Hybrid maize is produced by cross-pollinating two unrelated male and female plants of different inbred lines. By nature of the maize plant having separate male and female flowers, the tassel and cob

The characteristics of hybrid maizeIt is uniform in appearanceIt has vigor (makes them more competitive with weeds)It is high yielding.It is selected for improved grain quality.A particular hybrid can be selected for specific pest and disease resistance or drought tolerance.

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.Staminateinflorescence 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

Hybrids Open pollinated varieties Synthetics Composites

Introduction Scientific name :Zeamays

Family :PoaceaeMaize (Zeamays) 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.

Hybrid seed production Hybrid seed of maize may generally be produced from following different cross combinationsSingle 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 Ce.g. Ganga -5 (CM 202 x CM 111) x CM 500Double top cross : (AXB) X Compositee.g. Ganga safed, Histarch, Ganga 4.

Crosses between males and females can be made in four different ways to give rise to different kinds of hybrids:Single-cross hybrids – This is when two unrelated inbred parents are crossed.Three-way hybrids – Three parents are involved in a three-way cross. The female of a three-way hybrid is a single-cross hybrid, while the male is an inbred line.Double-cross hybrids – In this cross, both parents are single-cross hybrids.Top-cross – In this case, one of the parents is an open-pollinated variety and the other is a single-cross hybrid or an inbred line.

Factors affecting hybrid maize seed productionPlanting ratioNon-synchronization of floweringGenetic driftDetasselingMechanical admixturesRouging Physiological maturity of the cropHarvest 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: 6:2Non-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.

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.

Rouging: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.

Manures, Fertilizers and Micro nutrientsFYM / compost: 8-10 t /haNPK: 200:100:100kg /haMicronutrients : If deficiency is found, apply 20 kg of zinc sulphate / ha , boron @ 5kg /ha and Fe @12.5 kg/ha

ClimateMaize 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.

SoilDeep fertile soils rich in organic matterwell-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.

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

Seed rate and SpacingA plant population density of 50-55 thousands/ha is ideal to attain maximum yield.Hybrids: Female 10kg/ha Male 4 kg/haSpacing : 60 - 75cm row spacing and plant to plant 25 -30cm.

Methods of planting and EarthingupSowing depth (3-5cm) must be uniform to get a uniform emergence. The planting may be done as followsPlanting on the ridgePlanting in furrowsPlanting on flat bed with no earthing upPlanting on flat bed.Earthing up after 40-45 days of days of planting

Weeding: 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. IrrigationIt 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.

Pests and DiseasesBrown 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

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

StorageSeeds 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.

The advantages of growing hybrid maize:Hybrids are generally higher yielding than open-pollinated varieties, if grown under suitable conditions.Hybrids are uniform in color, maturity, and other plant characteristics, which enables farmer to carry out certain operations, such as harvesting at the same time.The uniformity of the grain harvested from hybrids can also have marketing advantages when sold to buyers with strict quality standards.

The disadvantages of growing hybrid maizeHybrid seed is more expensive than open-pollinated maize seed.The farmer needs to have more than 2 t/ha in order to justify the cost of the seed. Farmers situated in a low potential environment and who cannot afford extra inputs such as fertilizer will not recover the costs of the hybrid seed.Fresh hybrid seed needs to be bought every planting season.The grain from a crop grown with hybrid seed should not be used for seed. The farmer cannot replant grain as seed without major reductions in yield, which might be a decrease of 30 % or more.The farmer might not always be able to source new seed in time for the planting season.