By:MOHAMMAD SAFAR ALIZADAH NOORI

HYBRID SEED PRODUCTION

TECHNOLOGY OF MAIZE

Scientific name : Zea mays and Family : Poaceae

Maize (Zea mays) is one of the most important cereal crop in the world grown over an area of 132 Mha with a production of 570m.t. It is the crop with the highest productivity.

Maize is serving as staple food for vulnerable segment of the population and it rank first in importance as feed crop and also important source of raw material used in numerous industrial materials.

Introduction

Dent corn : It is characterized by a depression or dent in the crown of the seed. The starch at the sides of the seeds is corneous while the soft starch extends to the narrow base or tipFlint corn: The seeds of flint maize are hard and smooth and contain little soft starchSweet corn: Contain is sweetish starch and is characterize by a translucent, horney appearance when immature, and a wrinkled condition when dry.

Classification maize kernels

Flour corn: Flour soft maize as kernels , which are compose entirely of soft starchPop corn: The grains unusually small pointed and contain an even higher per cent of hard starch than flint maizePod maize: It is an unusual type of maize each kernel of which enclosed within the lemma and palea which are well developWaxy maize: Waxy maize is so named because of the some what waxy appearance of the kernels

Floral biologyThe monoecious corn

plant has female flowers that develop on the side of the plant and emerge from the leaf node.

The inflorescence is unisexual and monoecious.

Staminate inflorescence is terminal and known as tassel and pistillate is axillary and called as cob

Anthesis and PollinationMaize is an example for protandry. Pollen shedding begins 1-3 days before the silks

emerge from the cob. It is estimated that a normal tassel produces

2,50,00,000 pollen grains. Pollen is viable for 12-18 hours. Silk remains receptive

for 8-10 days.Anthesis continues up to 2 weeks

a. HYBRIDS b. Open pollinated varietiesc. Synthetics d. Composites

Hybrid seed production

Hybrid seed of maize may generally be produced from following different cross combinations

Single cross hybrid: (AXB) e.g. DMH-2(CI-4 X KDMI-10) NAH-2049(147-F2#89 X MAI-105) (Nithyashree)Double cross : (AXB) X (CXD)e.g. Deccan (CM 104 x CM 105) x (CM 202 x CM 201) Ganga-1 (CM 101 x CM 102) x (CM 200 x CM 202) Three way cross: (AXB) X C e.g. Ganga -5 (CM 202 x CM 111) x CM 500Double top cross : (AXB) X Compositee.g. Ganga safed, Histarch, Ganga 4.

Factors affecting hybrid maize seed production

• Planting ratio• Non-synchronization of flowering• Genetic drift• Detasseling• Mechanical admixtures• Rouging• Physiological maturity of the crop• Harvest seed crop• Post harvest operation

Planting ratio :

Maize hybrids vary considerably in respect of plant height, Panicle size, the amount of pollen produced and duration of pollen availability.

Single cross hybrid : 4:2 Double cross : 6:2Three way cross: 6:2 Non-synchronization of flowering: Good seed set in seed parent can be achieved by chronological

adjustment of pollen shedding and silking respectively.

Prolongation of effective flowering period, planting design, efficient alteration of rows planting ratio, staggered planting are some of measures which are effectively used to ensure maximum synchronization and good seed set.

Genetic drift: It is recognised as a important factor affecting quality of seed.

The danger of genetic change in respect of cross pollinated crops like maize is prominent.

Detasselling: Removal of male inflorescence from the monoecious crop. The time taken for shedding of pollen from the tassel in 1-2 days after emergence. Hence the tassel should be removed before the shedding of pollen.

Precautions to be taken while detasseling Hold the stem below the boot leaf in left hand and the base of the tassel in right hand and pull it in a single pull.

No part should be left on the plant as it causes contamination.

It should be uniform process done daily in the morning in a particular direction.

Donot break the top leaves as the field may be reduced due to the earning of source material to accumulate in sink (seed) as removal of one leaf course 1.5% loss 2 leaves 5.9% loss and three leaves 14% loss in yield.

Detassel only after the entire tassel has come out and immature detasseling may lead to reduced yield and contamination.

Mark the male rows with marker to avoid mistake in detasseling.Look out for shedders (shedding tassel) in female rows as they may

cause contamination.

After pulling out the tassel drop it there itself and buried in soil. Otherwise late emerging pollen from detasseled tassel may cause contamination.

Donot carry the tassel through the field as any fall of pollen may lead to contamination.

Donot practice, improper, immature and incomplete detasseling. Improper detasseling: a portion of the tassel is remaining in the plant

while detasseling.

Immature detasseling: carrying out detasseling work when the tassel is within the leaves.

Incomplete detasseling: the tassel is remaining in lower or unseen or unaccounted in within the whole of leaves.

Shedding tassel: either full or part of tassel remain in female line after detasseling and shedding pollen which may contaminate the genetic purity of the crop.

Contd…..

Mechanical admixtures: These can be avoided taking due precaution at harvesting, seed setting, bagging and storing operations etc.

Rouging: Based on distinct and diagnostic characters furnished by the breeder, rouging has to be performed in seedling stage flowering stage and at the time of harvesting (Plant and Ear Characters).

Physiological maturity of the crop: The crop should be harvested at proper stage of maturity to minimize qualitative & quantitative losses. The symptoms of physiological maturity are the degeneration, formation of dunken layer, moisture content of seed 35% and cob sheath turn straw yellow colour.

Harvest seed crop: the seed crop should be harvested when moisture content falls to 20-25% and harvest the male row first and remove from the field and then harvest the female rows.

POST HARVEST OPERATION :

Cobs sorting: Remove sheath and check for kernel colour, shank colour , disease cobs, kernel arrangement etc.

Shelling : moisture content 15 % and mechanical cob shellers and also manual rubbing against stone are used.

Improper shelling leads to 48 % damage to kernel, growth of storage fungi and also pericarp damage, to identify the pericarp damage a crack on the pericarp and also by ferrichloride test or Tz test.

Seed production technology

Maize is grown in wide range of climatic conditions.

About 85% of the total acreage under maize is grown during monsoon because of the fact that the crop stops growing if the night temperature falls below 15.60 C or 600 F.

Maize crop needs more than 50% of its total water requirements in about 30 to 35 days after tasseling and inadequate soil moisture at seed filling stage results in a poor yield of shriveled seeds.

Maize needs bright sunny days for its accelerated photosynthetic activity and rapid growth of plants.

Prolonged cloudy period is harmful for the crop but an intermittent sunlight and cloud of rain is the most ideal for its growth.

Climate

Deep fertile soils rich in organic matter

well-drained soils are the most preferred ones however maize can be grown on variety of soils.

Soil should be medium textured with good water holding capacity.

The pH should be between 6.5 to 7.

Soil

Seed source

Certified or foundation seeds are to be procured from the approved certified agencies

A plant population density of 50-55 thousands/ha is ideal to attain maximum yield.

Hybrids: Female 10kg/ha Male 4 kg/ha

Spacing : 60 - 75cm row spacing and plant to plant 25 -30cm.

Seed rate and Spacing

FYM / compost: 8-10 t /ha

NPK: 200:100:100kg /ha

Micronutrients : If deficiency is found, apply 20 kg of zinc sulphate / ha , boron @ 5kg /ha and Fe @12.5 kg/ha

Manures, Fertilizers and Micro nutrients

Table 1: Plant height, number of days taken for 50% flowering and number of barren plants (without cob) as influenced by spacing and fertilizer levels in African tall fodder maize.

Treatments Plant height (cm) No. days taken for

50% flowering

No. barren

plants

Seed yield

(q/ha)

Spacings (cm)

S1: 45X30 208.63 63.11 15 25.35

S2:45X45 208.101 62.22 8.50 28.93

S3:60X30 206.97 62.77 1.44 39.48

S4:60X45 214.52 62.25 0.22 47.55

S5:75X30 209.93 62.77 0.22 51.67

S6:75X45 210.28 62.55 0.00 53.27

SEm± 3.91 0.30 0.28 0.19

CD at 5% NS NS 0.79 0.62

Fertilizer levels

F1:100:50:25 202.74 64.11 4.83 39.38

F2:150:75:50 208.90 62.50 4.11 41.22

F3:200:100:75 215.04 61.38 3.77 42.55

SEm± 2.75 0.21 0.20 0.13

CD at 5% 7.66 0.59 0.56 0.37Channakeshava B.C (1998)

Sowing depth (3-5cm) must be uniform to get a uniform emergence. The planting may be done as follows1. Planting on the ridge2. Planting in furrows3. Planting on flat bed with no earthing up4. Planting on flat bed.

Earthing up after 40-45 days of days of planting

Methods of planting and Earthingup

Isolation DistanceField standards for isolation

Same kernel colour 400m

Different kernel colour 600m

Same inbred not confirming to varietal purity 400mFor Foundation single crosses and hybrid of certified class

 Particulars Foundation seed (m)

Certified seed (m)

Same kernel colour 400 200

Different kernel colour 600 300

Field of single cross not confirming to varietal purity 400 200

Single cross with same male parent confirming to

varietal purity 5 5

Single cross with other male parent not confirming to

varietal purity 400 200

Isolation distance depends on seed yield of the lines and size of the plot.

The required minimum isolation distance is 200 m in certified seed production from the contaminant source.

Four pollen parent border rows in the field is to be inspected four ha or less in size.

The isolation distance may be decreased by 5 m for each increment in 2 ha in size of the plot to a maximum of 16 ha.

Here the isolation distance may be further decreased by 12.5 m for each additional border rows to a maximum of 16 pollen parent border rows.

Isolation distance

Borders rows must be planted in the seed field or adjacent to it, but in no case separated by more than five meters from the field.

Borders rows must be planted all along and opposite to the contaminating maize.

There should be a reasonable stand of border row, i.e., there must not be gapes in the border rows. Border rows must have been planted using the seed rate and spacing adopted for the seed crop.

The area planted under the border rows is taken into consideration while modifying the isolation distance.

Border rows

Contd..

natural barriers such as tall thick trees, buildings…etc between in the seed and contaminating fields shall not be a substitute to border rows.

Border rows must be planted with seed used for planting male rows in the seed field. Seed saved from male rows of the previous production of the same cross can not be used for planting of border or for planting with isolation distance.

It is the process of removal of voluntary plants, off-types, other crop plants, pollen shedders, and objectionable weed plants from the seed field before either of the crops comes to flowering.

Rouging:

First inspection: The field should be inspected to verify that it is properly isolated and free of volunteer plants.

Second inspection: During the vegetative growth phase. Isolation should be checked, along with the presence of disease, insect pests, or weed infestations. At this stage, off-type and disease plants may be rouged.

Third inspection: made just prior to and during flowering. At this time the maize seed field is most susceptible to genetic contamination from windblown pollen coming from off-type plants within the field or other maize varieties in surrounding fields.

Plants that are off-type or diseased, along with harmful weeds, must be removed at this time. Fourth inspection : A pre-harvest or harvest inspection may be conducted as the crop reaches maturity and the seed has lost a significant portion of its moisture content.

Field Inspections

It has been estimated that the maize crop requires about 50 per cent of its total water requirement in a short period of 30-35 days after tasselling.

The most critical stage of irrigation during crop growth is during flowering and post-flowering particularly during the grain-filling period.

Two to three weeding may be necessary, following which the crop is earthed up to provide for better standability.

No weeding is required after earthing up. Effective weed control can be obtained by spraying Simazine or Atrazine (@ 1-1.25 kg/ha of 50% W.P.) before the crop germinates.

Irrigation

Weeding:

Brown stripe downy mildew, Polysora rust, Tropical rust, Black kernel rot, Maize mosaic virus I (MMV), Turcicum leaf blight, Common smut and Head smut.

Shoot fly and cob borer are the important insects. Control measures: Spray Mancozeb 2.5g/lit or Dithane M-45 spray

can be taken (0.4%) as soon as first symptoms are observed and it can be repeated at 10 days interval till flowering.

Hybrids like Deccan, Ganga-5, Deccan Hybrid Makka-103 and DHM - 1 which are resistant to rot disease to minimize the disease intensity

Pests and Diseases

Harvesting: Harvest when the husk completely turns into straw colour.

Methods of harvesting: Male lines are harvested first followed by female lines.

Threshing:Dehusking - The husks are removed manually, Cob sorting - Remove non filled, diseased cobs and cobs having kernel colour variation.

Shelling: The cobs are shelled either mechanically or manually at 15-18% moisture content.

Drying: Seeds are dried to 12% moisture content.

Grading: Grade the seeds using 18/64" (7.28 mm) sieve.Seed treatment: Treat the seeds either with captan or thiram 75% W.P. @ 70 g/100 kg.

Yield: 2.5 to 3.6 tonnes / ha

Seeds stored in high density polythene bag (700 gauge) and poly lined gunny bag with reduced moisture of 8 per cent retained seed quality parameters upto 15 months compared to seeds stored in cloth bag and gunny bag.

Storage

Field standards

Particulars FS CS

Off types 0.2 0.5

Shedding tassel 0.5 1.0 (when receptive silk is 5% or more)

Seed standards for hybrids:Parameters Foundation seed Certified seed

Physical purity (%) (min) 98 98

Inert matter (%) (max) 2 2

Other crop seed (max) 5 kg-1 10 kg-1

ODV seeds (max) 5 kg-1 10 kg-1

Germination % (min) 80 90

Moisture content (%) (max)

a. Moisture pervious 12 12

b. Moisture vapour proof 8 8

Requirements

Substrata Between paper

Temperature 20-30oc

First count 4

Final count 7

Moisture determination Temperature

By oven method1300

Drying time 4 hrs

Grinding Fine grinding

Standards for Germination test

THANK YOU….