadri (1981) conducted eight pathogenicity experiments
viz. four on M incognita and four on R. reniformis. These studies revealed
that 10 days old seedlings of grape {Vitis vinifera L.) were killed by M.
incognita within 30 days of inoculation with an initial population level of
1000 nematodes per pot and above, Vv'hile 1,00,000 larvae of ^. reniformis
were able to kill only three plants out of seven. No death was observed in
seedlings of 60 days and above and also in cuttings of 4 months age.
Inoculations on 60 days old seedlings at 90 days after inoculation showed
more damage by 1000 level of nematodes than 10,000 level in both the
nematodes.
Yadav and Verma (1981) indicated that presence of 10,000 larvae of
M incognita I plant at the time of transplanting is highly pathogenic to
brinjal var. Pusa Purple Long and significantly reduce the plant grov\^ and
increase multiplication of nematode population. Light infestation often and
hundred larvae per plant was found to increase plant growth. The nematode
multiplication rate was higher at such lower larval population.
Reddy (1981) observed significant reductions in plant height and
shoot weight of'purple' variety of passion fnxxX (Passiflora edulis Sims.) at
1000 larvae of M incognita. The plants inoculated with 1000 and 10,000
larvae showed varying degrees of the leaf yellowing and stunting
symptoms. The maximimi root-knot index was observed in treatments
receivmg an inoculum of 10,000 larvae. These results clearly indicate the
16
destructive potential of root-knot nematodes on passion fruit. In case of
yellow variety, (P. edualis var. flavicarpa), there was no significant effect of
different inoculum level on plant growth characters. The root-knot index
was only 2.2 at the maximum inoculum level of 10,000 larvae, suggesting a
tolerant reaction of variety.
Pathogenicity test with M. arenaria gives conclusive evidence of the
destructive potential of this parasite on groundnut on cv. GAUG-10. The
results obtained in this test indicated that significant reduction in plant
growth characters except root weight was observed at inoculum level of
1,000 larvae per kg of soil. Inoculum level can thus be called as minimum
threshold for groundnut. The plants inoculated with 1,000 and 10,000 larvae
showed varying degrees of chlorosis and stunting with reduction in leaf
size. Though an increase on the level of inoculum resulted in increased root
galling as also increased nematode multiplication but this increase was not
proportional indicating there by that the nematode was density dependent.
The highest multiplication rate was observed in treatments receiving an
inoculum at 100 larvae. Considering the potential change the nematode
could cause to groundnut crop, its occurrence in Saurastra area of Gujarat
can be a limiting factor in successful cultivation of this crop unless suitable
control measure are adopted (Dhruj and Vaishnav, 1981).
Significant reduction in Solarium khasianum L. plant height and root
weight was observed in plants receiving the highest (20,000) level of
Meloidogyne incognita. The plants also exhibited severe yellowing and
wilting. Plant growth characters were not significantly affected up to the
level of 2000 larvae per plant (Shetty and Reddy, 1984).
Prasad and Reddy (1984) studied that the pathogenic effects of root-
knot nematode, M. incognita to patchouli were investigated at inoculum
levels of 100, 1000 and 10,000 nematodes per plant under pot culture
conditions. Significant reduction in root and top weights was recorded. As
high as 15.9 and 27.9 % reduction in top & root weights respectively was
recorded, with an initial inoculum level of 10,000 nematodes per plant over
17
a period of six months. Parihar (1985) investigated the effect of initial
inoculum densities of M. incognita on ginger {Zingiber officinalis Rose).
All inoculum densities (1.25, 2.50, 5.00, 10.00 and 20.00) except 0.62
nematodes /g soil, reduced the height and weight of plants over control. At
0.62 level stimulatory effect was recorded. A negative correlation was
observed between lower and higher levels on nematode reproduction.
Acharya (1985) studied the pathogenicity of the root-knot nematode,
M. incognita on betelvine {Piper betel L.) at inoculum levels of 0, 10, 100,
1,000, 10,000 and 30,000 second stage juveniles / 1.5 kg soil. Significant
reduction in length and weight of both shoot and root was noticed at 1000
or more juveniles per pot compared to the plants inoculated with 10
nematodes per pot and uninoculated control. Therefore, inoculimi level of
1000 nemas /.pot./.vine was considered at the minimum pathogenic level of
M. incognita on betelvine.
Jagdale et al. (1985) inoculated betelvine plants with 10, 100, 1000,
10000 and 50000 fi-eshly hatched second stage larvae of M incognita and
found that with an increase in the level of inoculum, there was
corresponding reduction in plant growth. The plants inoculated with 10,000
and 50,000 larvae exhibited significantly low number of leaves with
reduced size. Increased root galling and final nematode population, with
increasing inoculum was not, however proportionate to initial population
density.
The shoot height, the major contributions factor to fiber yield, was
significantly reduced at 1000 larvae per plant in both the jute species viz.
Corchorus capsularis L. and Corchorus olitorius L, when inoculated at 4
day old stage, exhibited significant reduction even at 10 larvae per seedling,
indicating a damaging level of 10 larvae per seedlings at cotyledon stage.
The better ability of C. capsularis jute to withstand nematode injury than C.
olitorius jute is explained by the fact that the former has more extensive
root and shoot system than the latter in seedling stage. Shoot weight, root
length and weight were similarly reduced significantly with an increase in
18
nematode inoculum with maximum at 100 and 1000 nematodes per seedling
at 4"' day and 10"'-14''' day inoculated plants respectively decreasing
thereafter. It is apparent; therefore, that M. javanica is pathogenic to both
the species of jute and the seedlings infested at earlier stages may be affect
as per the density of nematode population. The damaging level of inoculum
per seedling increases with increase in age of the seedling (Mishra and
Singh, 1985).
Sundrababu and Vadivelu (1985) observed that the of root-knot
nematodes, M. incognita and M. javanica has been frequently encountered
with declining crop of tuberose {Polyanthus tuberosa L.), a fragrant and oil
yielding commercially important flower crop in Tamil Nadu. Therefore, the
pathogenicity of three species of Meloidogyne (M incognita, M. javanica,
and M. arenaria) were investigated on tuberose single whorl type. The three
species were introduced in pots containing sprouted tuberose bulbs,
separately at 2 / larvae / g of soil. The results indicated that M. incogpita
and M arenaria were more pathogenic to tuberose than M. javanica. The
'R' ratio of M incognita and M. arenaria was 3.072 and 2.152 respectively
compared to 1.334 in M. javanica. Based on these observations, an
experiment was conducted with logarithmic series of M incognita (0, 10,
100, 1000, and 10,000) on 'single whorl' tuberose. Among the inoculum
levels, 10,000 juveniles / plant reduced the plant grov^. The 'R' ratio was
650.4 at the initial inoculum of 10, 53.28 for 100, 5.28 for 1000 and only
0.43 for 10,000 larvae / plant.
Vaishnav et al. (1985) studied the pathogenic effect of M arenaria
(5000 h I plant). They observed that the healthy plants, were appear green
with well developed leaves as compared to the nematode infested groundnut
plants which were stunted with yellowish leaves and reduced leaf lamina.
Significant reduction in size of leaf lamina and petiole length of infected
plants was also observed. A similar trend was recorded when the plants
were harvested after 60 days. Chlorophyll a, chlorophyll b and total
chlorophyll were also significantly reduced by in comparison to check.
19
Azmi (1986) inoculated seedlings of su-babool (Leucaena
leucocephala L.) with 0, 10, 100, 1000 and 10000 larvae of M incognita
and found that the length and dry weight of shoot and root decreased as the
inoculum density increased. Reduction in growth occurred at 1,000 level
with plants exhibiting stunting, yellowing, browning and defoliation. Severe
galling on roots was also observed.
Sukumaran and Sundraraju (1986) observed that with an increase in
nematode inoculum from 10 to 10000 there was a corresponding decrease
in plant growth of ginger. An initial inoculum level of 10,000 M. incognita
larvae caused significant reduction. The root-knot index also increased with
increase in the inoculum levels. However the multiplication rate was
maximum at 10 nematodes level.
Dhankar et al. (1986) found threshold inoculum level of M
incognita on water melon {Citrullus vulgaris Scharad) as 1000 larvae /kg
soil, at which all the plant growth were reduced significantly over control.
All 10 larvae / kg soil, there was stimulatory effect with extensive root
proliferation. A 10,000 larvae / kg soil, the plants exhibited stunted growth,
yellowing and dropping of leaves and even premature death of plants.
Patnaik and Das (1986) observed significant reductions in the tuber
yield with 100 juveniles of Meloidogyne incognita I pot and maximum
reduction in tuber weight at 1000 juveniles / pot. A nematode inoculum
level of 10 juveniles per pot was sufficient to induce gall formation in
coleus (Coleus parviflorus L.) but at maximum inoculum level of 10,000 J2/
pot
A systemic study was undertaken to find out the pathogenic level of
Meloidogyne javanica on radish (Raphanus sativus L.) and turnip {Brassica
rapa L.), per pot inoculated with different levels of freshly hatched second
stage juveniles of M javanica (i.e.O, 10, 100, 1000, 2000, 5000 and 10,000
J2 / pot). They observed significant reduction in all plant growth
characteristics as compared to uninoculated control at and above level of
2000 h I pot. The reduction was minimum at 10,000 level, but not
20
significantly different at 2000 and 5000 juveniles / plant. The number of
galls / plant was maximum at a level of 1000 J2 / plant. In turnip, galls were
not observed up to 100 J2 / plant. However, a few galls were observed in
radish at this level. No egg masses were observed in radish even at highest
inoculum level; however, some egg masses were observed in turnip at 5000
and 10, 000 J2/ plant (Paruthi et al, 1986).
Mangat and Bhatti (1987) studied the pathogenicity of M. javanica
on Chinese cabbage (Brassica campestris ssp. pekinensis) at different
inoculum levels viz. 0, 10, 100, 1000, 5000 and 10,000 juveniles per plant.
Percentage reductions in shoot length and fresh shoot weight at treatments
of 100 nematodes / 1000 cc soil was 16.52 and 16.90 respectively.
However, percentage in root length at 1000 nematodes / 1000 cc soil was
23.68. In addition, fresh root weight and number of leaves at an inoculum
level of 5000 / 1000 cc soil were reduced by 60.71% and 38.09%
respectively. Gall index was directly proportional with the level of
inoculum.
Acharya and Padhi (1987) reported significant reductions in
betelvine plant growth, particularly shoot and root length, dry weight of
shoot and root at different inoculum levels of Meloidogyne incognita. With
100 or more second stage larvae / 1.5 kg soil expressing minimum
pathogenic level. At this level, symptoms like thinly spread foliage with
small leaves, yellowing and premature shedding of leaves, and also stunting
of plants, were recorded. The shoot and root length were even adversely
affected at 10 larvae. The final nematode population increased significantly
with increase in the level of initial inoculum. These results show that
betelvine is a highly susceptible host of M incognita. Further, at 100 larvae
/1.5 kg soil was recorded as the damage threshold level, the symptoms of
'Champafiilia roga' were also produced.
The yield of Cotton (Gossypium hirsutum L.) significantly reduced at
and above 100 juveniles of M incognita in Desi cotton and at and above
500 juveniles / pot in American cotton. However, qualitative characters
2i
were not affected significantly. Final root-knot index was maximum at and
above 1000 juveniles / plant both in American and Desi cotton. There was
decrease in dry shoot weight and increase in dry root weight with increase
in dry root weight with increase in inoculum level (Rai and Jain, 1987).
The pathogenic effect of M. arenaria and its optimum inoculum
level on tuberose cv. single whorl was assessed in pot culture study under
glasshouse conditions. A logarithmic series 0, 10, 100, 1000 and 10,000 M.
arenaria juveniles per pot were applied after the sprouting of the tuberose
bulbs in 1 litre pots. The results indicated that M. arenaria is a potential
nematode parasite of tuberose affecting plant stand, retarding growth and
reducing flower production. Significant reduction in the plant growth was
observed at 1000 J2 / plant (Sundrababu and Vadivelu, 1987).
Gupta and Yadav (1988) studied pathogenicity of papaya (Carica
papaya L.) by inoculating with 500,1000,2000,4000, 8000 freshly hatched
juveniles of M incognita I plant. The progressive decrease in shoot length,
shoot weight, root length, root weight and reproduction factor were
recorded with increase in level of inoculum. Reductions in shoot length,
root length, and plant weight were found to be significant in the inoculated
plants compared to the uninoculated ones. The number of galls continued to
increase with the increase inoculum levels 4000 to 8000. The tap-root was
suppressed, and lateral roots growth was profuse. The leaves observed to be
distinctly yellowish.
Kaur and Sharma (1988) revealed that all grov^h parameters of
ginger were adversely affected in the presence of M. arenaria. The
nematodes were more pathogenic to root and rhizome formation. The
observation showed that M. arenaria is highly pathogenic to ginger beside
quantitative damage is capable of producing detectable effect on ginger
leaves.
Thirty days old seedlings of sweet clovers {Melolitus spp.) were
inoculated with 0, 10, 100, 1000 and 10000 larvae of M incognita I pot. It
22
was observed that the maximum reduction in plant growth occurred at the
highest level i.e. 10, 000 nematodes / 500 cc soil (Azmi, 1988).
An initial inoculum 4 J2/ g soil of M incognita significantly reduced
the growth of chilli (Capsicum annum L.) cv. Mathani i.e. 2. In contrast, the
nematode did not have any significant adverse effect on the plant growth of
cultivar 'Pusa Jwala' (Rama and Gill, 1989).
Jiji and Venkitesan (1989) studied the pathogenic effect of both,
root-knot (M incognita) and reniform nematode (/?. reniformis) at 100, 500
and 1000 numbers on plant growth parameters and yield in brinjal, alone
and in combination. Inoculum levels either of 1000 root-knot nematode
larvae / plant or 1000 reniform nematodes / plant or 500 root-knot nematode
+ 500 reniform nematode / plant were pathogenic at par affecting the plant
growth characters after 45 as well as 130 days of inoculation. An inoculum
level of 500 / plant of root-knot or 1000 number of reniform nematode
alone or in combination resulted in 29 to 48% yield reduction.
Haseeb and Butool (1989) reported that root-knot nematode, M
incognita, severely limited growth and oil yield of Ocinum sanctum L. They
noticed" that with increase in the initial inoculum level, there was
corresponding decrease in root-shoot length, fresh and dry plant weights,
and total oil yield. Intensity of host reaction (root galling) was directly
proportional to the increase in the initial inoculum level. The highest root-
knot index was foimd in plants inoculated with the maximum inoculimi
level (15000 freshly hatched second stage juveniles) and lowest at the
minimum inoculum (50 second stage juveniles). As a result of O. sanctum
with different inoculum levels of M incognita, the fresh and dry weight of
plants and the total oil yield were restricted considerately at all inoculum,
levels. The highest rate of reproduction was at the inoculum of 50 second
stage juveniles. Where as the lowest rate of reproduction was at inoculum
level of 15000 second- stage juveniles. This suppression in nematode
reproduction was probably due to the penetration of a greater number of
23
juveniles at high initial levels which suppressed root growth. The high
infection undoubtedly hindered nematode development and reproduction.
Ahmad (1989) revealed that root-knot nematode M. incognita caused
significant reduction in the growth of the black henbane (Hyoscymus niger
L.). Root-knot nematode caused significant reduction in growth of the
plants. This reduction was minimum at the lowest inoculum level (50
juveniles per plant) for length and weight. Greater reduction in length and
in weight was recorded in plants inoculated with 500 and 5000 juveniles per
plant respectively. The nematode infection also brought about a significant
reduction in the number of fruits per plant.
Pankaj and Siyanand (1990) studied the pathogenicity of M.
incognita on bitter gourd {Momordica charantia L.) and round melon
(Cucumis melo L.) by inoculating different levels of 2"''stage juveniles (J2)
of the M. incognita. Significant reduction in plant growth characters were
observed but the final nematode population increased with increase in the
inoculum levels. The damaging threshold in bitter gourd was found to be
one J2 / g of soil as against 10 J2 / g in round melon.
Nayga and Salares (1990) conducted an experiment to determine the
most susceptible stage of growth of bitter gourd to the root-knot nematode
M. incognita infestation as related to inoculum density. The plants were
inoculated with initial inoculum densities of 1000, 5000, 10,000 and 20,000
eggs. Inocula were applied at 2, 4, 6 and 8 weeks after transplanting. Plants
having highest inoculum density of 20,000 eggs per plant supported the
greatest nematode population both in the roots and in the soil. Population of
nematodes decreased significantly when plants were inoculated at 6 and 8
weeks after planting. Total fruit production (yields) in 2 and 4 weeks old
plants inoculated with 1000 and 5000 eggs were suppressed by 68 to 70%,
this changed to 81 to 82% when inoculum density was increased by 10,000
and 20,000. Percentage yield loss was lower on 8 week old plants,
regardless of inoculum density was increased. Interaction effects of
inoculum density versus age of plant on the production of galls and egg
24
masses, fresh vine weight, and weight of marketable and non-marketable
fruits were significant.
Govindaiah et al. (1991) observed the effect of different inoculum
levels of M incognita viz. 0,10,100,1000 and 10,000 second stage larvae /
plant and extent of avoidable leaf yield loss were estimated in pot culture
and field conditions respectively. Meloidogyne incognita was found to be
highly pathogenic to mulberry {Moms alba L.) and caused significant
reduction in plant growth leaf yield and moisture percent as well as shoot
and root weight were at 10,000 larvae / plant.
Khan and Hussain (1991) observed that with increasing inoculum
levels of M. incognita there was a corresponding increase in the plant
growth reduction of papaya (Carica papaya L.) However, it was not
statistically significant at the inoculum levels up to 500 nematodes larvae /
plant. Inoculation of 2000 juveniles / plant, on the other hand caused
significant reduction in growth. Reproduction factor (Rf) of root knot
nematode was significantly reduced with increase in the inoculum levels of
M. incognita.
Munawar et al. (1991) the lentil plants were adversely affected by
the root-knot nematode. Reduction in plant length, fresh and dry weight and
nodulation were found significant at the inoculum level of 10 or more root-
knot nematode (M incognita. The percentage reduction in plant length,
fresh and dry plant weight and nodulation of lentil cv. L-209 was inversely
related to initial levels of nematode populations. In lentil cv. Lens- 830 at
the lowest inoculum level (100 juveniles) there was stimulation in plant
length and fresh weight while dry plant weight and nodulation showed
reductions at this inoculum level. However, with fiirther increase in the
moculum level there was decrease in all plant growth characters.
The root-knot nematode, Meloidogyne incognita caused significant
reduction in plant growth of okra (Abelmoschus esculentus cv. Pusa
Sawani.) and with an increase in initial inoculum of M incognita, from 50
to 5000, there was a gradual decrease in plant growth characters and water
25
absorption capacity of plant roots. A population level of 50 juveniles of M
incognita per kg of soil was the marginal threshold level for producing
measurable effects on the growth of okra. The host infestation and
nematode multiplication were found to be density dependent. The number
of galls, egg masses and number of eggs / egg mass were found to be
directly proportional to the increasing inoculum of the nematode. The final
population was maximum at the inoculum level of 5000 juveniles but the
rate of population increase (R. P. I.) of the nematode was highest where in
50 juveniles were used (Sharma and Trivedi, 1991).
Poomima and Vadivelu (1992) studied the pathogenic effect of
nematodes viz. M. incognita, R. reniformis and Pratylenchus delatirei Luc,
1958 individually as well as in different combination under glasshouse
condition on brinjal cv. Co2. The results indicated that the reduction in
shoot height and weight, root length and weight and number of leaves
occurred as a result of the individual nematode species attack. Root-knot
nematode was relatively more damaging than others. The multiplication
rates of the individual nematode species was the greatest when alone and
were reduced significantly when present as combinations. Study of
interaction effects of the nematode species, revealed that MJncognita and R.
reniformis was more antagonistic to each other while, R. reniformis was
more antagonistic to P. delatirei than M. incognita. Among the species,
root-knot nematode was the dominating population. The extent of galling
and lesion formation was also maximum in the individual inoculation and
the least in combinations.
The significant reductions in root / shoot length, plant fresh / dry
weights and oil yield of Indian basil Ocinum basilicum L. were noticed at
all initial inoculum densities(Pi) of M incognita. Highest reduction in root /
shoot length, fi-esh / dry weight of plant and oil yield was obtained at
highest Pi (16000 J2). Highest reproduction rate was found at lowest Pi (500
J2), whereas, root knot index increased with increase in inoculum densities.
Thus, nematode multiplication rate was found inversely proportional to the
26
extent of yield losses and root-knot index was proportional to plant damage
(Uaseehetal., 1993).
Eapen (1994) studied the relationship between the logarithmic series
of five initial densities (Pi) of M incognita (0 to 400 nematodes / 100 cm^
soil) and growth as well as yield of a susceptible accession of small
Cardamom (Elettaria cardamomum L.). Maximum growth suppression and
yield loss were noticed at Pi = 4 nematodes / 100 cm^ soil .The earliest
visible damage due to nematode infestation was observed as reduction in
number of tillers. However, stunting and narrowing of leaves were observed
at the fag end of the trial. Non significant difference was noticed in the final
nematode densities in roots of cardamom plants of different Pi. The
nematode population stabilized after initial temporal changes as a result of
the self regulatory, density dependent processes with time. Damage caused
at the early part of growth phase of cardamom plants was critical to final
yield and crop stand.
Patel et al .(1996) reported that the inoculum level of 1000 second
stage juveniles (J2) of either Meloidogyne incognita or M. javanica per plant
was detrimental to cotton cv. Hybrid S.Total nematode population build up
of both species increased with an increase in inoculum levels fi-om 10 to
10000 J2 / plant. However, nematode reproduction rate decreased with an
increase in nematode population. Nematode infection significantly
increased leaf temperature and decreased relative humidity and transpiration
rate of plants. Infection of M. incognita at 5000 and 10000 J2 / plant
decreased peroxidase and polyphenoxydase activities.
Singh and Nath (1996) found that with increasing inoculum level of
M. incognita there was gradual reduction in plant growth characters except
at initial inoculum level of 10 nematodes. Better plant growth at 10
nematode population can be attributed to production of more roots to
counteract the light infection of plant which was much below the damaging
threshold level. Initial population of 10 M. incognita per 500g of sandy
loam soil to be pathogenic level for papaya plants.
27
Kumar and Singh (1997) found that there was progressive decrease
in length and weight of shoot and root with the increase in the initial
inoculum level of M. incognita. Multiplication of nematode in soil on
Japanese Mint {Mentha arvensis L. sub. sp. haplocalyx Briquet var.
piperascens Holmes) after 90 days of inoculation was found to be density
dependent. However, the decrease in nematode multiplication rate at the
highest nematode inoculum level was perhaps due to competitions for
nutrition among the developing nematodes within available root system and
also due to inability of juveniles of subsequent generation to find infection
sites. The rate of multiplication was higher, at low inoculum level as
compared to high inoculum levels.
Inoculation of 100 or more M. incognita nematodes per pot showed
suppression of plant growth of gladiolus {Gladiolus hortulanus Bailey) after
45 days of inoculation. Highly infested plants with inoculum levels of 1000
and 10,000 looked short, weak and pale with shriveled leaves and delayed
emergence of spike. These levels of the nematode also caused significant
reduction in number of leaves, leaves per spike and root weight. There was
no emergence of plants at the highest inoculum level of 10,000 h-
Production of corms per plant was similar in the control and the treatment
receiving up to 1,000 nematode. Only the pots with 10, 000 nematodes
indicated the reduction in corm production as compared to control. Cormel
production was adversely affected at the initial inoculum levels of 1,000
and 10,000 nematode as compared to control was inoculated. Nematode
population revealed that the rate of multiplication was greater in the pots
with lower initial population and at 10,000 initial level, there was reduction
in final nematode count. An increase in root-knot gall index corresponded
to increase in nematode inoculum levels. Statistically the gall index in the
treatments of 10 and 100 J2 per pot were significantly different from the gall
index recorded from the plant roots inoculated with 1, 000 and 10, 000
nematodes (Khanna and Chandel, 1997).
28
An initial inoculum level of 100 juveniles of Meloidogyne incognita
per plant caused significant reduction in fresh and dry fibrous root weight
and tuber yield and proved to be pathogenic to Dioscorea rotundata Poir.
Severe well pronounced large sized galls were noticed in plants which
received an initial inoculum of 100 hi plant or more. The multiplication
rate of the nematode was maximum at lowest level of inoculimi (10 J2) and
minimum at the highest level of 10,000 h (Mohandas and Ramkrishnan,
1997).
Poomima and Vadivelu (1998) studied the pathogenicity of
Meloidogyne incognita Race-3 on turmeric {Curcuma longa L. cvs. BSR-1
and PTS-10) .The nematode was pathogenic at 5000 and 10,000 J2 / plant,
inoculated 15 days after planting. The leaves of the inoculated plants were
pale in colour and shoot weight reduced by 6-10 % in both varieties.
Rhizome yield reduction in cv.BSR-1 was 25 and 18.6% at 5000 and \0,
000 nematodes / plant, respectively while it was 48.2 and 41.3% at these
inoculum levels for PTS-10. In both the turmeric cultivars, the levels of
protein, carbohydrate chlorophyll a, b, and total rhizome curcumin levels
were lower in plants inoculated with 10, 000 juveniles when compared to
healthy ones. It was concluded that the nematode caused loss in yield as
well as quality of the produce in turmeric.
Ramkrishnan and Rajendran (1998) studied the effect of individual
and concomitant inoculation of M. incognita (Race-3) and Rotylenchulus
reniformis at 10, 100, 1000 and 10000 nematodes on growth and
physiology of papaya cultivar C0.6. Both the nematodes were found as
pathogenic at a level of 1000 nematodes per plant with pathogenicity more
severe under the former. When both the nematodes were present the
pathogenic effect of M incognita was lowered. At the pathogenic level, M.
incognita caused reduction in total chlorophyll 'a' and 'b' content. The leaf
temperature increased accompanied by higher rate of evaporation and
lowered photosynthesis.
29
Inoculation of turmeric plants with 100 infective stages of root-knot
(Meloidogyne incognita) and reniform nematodes as initial inoculum level
caused significant reduction in growth characters. Reniform nematode
appeared to be more harmful than root-knot by producing significantly
higher grow^ reduction at lower level. Gall formation due to root-knot
nematode was adversely affected by their combined inoculation (Haider et
al, 1998). Patel et al. (1998) indicated that an inoculum level of 10,000 M.
incognita and 50,000 M. javanica h and above / plant induced significant
reduction in the growth of banana cv. Basarai. Plant growth was
significantly reduced when M. incognita were inoculated at 10 J2 /g soil.
Nematode multiplication rate was significantly low at 10.0 J2 /g soil
whereas at 0.01 and 0.10 J2 /g soil, there was an increase in the nematode
multiplication rate (Kumar, 2000).
Desaeger and Rao (2000) tested the effects of six inoculum levels (0,
80, 400, 8000, 2000 and 4000 eggs per lOOcm^ soil) of Meloidogyne
javanica on nematode multiplication and growth of two Sesbania sesban
Merrill grown in provinces (Kakamega and Kisii) in six soils with sand
contents of 26 to 82 %. At one month after sowing, nematode infection, gall
index and seedlings mortality increased with inoculum level and sand / clay
ratio. Gall index decreased and seedling growth improved with extractable
cations, particularly calcium. At three months, nematode infection and
damage were affected neither by soil texture nor by extractable cations.
However, nodulation and plant growth decreased with increasing inoculum
levels in all soils. Soils with higher cations and inherent fertility were less
prone to nematode infestation and sustained better sesbania growth
irrespective of soil texture. It appears that as sesbania grows it develops
tolerance to M. javanica, suggesting that nematode infection is important at
seedling stage primarily in determining stand establishment and early
growth. Kisii province was more tolerant to the nematode and more
productive than Kakamega. There is need for screening a wide rage of
sesbania germplasm for nematode resistance to select appropriate provinces
30
and exploring low cost methods to minimize nematode damage to sesbania
at establishment stage.
Six initial population densities Pi = 0, 2000, 4000, 6000, 8000 and
10,000 eggs per 1200 cm^ soil of two root-knot nematode species M.
incognita (Mi) and M. javanica (Mj) and four potting media (sand, sand /
vermiculite, vermiculite, and fafard) were used to evaluate nematode
parasitism of seedlings of 'Lovell' Peach {Prunus persica L. Batsch) root
stock under green house conditions. There were no significant difference in
plant height, shoot dry weight and root dry weight among different Pi
treatments and different medium treatment for either nematode spp, except
that the peach grown in fafard medium had greater plant height, shoot dry
weight and root dry weight. The results indicated that at Pi of 4,000 Mi or
Mj eggs /1200 cm soil was needed to produced reliable nematode infection
on peach roots for the evaluation of the host susceptibility and sand /
vermiculite was a suitable medium for root-knot infection and reproduction
on susceptible peach root under green house condition (Zhen-xian et al,
2000).
Perveen et al (2001) carried out an experiment in the earthen pots to
study the influence of Meloidogyne incognita on plant growth, chlorophyll
content and oil yield of Mentha arvensis cv. Gomti. They showed that
increase in initial population densities (Pi = 0, 500, 2500, 5000, 2000 and
25000 J2 of Meloidogyne incognita I pot) a considerable increased reduction
in the shoot length, root-shoot length fresh and dry weight. Total sugar.
Phenol, chlorophyll a, b and total chlorophyll content in leaves were also
decreased with increase to the Pi of M. incognita. Mostly there was no
significant difference in different parameter between two corresponding Pi.
Final nematode population in roots and suckers in soil and root-knot index
was observed to be directly proportional to Pi while reproduction factor was
inversely proportional to Pi.
Pathogenic effect of M. incognita Race-2 on onion (Allium cepa L.)
was studied by inoculation of different levels of second stage juvenile (.T2)
3i
viz. 0, 10, 100, 500, 1000, 5000, 10000 in 500 cm^ sterile soil in earthen
pot. The plant growth parameters shoot length and weight of onion bulbs
were significantly reduced in all the inoculated plants over control.
Inoculated plants also showed severe pruning and decaying of roots. The
nematode could reproduce well on onion as it was evident form the egg
mass index the highest nematode multiplication rate was observe at the
inoculum level of 10 J2 / 500 cm'' soil. The damage threshold level of M
incognita Race-2 was found about 10 J2 / 500 cm . (Khan et al, 2001).
Khan (2003) studied the pathogenicity of M. incognita on onion plants by
inoculating with second stage juveniles of M. incognita Race-2, with
different inoculum levels 10, 100, 500, 1000, 5000, 10,000. Ten juveniles /
500cc soil could cause significant reduction in weight of onion bulbs. The
plant growth of balsam (Impatiens balsamina L.) was significantly reducted
at 1000 hof Meloidogyne incognita Race-2 per lOOOcc soil (Khan, 2003).
Pathak et al. (2003) showed a significant decreased in germination
and seedling emergence of cauliflower {Brassica oleracea var. botrytis L.)
at 500 nematodes / kg soil which further decreased with increase in
inoculum level. Seed germination and seedling emergence were more in
unsterilized soil than sterilized soil. Plant growth characters were adversely
affected with an increase in the level of inoculum from50-1000 juveniles /
kg soil. Significant reduction in growth characters could be noticed at and
above the level of 500 nematodes / kg soil.
Pathogenic effect of M. javanica on bitter gourd {Momordica
charantia L.), bottle gourd (Lagenaria siceraria (Mol.) Standi.) red gourd
(Cucurbita maxima Duch. ex. Lam.) and sponge gourd (Luffa cylindrica (L)
Roxb.) were studied by inoculation of different inoculum level of second
stage juveniles (J2) viz. 0, 250, 500, 1000, 2000, 4000 and 8000 h I Kg
sterilized soil in earthen pots. Significant reduction in growth of bottle
gourd and red gourd was recorded at initial inoculum level of 1000 J2 / kg
soil of M. javanica which was damaging threshold level. Similarly, the
damaging threshold level for M. javanica on sponge gourd and bitter gourd
32
were recorded at the inoculum level of 500 and 2000 J2 / kg of soil,
respectively. An increase in the level of inoculum showed a progressive
increase in host infestation as indicated by number of galls as well as
nematode multiplication. Maximum nematode multiplications in all tested
plants were observed at the lowest inoculum density and vice versa (Khan
et al, 2004).
Park et al. (2005) the pathogenic potential and reproduction fitness
oi Meloidogyne hapla Chitwood, 1949 on three species of medicinal plants;
Angelica koreana, Peucedamum japonicum and Astragalus memberanaceus
was determined under greenhouse conditions. A significant damage was
observed in shoot and root length, weight and root-diameter of these plants
by all Pi levels at 90 days post inoculation. The plant damage increased
with increase in Pi up to 5000 (J2) and caused significant reduction in root
weight of A. koreana, P. japonicum and A. memberanaceus respectively.
The greater intensity of root gall severity was observed on A. koreana and
P. japonicum then on A. memberanaceus at all Pi levels 1000, 2000, 3000,
4000, 5000 and 10,000 juveniles (J2) / kg soil. At 5000 h root gall severity
was 5.0, 5.0 and 3.0 on A. koreana, P. japonicum and A. memberanaceus,
respectively. Increasing rate of Pi exponentially reduce reproduction factor
of M. hapla on all of these medicinal plants. However it was higher on A.
koreana and P. japonicum. Khan and Ashraf (2005) found that inoculum
level of 2000 second stage juveniles (J2) of Meloidogyne incognita and
1000 J2 of Meloidogyne javanica per plant were pathogenic to lettuce
(Lactuca sativa L.). With increase in the inoculum level from 250-8000 J2 /
plant there was corresponding increase in plant growth reduction and total
population build up of nematodes.
Khan et al. (2006) evaluated the effect of different inoculum levels
viz. 0, 250, 500, 1000, 2000, 4000 and 8000 juveniles of Meloidogyne
javanica on hTocco\i{Brassica oleracea vzx.italica Pleorek) The analysis of
data revealed that population level of 1000 juveniles / kg soil was
associated with significant decline in plant growth and was thus indicative
of being pathogenic level.
Khan et al. (2006) conducted an experiment to s ady the effect of
different inoculum levels viz. 0, 250, 500, 1000, 2000, 4000, and 8000
second stage juveniles of M. javanica h I plant on balsam. The results
indicated that an inoculum level of 500 and above h I pJant significantly
decreased the height and dry weight of the plants. Nimiber of galls per root
system and root-knot nematode population in soil and roots progressively
increased with an increase in nematode inoculum levels from 250 to 8000 J2
/ plant. Nematode reproduction rate decreased with an increase in nematode
inoculum levels. It was maximum in the level of 250 J2 / plant and
minimum on the level of 8000 J2 / plant. Nematode inoculated plants
exhibited symptoms such as stunted growth, yellowing and dropping of
leaves at and above 500 J2 / plant. This clearly indicated that 500 and above
second stage juveniles of M. javanica I plant was detrimental to plant
growth.
Lall and Das (1959) have reported that Meloidogyne incognita var.
acritu completed its life cycle on egg plant {Solanum melongena) in 40.8
and 20.8 days in January and Jime respectively. Dhawan and Sethi (1976)
observed that M. incognita required 36 days to complete its life cycle on
little leaf affected egg plants. Kaushik and Bhatti (1986) noticed that the
temperature had a marked effect on the development of M. javanica.
Penetration of juveniles took 48 hrs at comparatively high temperature
period (October-December), than at lower temperature (December-March),
when it tooks 96 hrs. The same trend was noticed in all the developmental
stages up to the formation of mature females. Oviposition commenced on
51 days during February / March compared to 21 days during June / July.
The average niraiber of eggs laid per egg mass was more (124-126) during
March / April and less (70-78) during Jime / July. Time taken for
completion of life cycle was much less in June / July (26) days 31-42 days
in March and July, but extended to A6-66 days during (October- December).
34
Gaur and Khan (1992) described the new species of cereal root-knot
nematode, Meloidogyne sp. completed its life cycle from J2 to J2 on wheat
cv. HD 2329 in 31 days in November and 26 days in March and on rice cv.
Pusa Basmati -1 in 25-28 days in March and July. The percent invasion was
relatively more on rice whereas proportionately more of 'nvading juveniles
attained maturity on wheat. The percentage emergence of rice seedlings was
significantly reduced at 2.0 second stage juveniles (J2) per cc of soil. The
shoot growth of young rice and wheat plants was significantly reduced at
0.5 and 1.0 J2 per cc of soil. This root-knot nematode species prefers
graminaceous hosts and seems to be adapted to the relatively low and high
moisture regimes under wheat and irrigated upland rice, respectively.
Patel et al. (1992) indicated that M. javanica @ 100 J2 / plant and
above was detrimental to the growth and development of pigeon pea. Total
nematode population / plant significantly increased progressively with an
increase in nematode population from 10 to 10,000 / plant. Nematode
reproduction rate was maximum at 10 and minimum at 10,000 nematodes /
plant. Roots inoculated with 5000 and 10,000 J2 / plant had higher
peroxidase, polyphenol oxidase and total phenol contents over confrol.
Biological studies of M incognita on French bean cv. 'Pusa Parvati'
was conducted in glass house at room-temperature of 22°C at day and ll'^C
at night. Penetration of 2"^ stage juveniles (J2) started within 12 hours and
continued till 48 hours after inoculation. Maximum penetration was
recorded at 48 hours inoculation. After penefration the juvenile remained in
its vermiform stage for approximately 6 days. The second and third moult
occurred by 8* and 14 ' day after inoculation the juveniles were still
observed to be non-feeding. They gradually enlarged to acquire a
inoculation the fourth and final moult from preadult stage to become adult
male and female occurred. Adult females oviposited after 24 days of
inoculation .The total life cycle of M. incognita was completed after 31
days of inoculation, when the first hatched J2 was recorded from egg mass
(Mohan and Mishra, 1994).
35
Singh and Kumar (1998) indicated that second stage juveniles of M
incognita started invading the young mint roots 48 hours after inoculation.
Maximum penetration of J2 was observed on the 5* day after inoculation
(43%) and continued up to 16 days of inoculation. Second moult occurred
on 5* day after inoculation indicating the appearance of third stage with
posterior ends round with spike tail. Third stage lasted for 4 days when third
mouh occurred resulting into 4"' stage male and female juveniles. A
valvular plate in the fourth moult was observed on 18'*'day after inoculation
resulting into mature female and male. Deposition of gelatinous matrix
without any egg was observed on 22" * day after inoculation. Second
generation J2 were appeared on 29'*'day after inoculation. Thus, life cycle of
M. incognita on Japanese mint {Mentha arvensis) cv. 'Shivalik' was
completed from J2 to h in 29 days at ambient temperature 13°C-37°C
during March and April.
Sujatha and Mehta (1998) observed that Pratylenchiis zeae Graham,
1951 and Meloidogyne javanica were important plant parasitic nematodes
in the sugarcane {Sacchamm officinarium L.) growing beUs of Tamil Nadu.
Since they are fi^equently identified together in the same field it is necessary
to study the life cycle of both the nematode individually and in
concomitance. Pratylenchus zeae individually takes 18-20 days firom J2to J2
under lath house conditions to complete its life cycle while M. javanica
takes 55 days. But, when the two nematodes were moculated together the
life cycle P. zeae was not interrupted together at any stages and was
completed as when individually inoculated at 18 days. However, the life
cycle of M javanica was suppressed by Pratylenchus zeae as it took more
number of days to complete its life cycle with reduced number of eggs in
gelatinous matrix.
Jothi and Babu (1998) found that Meloidogyne incognita is an
important nematodes pest of vegetable crops. A life table for M. incognita
on tomato {Lycopersicon esculentum Mill.) was developed 29°C and 31°C.
Mortality rate was higher during J2 stages prior to root penetration. The
36
nematode penetrated the roots on 3' '' day after inoculation. At 29^C the
females with egg mass were observed on 21 ' day and at 31°C the females
with egg mass were observed on lA^ day.
Mahapatra and Swain (1999) reported that life cycle (J2-J2) of M
incognita on black-gram cv .1-9 was completed within 32 days at a
temperature range of 18-34*'C. The juveniles starting penetrating roots as
early as 12 hrs after inoculation and continued up to 6 * days. Initiation of
mouhing in h was observed at 8* day of inoculation and completed on 14
day. Third moulting started on 16"' day and was completed on 22" " day of
inoculation and young females developed. Matured females secreted egg
sacs at 26"' day of inoculation. They ftirther observed that life cycle of M
incognita was delayed by two days in the presence of Fusarium oxysporum.
Verma and Anwar (1999) studied the penetration of second stage
juveniles of M. incognita in roots of pointed gourd (Trichosanthes diocia
Roxb.) continued up to 9 days with maximum numbers penetrating on 6
day. After penetration, the juveniles oriented themselves longitudinally near
the vascular area behind the root tip and started moulting in 72 hrs. Young
females appeared 18"" day after inoculation. Deposition of gelatinous matrix
and egg masses started from 20-24 days followed by emergence of J2 (2"**
generation). Majority of eggs were retained in the egg masses. The number
of eggs varied from 50-385 per egg mass. The larval penetration in roots
resulted in the formation of necrosis and irregular shaped giant cells. The
infection also caused the formation of confluent roimd to spindle shaped
galls laterally on roots.
Sharma et al. (2000) reported that M. incognita completed its life
cycle fi-om second stage juveniles to the formation of adult female with egg
mass in 29 days on groundnut plants. Khan (2001) studied the life cycle of
M. incognita race 2 on balsam showed that the life cycle (J2 to J2) was
completed within 27 days at the temperature ranging between 22°C to 35°C.
Khan (2002) reported that the penetration of M incognita juveniles in
papaya roots was reduced in the presence of Fusarium soiani. Only 66.3%
37
penetrated juveniles developed into females in M. incognita alone in
comparison to 42.7%, where F. solaini was present along with M.
incognita. Fecundity was also reduced with an average of 207 eggs per egg
mass in roots infected with M. incognita and F. solani as compared to 356
eggs with M. incognita alone. Moreover, the percentage of male was high
(7.3) in roots infected with M. incognita and F. solani. Presence ofF. solani
delayed the life cycle of the root-knot nematode by 9 days. Life cycle of
root-knot nematode, Meloidogyne incognita Race-2 completed within 27
days at 22-33°C (Khan, 2003).
Khan and Ashraf (2005) studied life cycle Meloidogyne incognita
and Meloidogyne javanica required 32 and 29 days respectively to complete
their life cycle on lettuce at a temperature ranging between 18-25°C.
Khan et al. (2006) reported the root-knot nematode Meloidogyne
javanica required 27 days to complete its life cycle on broccoli at a
temperature ranging between 22-28°C. Khan et al. (2006) reported that the
life cycle of M. javanica on balsam was completed within 23 days at a
temperature ranging between 25-30* 0.
38
MateriaCs
Methods
CHAPTER-3
MATERIALS AND METHODS
Two species of root- knot nematodes, Meloidogyne incognita Race-1
and M. javanica were selected as test pathogens. Lablab bean {Dolichos
lablab var. Glory) and mung bean {Vigna radiata var. Jawahar 45) were
taken as test plants for experiments.
3.1 PREPARATION AND STERILIZATION OF SOIL MIXTURE:
Sandy loam soil collected from a fallow field of Aligarh Muslim
University campus was sieved through 16 mesh sieve and mixed with
sieved river sand and organic manure in the ratio of 3:1:1, respectively.
Throughout the course of studies, 6 inch pots were filled with this soil
mixture @ 1 kg / pot. A little amount of water was poured in each pot to
just wet the soil before transferring to an autoclave for sterilization at 201b
pressure for 20 minutes. Sterilized pots were allowed to cool down at room
temperature before use for experiments.
3.2 RAISING AND MAINTENANCE OF TEST PIANTS:
Seeds of the mung bean and lablab bean were surface sterilized with
0.1% mercuric chloride (HgCl2) for 2 minutes and washed thrice in
sterilized distilled water and treated with mung bean and lablab bean strain
of Rhizobium before sowing. Sucrose solution (5%) was used as sticker for
bacterization. The bacterized seeds, dried at room temperature, were sovra
in each pot @ 5 seeds / pot and after their germination thirming was done so
as to maintain only one plant per pot. Two weeks old well-established and
healthy seedlings were used for experimental work.
39
3.3 RAISING AND PREPARATION OF NEMATODE INOCULUM:
The pure culture of Meloidogyne incognita Race-1 and M javanica
was raised on brinjal plants, using a single egg mass collected from infected
plants of brinjal. The egg mass of each species of root-knot nematode was
surface sterilized by treating it with 1:500 aqueous solution of chlorox
(calcium hypochloride) for 5 minutes. Treated egg mass was washed thrice
in distilled water. The eggs in the egg mass were allowed to hatch out at 28
± 2°C under aseptic conditions on a sieve layered with tissue paper and kept
in a Petridish containing sufficient amount of sterilized distilled water.
Seedlings of brinjal grown in 12 inch clay pots, containing sterilized soil
were inoculated with the juveniles so obtained. Nematodes were extracted
from the soil after two months, according to Cobb's sieving and gravity
method followed by Baermann funnel technique (Southey, 1970).
Nematodes so obtained were used for inoculating fresh eggplant seedlings
growing in 12" clay pots containing sterilized soil. Second stage larvae of
root-knot nematode infected the roots and multiplied.
After 2-3 months, the egg masses from heavily infected roots of
brinjal on which pure culture of Meloidogyne incognita or Meloidogyne
javanica multiplied were handpicked with the help of sterilized forceps.
These egg masses after being washed m distilled water were placed in a
sieve with a layer of double tissue paper. The sieve was placed over
Petridish (10 cm in diameter) containing water. The water level was kept
such that it just touched the lower portion of the sieve having egg masses. A
series of such assemblies were kept to obtain large number of second stage
juveniles required for inoculations in the experiments. After every 24 hours,
the hatched out larvae were collected alongwith water from the Petridish in
a beaker and fresh water added to the Petridishes.
The water suspension of each Meloidogyne species separately was
thoroughly stirred for making homogenous distribution of nematodes before
taking 2 ml of suspension in the counting dish for counting the number of
nematodes under the stereoscopic microscope. An average of five counts
40
were taken to determine the density of nematodes in the suspension.
Volume of water in the nematode suspension was so adjusted that each ml
contained about 100 nematodes, which was done by either adding more
water or decanting the excess amount of water so that 10 ml of this
suspension contained 1000 second stage juveniles of root-knot nematode.
3.4 INOCULATION TECHNIQUES:
Feeder roots of seedlings, of either mung bean or lablab bean, just
before inoculations were exposed by carefully removing the top layer of
soil and the required quantity of nematode suspension inoculum was poured
uniformly all around the exposed roots using sterilized pipette. Exposed
roots were immediately covered by levelling the soil properly. Untreated
and uninoculated plants served as control. Each treatment was replicated
three times and suitably randomized on a glass house bench. Watering was
done as and when required.
3 . 5 EXPERIMENTS:
3 . 5 . 1 PATHOGENICITY OP ROOT-KNOT NEMATODES:
In order to study the pathogenicity of root-knot nematodes viz. M.
incognita and M. javanica, three week old well established seedlings of
mung bean and lablab bean were inoculated with 250, 500, 1000, 2000,
4000 and 8000 fresh second stage juveniles (J2) of either M. incognita and
M. javanica per plant. There were separate sets for each nematode species
in both the test plants. Uninoculated plants served as control and each
treatment was replicated thrice.
3 . 5 . 2 STUDIES ON THE LIFE CYCLES OF MELOIDOGYNE
INCOGNITA AND MELOIDOGYNE JAVANICA ON MUNG
BEAN AND LABLAB BEAN:
To study the life cycle of root-knot nematodes on mung bean and
lablab bean, two weeks old seedlings of test plants were transplanted into 6
41
inch earthen pots containing 1 kg sterilized soil + river sand + farm yard
manure (3:1:1) mixture. After 24 hours of transplantation, 100 seedlings
were inoculated with freshly hatched 1000 second stage juveniles of
Meloidogyne incognita or Meloidogyne javanica.
Observations on penetration and developmental stages of the
nematode the completion of life cycle. The complete root system of each
seedlings was carefully removed from the soil, washed gently in tap water
and stained ui 0.05% boiling lactophenol acid fuchsin (Franklin, 1949)
followed by were recorded from three seedlings after every 24 hours and
continued till washing in tap water and keeping in plain lactophenol for
further differentiation. Lactophenol-acid fuchsin staining solution was
prepared by mixing Phenol (20g), Lactic acid (20 ml), Glycerine (40ml) and
water (20ml). The 5 ml of the solution (Ig acid fuchsin +100 ml of water)
was added to this mixture.
Developmental stages (A, B, C, and D & E) of the nematode were
identified as described by Triantaphyllou and Hirschmaim (1960):
A= Pre-parasitic Ilnd stage juveniles (filiform shaped).
B= Parasitic End stage juveniles (spindle shaped).
C= Illrd and IVth stage juveniles (sausage shaped).
D= Moulted IVth stage juveniles (moulted sausage shaped).
E= Adults (females and males) sac and filiform shaped respectively.
3 . 6 RECORDING OF OBSERVATIONS:
I ) PLANT GROWTH DETERMINATION:
Plants were uprooted after 60 days of inoculation and roots were
washed thoroughly in slow running tap water. Utmost care was taken to
avoid loss and injury of root system during the entire operation. For
measuring length and dry weight, the plants were cut with a sharp knife just
above the base of root emergence. Length of shoot and root was recorded in
centimeters from the cut end to the tip of first leaf and the longest root
respectively. For measuring dry weight, the shoots and root were kept in
42
envelops separately for drying in an oven running at 80°C for 24 hours and
the weight was recorded in grams. For interpretation of results, the
reduction in plant growth was calculated in terms of percentage dry weight
reduction.
I I ) ROOT GALLING ESTIMATION:
The galling caused by root-knot nematodes was estimated by
counting the number of galls per root system.
III) ROOT-NODULE ESTIMATION:
Nodulation was estimated by counting the number of nodules per
root system.
IV) NEMATODE POPULATION ESTIMATION:
For extraction of nematodes, the soil from each treatment was mixed
thoroughly and a sub-sample of 200g soil was processed through sieves
according to Cobb's sieving and gravity method followed by Baermarm
funnel technique. Each suspension was collected in a beaker and volume
made up to 100ml. For proper distribution of nematodes, the suspension
was bubbled with the help of pipette and 2ml suspension of each sample
was drawn and transferred to a counting dish. The number of nematodes
was counted in three replicates for each sample. Mean of three such
counting's was calculated and the final population of nematodes / kg soil
was determined.
To estimate the nematode population in roots, l.Og root from each
replicate was macerated with enough water in an electrically operated
waring blender for about 30 to 40 seconds. The macerate was collected in a
beaker and volume made up to lOOral. The nematode population was
counted as described above. Reproduction factor of nematode was
calculated by the formula R = Pf / Pi, where "Pf represented the final and
"Pi" the initial population of the nematode.
43
V) STATISTICAL ANALYSIS:
The data obtained were analyzed statistically and significance was
calculated at P = 0.05 and P = 0.01 levels of probability.
44
CHAPTER-4
RESULTS
4 . 1 STUDIES ON THE PATHOGENICITY OF MELOIDOGYNE
JAVANICA ON MUNG BEAN {VIGNA R2WIATA
L.VAR.JAWAHAR 45):
It is evident from the data presented in Table-1.1 that the plant
growth reduction of mung bean was directly proportional to the inoculum
level i.e. with increasing inoculum level from 250 to 8000 juveniles of
Meloidogyne javanica {h) per plant, there was a corresponding reduction in
plant growth of mung bean. The inoculation of plants with 250, 500, 1000,
2000, 4000 and 8000 Jj/plant resulted in 1.8%, 3.8%, 6.7%, 27.2%, 38.0%
and 45.5% reduction in plant growth of mung bean, respectively. The
inoculum levels up to 1000 h I plant did not show significant reduction in
plant growth as compared with the control. Moreover, the significant
reduction in plant growth was recorded at and above 2000 J2 / plant. The
reduction in plant growth was not significant between inoculum levels of
4000 and 8000 J2 / plant. There was a significant reduction in pod weight at
and above the inoculum level of 2000 J2 / plant. The reduction in pod
weight was 30.2%, 37.5% and 46.4% in the plants inoculated with 2000,
4000 and 8000 J2 / plant, respectively. Nodulation was also significantly
reduced with an increase in inoculum levels except 250 J2 which slightly
increased nodulation as compared to control. The reduction in nodulation
was 2.2 %, 4.3 %, 30.4 %, 37 % and 45.6 % in the inoculum levels of 500,
1000, 2000,4000 and 8000 J2/plant, respectively.
The data presented in Table- 1.2 showed that the final population
of M javanica was highest in and around the plants inoculated with 8000 J2
/ plant and the lowest population was recorded in and around the plants
inoculated with 250 J2 / plant. A significant linear relationship was found
between the initial inoculum level and the fmal population of the nematode
i.e. the reproduction factor was significantly reduced with an increase in the
45
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inoculum level from 250 to 8000 J2/plant. The reproduction factor in the
plants inoculated with 250, 500, 1000, 2000, 4000 and 8000 h I plant was
10.8, 9.1, 7.7, 6.4, 3.6 and 1.8, respectively. The number of galls/root
system produced by M.javanica was 5, 15, 32, 68, 91 and 140 in the plants
inoculated with corresponding inoculums.
4.2 STUDIES ON THE PATHOGENICITY OF MELOIDOGYNE
INCOGNITA ON MUNG BEAN (VIGNA R2WIATA
L.VAR. JAWAHAR 45) :
It is evident from the data presented TabIe-2.1 that the plant growth
reduction of mung bean was directly proportional to the inoculum level
from 1000-8000 J2 of M. incognita I plant. There was a significant
reduction in plant grov^h of mung bean except in the plants inoculated with
250 and 500 J2 / plant, in which the plant growth was significantly increased
as compared to control. The inoculation of plants with 1000, 2000, 4000
and 8000 J2/ plant resulted in 31.8%, 40.9%, 50.0% and 54.5% reduction in
plant growth of mung bean plants, respectively. The significant reduction in
plant growth was recorded at and above the inoculimi level of 1000 h I
plant. The plant growth was not significant between the inoculum levels of
4000 and 8000 J2 / plant. The significant reduction in pod weight was also
recorded at and above the inoculum level of 1000 J2 / plant. The reduction
in pod weight was 4.2%, 1.8%, 20.0%, 24.6%, 29.3% and 34.8% recorded
in the plants inoculated with 250, 500, 1000, 2000, 4000, 8000, J2 / plant,
respectively. Nodulation was also significantly reduced with an increase in
inoculum level except 250 J2 which slightly increased nodulation as
compared to control. The reduction in nodulation was 3.6 %, 20.0 %, 29 %,
40.0 % and 50.9 % recorded in the plants inoculated with 500, 1000, 2000,
4000 and 8000 J2/ plant respectively.
The data presented in Tabie-2.2 showed that the final population of
M. incognita was highest in and around the plants inoculated with 8000 J2 /
plant and the lowest population was recorded in and around the plants
46
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inoculated with 250 J2 / plant. A significant linear relationship was found
between the initial inoculum level and the final population of the nematode
i.e. the reproduction factor was significantly reduced with an increase in the
inoculum levels from 250-8000 J2 / plant. The reproduction factor in the
inoculums levels viz. 250, 500, 1000, 2000, 4000 and 8000 J2 / plant was
14.2, 12.0, 10.4, 8.0, 3.2 and 2.0, respectively. The number of galls per root
system was 15, 28, 60, 72, 89, and 105 noticed in the plants with
corresponding treatments.
4.3 STUDIES ON THE PATHOGENICITY OF MELOIDOGYNE
JAVRNICA ON LABLAB BEAN (DOLICHOS LABLAB VAR.
GLORY) :
It is evident from the data presented in Table-3.1 that the plant
growth reduction of lablab bean was directly proportional to the inoculum
levels from 250-8000 juveniles oi M. javanica (J2) / plant. The inoculation
of plants with 250, 500, 1000, 2000, 4000 and 8000 J2 / plant resulted in
2.3%, 23.3%, 28.4%, 34.7%, 41.0% and 48.4% reduction in plant growth of
lablab bean, respectively. The significant reduction in plant growth was
recorded at and above inoculum level of 500 J2/ plant. Similarly there was a
significant reduction in pod weight at and above the inoculum level of 500
J2 / plant. The reduction in pod weight was 9.6%, 25.0%, 28.7%, 31.2%,
33.9% and 40.1% recorded in the plants inoculated with 250, 500, 1000,
2000, 4000 and 8000 J2 / plant. Nodulation was also significantly reduced
with an increase in inoculum level from 25O-8OOOJ2 as compared to control.
The reduction in nodulation was 4.3 %, 21.7 %, 26 %, 34.8 %, 47.8 % and
65.2 % found in the corresponding inoculums.
The data presented in Table-3.2 showed that the fmal population of
M. javanica was highest in and around the plants inoculated with 8000 J2 /
plant and the lowest population was recorded in and around the plants
inoculated with 250 J2 / plant. A significant linear relationship was found
between the initial inoculum level and the final population of the nematode
47
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i.e. the reproduction factor was significantly reduced with an increase in the
inoculum level from 250-8000 h I plant. The reproduction factor in the
plants inoculated with 250, 500, 1000, 2000, 4000 and 8000 hi plant was
12.0, 11.1, 9.8, 7.5, 4.7 and 3.2, respectively. The number of galls / root
system produced by M. javanica was 24, 47, 58, 76, 130 and 163 recorded
in the corresponding treatments.
4.4 STUDIES ON THE PATHOGENICITY OF MELOIDOGYNE
INCOGNITA ON LABLAB BEAN {DOLICHOS LABLAB VAR.
GLORY):
It is evident from the data presented in Table-4.1 that the rate of
plant growth reduction of lablab bean was directly proportional to the
inoculum level i.e. with increasing in the inoculum levels from 250-8000 J2
/ plant of M incognita, there was increase in the plant growth reduction
except in plants inoculated with 250 J2 / plant where plant growth was
slightly increased as compared to control. The inoculation of plants with
500, 1000,2000,4000 and 8000 Jj/plant resulted in 4.6, 7.8, 25.9, 33.6 and
36.2% reduction in plant growth of lablab beans. The inoculum levels up to
1000 J2 / plant did not show significant reduction in plant growth as
compared to control. However, the significant reduction in plant growth
was recorded at and above the inoculum level of 2000 J2 / plant. Similarly
the significant reduction in pod weight was noticed at and above the
inoculum level of 2000 h I plant. The reduction in pod weight was 2.0 %,
12.2 %, 25.1 %, 28.3 % and 30.5 % in the plants inoculated with 500, 1000,
2000, 4000 and 8000 J2 / plant. Modulation was also significantly reduced
with an increase in inoculum level except 250 h as compared to control.
The reduction in nodulation was 6.8 %, 3.4 %, 24.1 %, 37.9 % and 55.2 %
recorded in the corresponding treatments.
The data presented in Table-4.2 showed that the final population of
M. incognita was highest in and around the plants inoculated with 8000 J2 /
plant and the lowest nematode population was recorded in and around the
48
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"a S3 ^t-3-O
TO 3 O
O
I I Si
o 3
5
S" < 1
o
c <
1
b b
II II p c b b
p p b\ i ' oo 00
» U l
r> a\
oo
§ o
00 00
0 0
ro o o o
u> b
— L/1
o o o
ON ON
0 0 O
•f>^
to
— to o
to o o o
o to
o 00
OS to o o
00
ON U>
o o o
0 0
00
o o o
NO
b
to O N
i I
O O
ON to
- J
00
oo o o
NO
ON
to to
to
o
0 0
to
0 0
-o
to
to
p
U )
o
1
•
1
t
1
3 o o c
3
1 " 3
r to
<
H o * IS
73 re -a o a. B
o" 3 "^ n ^ o
2 3 &3
O
O •a c S" 5' 3
5: c 3 cr -1 o
s.
o o ^^ VI
•-< VI t ^
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3 63 ft-O a n
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g
plants inoculated with 250 J2 / plant. A significant linear relationship was
found between the initial inoculum level and the final population of
nematode i.e. the reproduction factor was significantly reduced with an
increase in the inoculum levels. The reproducfion factor was 10.1, 9.6, 9.0,
8.1, 4.2 and 3.0, recorded in the plants inoculated with 250, 500, 1000,
2000, 4000 and 8000 J2 / plant. The number of galls / root system was 13,
22, 26, 63, 120 and 156 observed in the plants inoculated with
con-esponding inoculum.
The root-knot nematodes infected plants viz. mung bean and lablab
bean at or above threshold level were poor in vigour and showed stunted
growth. Affected plants also exhibit yellowing, premature drying and
shedding of leaves. The drying and shedding of leaves is due to nematode
infestation resulted in lesser number of leaves giving the infected plants an
unhealthy appearance.
The galls were developed on the roots due to nematode infection and
sometimes near by small galls may coalesce to form large galls.
4.5 STUDIES ON THE LIFE CYCLE OF MELOIDOGYNE
INCOGNITA ON MUNG BEAN {VIGNA RADIATA
VAR.JAWAHAR 45):
Penetration of juveniles of Meloidogyne incognita in the roots of
mung bean plants started within 12 hours of inoculation, which increased
gradually with the passage of time till 6 ^ day. It is clear from the Table-5
that on the 6" day of inoculation 88.0% nematodes were found in "A" stage
of maturity and development, whereas on the 8" day only 6.4% nematodes
were in "A" stage and 84.1% in "B" stage. However, on the lO"" day of
inoculation, most of the nematodes were traced in "C" stage (79.5%), only
a few in "B" stage (7.6%) and no nematode was traced on the "A" stage of
maturity and development. On the 13'" day of inoculation, no nematode was
traced in "A" stage, but only a few in "B" stage (2.4%) followed by 8.2% in
"C" stage and 72.2% in "D" stage of development. The nematodes were not
49
Table-5: Studies on the life cycle of Meloidogyne incognita on Vigna radiata var. Jawahar 45.
Davs aft r %age of developmental stages of root-knot nematode
inoculation B C D E Male
6 88.0
8 6.4 84.1 . . . .
10 - 7.6 79.5
13 - 2.4 8.2 72.2
17 - - - 6.1 63.0 3.0
Average number of eggs / egg mass = 190
Females formed (%) = 71.6
Males formed (%) = 3.4
Deposition of gelatinous matrix recorded on = 19''' day
Depositionof eggs in egg masses recorded on = 22"''day
Emergenceof second generation larvae recorded on = 25" day
Number of larvae / kg soil = 9325
traced in A, B and C stages on the 1?"' day of inoculation, but some 6.1% in
"D" stage and 63.0% in "E" stage were observed. Adult males (3.0%) were
also found on 13'*' day of inoculation. Furtrier, out of the total juveniles
(88.0%) that entered the roots, 71.6% developed into females and 3.4% into
males of M incognita. The deposition of gelatinous matrix, deposition of
eggs in egg masses and emergence of second generation juveniles were
observed on 19'^ 22'"', and 25"" day of inoculation, respectively. The total
number of larvae per kg soil and the number of eggs / egg mass was 9325
and 190 respectively.
4.6 STUDIES ON THE LIFE CYCLE OF MELOIDOGYNE
JAVANICA ON MUNG BEAN {VIGNA RADIATA VAR.
JAWAHAR 45):
Penetration of juveniles of Meloidogyne javanica in the roots of
mung bean plants started within 24 hours of inoculation, which increased
gradually with the passage of time till 7''' day. It is clear from the Table-6
that on the 7" day of inoculation 86.2% nematodes were found in "A" stage
of maturity and development, whereas on the 11" day only 2.5% nematodes
were in "A" stage and 79.2% were in "B" stage. However on the 14" day of
inoculation, most of the nematodes were traced in the "C" stage (73.1%),
only a few in "B" stage (5.3%) and no nematode was traced on the "A"
stage of maturity and development. On the 18" day of inoculation, no
nematode was traced in "A" stage, but only a few in "B" stage (1.1%)
followed by 7.9% in "C" stage and 65.0% in "D" stage of development. The
nematodes were not traced in A, B and C stages on the 20" day of
inoculation, but some 3.0% in "D" stage and 60.2% in "E" stage were
observed. Adult males (2.6%) were also found on 20 * day of inoculation.
Further, out of the total larvae (86.2%) that entered the roots, 69.8%
developed into females and 3.0% into males of M. javanica. The deposition
of gelatinous matrix, deposition of eggs in egg masses and emergence of
second generation juveniles were observed on 23' '', 26" , and 28" day of
50
Table-6: Studies on the life cycle of Meloulogyne javanica on Vigna radiata var. Jawahar 45.
Days after
inoculation
%age of developmental stages of root-knot nematode
B D E Male
7
11
14
18
20
86.2
2.5 79.2
D.J
1.1
73.1
7.9 65.0
3.0 60.2 2.6
Average number of eggs / egg mass
Females formed (%)
Males formed (%)
Deposition of gelatinous matrix recorded on
Deposition of eggs in egg masses recorded on
Emergence of second generation larvae recorded on
Number of larvae / kg soil
168
69.8
3.0
23^" day
26'* day
28"' day
12820
inoculation, respectively. The total number of larvae per kg soil and the
number of eggs / egg mass was 12820 and 168 respectively.
4.7 STUDIES ON THE LIFE CYCLE OF MELOIDOGYNE
INCOGNITA ON LABLAB BEAN {DOLICHOS LRBLAB VAR.
GLORY):
Penetration of juveniles of Meloidogyne incognita in the roots of
lablab bean plants started within 24 hours of inoculation, which increased
gradually with the passage of time till ?"' day. It is clear from the Table-7
that on the ?"' day of inoculation 82.3% nematodes were found in "A" stage
of maturity and development, whereas on the 12"' day only 1.9% nematodes
were in "A" stage and 75.5% in "B" stage. However, on the IS"' day of
inoculation, most of the nematodes were traced in the "C" stage (71.2%)),
only a few in "'B" stage (4.6%) and no nematode was traced on the "A"
stage of maturity and development. On the 21^' day of inoculation, no
nematode was traced in "A" stage, but only a few in "B" stage (1.0%)
followed by 6.1%) in "C" stage and 62.3%) in "D" stage of development. The
nematodes were not traced in A, B and C stages on the 25' day of
inoculation, but some 2.4% in "D" stage and 57.9% in "E" stage were
observed. Adult males (2.0%) were found on 25" day of inoculation.
Further, out of the total larvae (82.3%) that entered the roots, 70.3%
developed into females and 2.4% into males of M incognita. The
deposition of gelatinous matrix, deposition of eggs in egg masses and
emergence of second generation juveniles were observed on 28'^ 31^', and
33 day of inoculation, respectively. The total number of larvae per kg soil
and the number of eggs / egg mass was 9310 and 157 respectively.
Table-7: Studies on the life cycle of Meloidogyne incognita on Doiiclws lablab var. Glory.
p. ^. %age of developmental stages of root-knot nematode
'"«*^"'""«" A B C D E Male
7 82.3 . . . - -
12 1.9 75.5 . - - .
18 - 4.6 71.2
21 - 1.0 6.1 62.3
25 - - - 2.4 57.9 2.0
Average number of eggs / egg mass = 157
Females formed (%) = 70.3
Males formed (%) = 2.4
Deposition ofgelatinous matrix recorded on = 28"'day
Deposition of eggs in egg masses recorded on = 31^' day
Emergenceof second generation larvae recorded on = 33' ''day
Number of larvae / kg soil = 9310
4.8 STUDIES ON THE LIFE CYCLE OF MELOIDOGYNE
JAVANICA ON LABLAB BEAN (DOLICHOS LABLAB VAR.
GLORY):
Penetration of juveniles of Meloidogyne javanica in the roots of
lablab bean plants started within 12 hours of inoculation, which increased
gradually with the passage of time till 5"" day. It is clear from the Table-8
that on the S"' day of inoculation 89.4% nematodes were found in "A" stage
of maturity and development, whereas on the 7" day only 6.0% nematodes
were in "A" stage and 81.2% in "B" stage. However, on the 8" day of
inoculation, most of the nematodes were traced in the "'C" stage (78.0%),
only a few in "'B" stage (6.9%) and no nematode was traced on the "A"
stage of maturity and development. On the 11 day of inoculation, no
nematode was traced in "A" stage, but only a few in "B" stage (3.2%)
followed by 7.8% in "C" stage and 73.6% in "D" stage of development. The
nematodes were not traced in A, B and C stages on the 13" day of
inoculation, but some 7.0% in "D" stage and 66.1% in "E" stage were
observed. Adult males (4.3%) were also found on 13" day of inoculation.
Further, out of the total larvae (89.4%) that entered the roots, 73.0%
developed into females and 4.8% into males of M. javanica. The deposition
of gelatinous matrix, deposition of eggs in egg masses and emergence of th th th
second generation juveniles were observed on 16'", 18 , and 20" day of
inoculation, respectively. The total number of larvae per kg soil and the
number of eggs / egg mass 7210 was and 185 respectively.
52
Table-8: Studies on the life cycle oi Meloidogyne javanica on Dolichos lablab var. Glory.
Davs afte %age of developmental stages of root-knot nematode
•"''^"'"*'«" A B " " ^ C D E M ^
5 89.4 . . - - .
7 6.0 81.2 - - - .
8 - 6.9 78.0
11 - 3.2 7.8 73.6
13 - - - 7.0 66.1 4.3
Average number of eggs / egg mass = 185
Females formed (%) = 73
Males formed (%) = 4.8
Deposition of gelatinous matrix recorded on - 16"'day
Deposition of eggs in egg masses recorded on == 18' day
Emergence of second generation larvae recorded on = 20'" day
Number of larvae / kg soil = 7210
<Disctission
CHAPTER-5
DISCUSSION
5.1 PATHOGENICITY OF ROOT-KNOT NEMATODE
(MELOIDOGYNE SPP.) ON MUNG BEAN AND LABLAB
BEAN:
The perusal of data presented in Tables 1.1-2.2, clearly indicates that
the significant reduction in plant growth of mung bean was recorded at an
initial inoculum level of 1000 h of Meloidogyne incognita per plant and
2000 J2 of Meloidogyne javanica per plant, which are therefore considered
as the pathogenic levels of the respective nematodes for mung bean.
Similarly, the data presented in Tables 3.1-4.2, clearly showed that the
significant reduction in plant growth of lablab bean was recorded at an
initial inoculum level of 2000 J2 M. incognita I plant and 500 J2 of M.
javanica I plant that are therefore considered as pathogenic levels of the
root-knot nematodes for lablab bean. Moreover, the yield of both the plants
was also significantly reduced at the pathogenic \QVQ\S of root-knot
nematodes.
It was observed that with the increase in the level of inoculum
resulted in a progressive increase in host infestation as indicated by the
number of galls as well as nematode multiplication. The trend in nematode
multiplication seems to be negatively correlated with the inoculum level of
nematodes. The decrease in nematode multiplication at highest inoculum
level was perhaps due to the destruction of root system and competition for
food and nutrition among the developing nematodes within the root system
and also due to the inability of larvae to find out new infection sites of
subsequent generation (Ogunfowora, 1977). According to Oostenbrink
(1966), the increase in the nematode populations and subsequent reduction
in the yield of crop are directly influenced by thle initial density of the
nematodes in the soil. His view holds true with the present findings wherein
plant growth was proportionately affected with an increase in the initial
inoculum levels of the nematodes. The progressive decrease in the plant
53
growth and nematode multiplication with increasing level of root-knot
nematodes on different crops has also been reported by various workers
from time to time (Raut and Sethi, 1980; Salem and Eissa, 1981; Khan and
Hussain, 1989; Meena and Mishra, 1993; Patel et al, 1996; Dalai and
Bhatti, 1996; Pathak et al. 2000; Khan, 2003; Khan et al, 2004; Kumar
and Pathak, 2005; Khan and Ashraf, 2005; Khan et al, 2006; Khan et
al.,2006).
Tiyagi and Alam (1988) reported that the damaging threshold level
of M incognita on mung bean cv-T44 was 1000 larvae/plant, which is in
agreement with our results. However, on the other hand Samanathan and
Sethi (1996) and Haseeb et al, 2005 reported the inoculum level of 500 J2/
kg soil was pathogenic to mung bean and Dalai and Bhatti, 1996 reported
that 100 h of M. javanica per plant was pathogenic to mung bean. The
pathogenic level of M incognita has also been reported as 2000 J2 / plant by
various workers on different crops (Mani and Sethi 1984; Krishana and
Krishnappa; 1994; and Khan and Ashraf; 2005) that is in agreement with
present results on lablab bean. The results on pathogenicity of M javanica
are not in accordance with the fmdings of Bhat and Krishnappa (1989) on
groundnut. Khan et al, 2004 on cucurbits, Dalai and Bhatti, 1983 on guar
and Khan and Ashraf (2005) on lettuce who reported that 1000 J2 of M
javanica I plant as pathogenic level.
Results obtained on pathogenicity of M. javanica on mung bean are
in agreement with the fmdings of Khan et al. (2004) who reported 2000 J2
oi M. javanica as pathogenic level in bitter gourd. However, the pathogenic
level of M. javanica has been reported as 500 h /kg in black gram
(Srivastava et al, 1979), and 1000 h I plant in broad bean (Gupta and
Paruthi, 1989). The results on pathogenicity of M incognita on lablab bean
are in agreement with the fmdings of Mani and Sethi (1984) on chickpea
who reported 2000 J2 / plant as pathogenic level. Gupta et al (1987)
reported that the inoculum level of 500 J2 of M. javanica was pathogenic to
black gram which is in accordance with our results on lablab bean. It is also
54
reported that the inoculum threshold level of Meloidogyne spp. varied from
0.5-1.0 juveniles per gram of soil in different crops viz. tomato, brinjai okra
cucurbits, radish, turnip, pea and Chinese cabbage (Mangant and Bhatti,
1987 and Bhatti and Wallia, 1992). The variation in the inoculum threshold
level of root-knot nematodes is attributed to cumulative effects of various
ecological and environmental factors influencing the survival and
multiplication of nematodes and due to different hosts used in the studies
(Van Gundy, 1985).
The nematode showed adverse effects on the number of bacterial
nodules, as there was a significant reduction in the number of nodules with
increase in the inoculum levels of nematode. Adverse effects of root-knot
nematodes on bacterial nodulation have also been reported by
Balasubramanium (1971), Meena and Mishra, 1993 and Dalai and Bhatti
(1996) on various pulse crops.
5 . 2 LIFE CYCLE OF ROOT-KNOT NEMATODE (MELOIDOGYNE
S P P . ) ON MUNG BEAN AND LABLAB BEAN:
The results presented in Tables 5 and 6 clearly indicated that root-
knot nematodes viz. M incognita and M. javanica required 25 and 28 days
respectively to complete their life cycles on mung bean. Similarly, the data
presented in Tables 7 and 8 shows that M. incognita and M. javanica
required 33 and 20 days, respectively to complete their life cycles on lablab
bean. The total duration of life cycle of M incognita on different hosts has
been reported by various workers fi-om time to time, i.e. 36 days in eggplant
(Dhawan and Sethi, 1976); 29 days in mung bean and 44 days in guar
(Datta et ai, 1990); 23-25 on tomato, 27 days on okra and 27-30 days on
eggplant (Saxena and Jagpal,1998); 22 days in papaya (Khan, 2002); 27
days on balsam (Khan, 2003) 29 days on Japanese mint (Singh and Kumar,
1998); 32 day in black gram (Mahapatra and Swain, 1999); 32 days on
lettuce (Khan and Ashraf, 2005). Similarly, M. javanica completes its life
cycle within 30 days on carrot (Huang, 1986); 23 daysjm balsam (Khan et
55 'r.'^^r^^^'i'^'^ o.S-> J<^.
al, 2006); 29 days on lettuce (Khan and Ashraf, 2005); 26 days on brinjal
(Ashraf and Khan, 2005); 27 days on broccoli (Khan et al, 2006); 28 days
on brinjal (Ravichandra et al., 1988). The total time taken for completion of
life cycle of Me loidogyne species under optimum conditions (opt. temp. 27-
30°C) as 3-4 weeks Parihar et al. (1998). The variation in time required to
complete the life cycle might be due to a number of ecological factors
especially host status, soil temperatiire, moisture etc. (Wallace, 1973;
Swarup and Dasgupta, 1986, Bhatti and Walia, 1992).
56
Summary
ConcCusion
CHAPTER-6
SUMMARY AND CONCLUSION
Pulse crops occupy an important position in Indian Agriculture and
constitute major source of protein to the large number of vegetarian
population of country. The root-knot nematode {Meloidogyne spp.) is an
important group of plant parasitic nematodes, most damaging and posing
threat to pulse crops. The present studies carried out on the pathogenic
potential and life cycle of root-knot nematodes {Meloidogyne spp.) on beans
revealed the following:
1. The pathogenic potential Of M incognita and M.javanica on mung
bean are 2000 and 1000 J2/plant, respectively.
2. The pathogenic potential of M. incognita and M javanica on lablab
bean are 2000 and 500 J2/ plant, respectively.
3. The root-knot nematodes, M. incognita and M javanica required 25 and
28 days to complete their life cycle on mung bean, respectively.
4. The root-knot nematodes, M incognita and M. Javanica required 33 and
20 days to complete their life cycle on lablab bean, respectively.
It can be concluded from the present studies that root-knot
nematodes are important pests of mung bean and lablab bean and need
effective measures for their control. Moreover, the information acquired
from the present study may provide a baseline for further research to
develop appropriate and effective management tactics.
CHAPTER-7
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