Maize

Varietal And Hybrid Seed Production

Introduction

• The first coordinated crop improvement project was launched on maize by ICAR in 1957. Large number of inbred lines and hybrids were introduced from USA and corn belt region.
• These inbred lines along side with exotic and indigenous hybrids were tried in multilocational trials.
• As a result 28 inbreds were picked up for utilization in hybrid development.
• Some exotic hybrids particularly from Southern USA (NC 27, Texas 26 and Dixie 18) displayed significantly higher yield but were not accepted by the Indian farmers due to their dent type grain.
• These dent type hybrids also had a problem in seed production, as their parental lines were adapted to temperate climate.
• Realizing these difficulties, Indian germplasm collection was intensified.
• The local land races collected were yellow flint grain type, obviously preferred by Indian farmers.
• After characterisation and classification of Indian land races and simultaneous effects for extracting inbred lines both from indigenous and exotic materials, first set of yellow double cross hybrids were released in 1961 (Ganga 1, Ganga 101, Deccan and Ranjit).
• Though these hybrids performed very well in the farmers fields, success was limited by the problem encountered in their economic seed production.
• To tie this problem a short-term approach odd developing non-conventional hybrids (Double top cross hybrids and hybrids involving early generation inbreds) was immediately adopted.
• As a result in 1963 two double top cross hybrids ( Histarch, ganga-safed-2) were released.
• Also, composites and synthetic population were synthesized with the objectives of raising the levels of base population for developing agronomically better inbreds and for the commercial cultivation.
• Presently over 20 hybrids ( Including double cross, double top cross and three way cross ) besides many composites and synthetics are released to the farmer for their commercial exploitation.
• Kisan, Jawahar, Sona, Vijaya, Amber and vikram were released in 1967. Vijay become popular not only in India but also in neighbouring countries like Pakistan and Nepal.
• To enhance the performance of composite varieties by accumulating favorable alle Intra-population improvement programme at the national level was initiated in ten elite composites of various maturity groups.
• Five broad based gene pools in two grain colours yellow and white ( AB yellow, AB white , BC yellow, CD yellow, CD white) were constituted to develop promising varieties and hybrids.

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Steps Involved In Hybrid Seed Production

• Breeders have developed high yielding varieties or hybrids of maize. Those improved stains have made a major contribution to increased food grain production.
• Maize hybrids are more attractive to seed industry for the economic reasons namely, higher profit margin for seed producers and farmer must return to buy new hybrid seed each year.
• Use of hybrid maize has resulted in the development of a new enterprise the production, processing sale and distribution of Hybrid seed.
• Thus the seed production today is a specialized and essential industry. It is analogous to fertilizer or pesticide industry.
• The seed industry is made up of several components including research production, quality control and marketing.
• Production of high quality seed is the primary objective of a seed programme.
• Care is to be taken to fix certification standards for various stages of seed multiplication to produce quality seed with out hampering seed production.
• When an improved strain is developed and performs well enough for use by the cultivators, it is proposed for release.
• The plant breeder provides its specific genetical and morphological characters based on which the cultivar is identified.

Maize Hybrid seed production consists of three stages. They are:

• Breeder seed.
• Foundation seed.
• Certified seed.

Breeder Seed

• Production of breeder seed is directly controlled by the plant Breeder.
• This stage of seed production is called "Breeders seed".
• It is generally produced in limited area either by hand pollination or in isolation.

Foundation seed

• Foundation seed generally consists of production of single crosses by sowing male and female parents.
• These parents will be sown in 2:4 row ratio.
• Destasselling will be done in female rows.
• All off types, diseased and rogues if any found will be removed.
• Certification standards will be maintained under the guidance of monitoring team consisting of National seed corporation agencies, Certification, Agencies, Breeders and I.C.A.R. Nominee.

Certified seed

• Certified seed i.e. the last stage of Maize hybrid seed production.
• Male and female single crosses are generally sown on 2:6 ratio.
• Female plants are detasseled.
• All off types, diseased and rogues if any found will be removed.
• Certification standards will be maintained under the guidance of monitoring team. The seed obtained on female rows is called certified seed.
• This seed is labeled as hybrid seed and sold to the farmers for commercial cultivation.

DHM 105 Doble cross hybrid production

Breeder seed	CM 119CM 120CM 211CM 131
Foundation seed	CM 119 X CM 120CM 211 X CM 131
Certified seed	(CM 119 X CM 120) X (CM 211 X CM 131)
DHM 105

Trishulatha Three way cross Hybrid production

Breeder seed	CM 131CM 211CM 120
Foundation seed	CM 131 X CM 211
Certified seed	(CM 131 X CM 211) X CM 120
Trishulatha

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Factors Affecting Maize Seed Production

Planting ratio

• At present uniform planting ratio of 2:4 for foundation seed production and 2:6 for certified seed production plots has been recommended.
• Maize inbreds vary considerably in respect of plant height, Panicle size, the amount of pollen produced and duration of pollen availability.
• Some time this factor may pose some problem to the producers.

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 synchronisation 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.
• Plants of different types permitted in a line may be susceptible to selection resulting in complete shift in the average perform and of a line over a period of time if produced repeatedly in smaller plots.

Detasseling

• All tassles must be removed from the female rows before they have shed any pollen. Pulling the tassels usually as soon as they are well out of the boot is the most satisfactory method of removal.

Mutation

• Aging of seed under storage is reported to have increased frequencies of chromosomal aberrations and point mutation.

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 minimise qualitative & quantitative losses.

Seed size

• Grading of seed is important as it avoids smaller seed, under developed and damaged seeds.
• Smaller seeds had good germination but under stress condition the performance was significantly effected.

Storage

• Proper care for aeration temperature and humidity etc. should be taken from time to time.

Limit for breeder seed indent

• Large indents of breeder seeds are not being entertained from the seed producing agencies.
• As there is a provision for stage I and stage II line increase, no producer should be permitted to indent more than 4 to 5 kg per inbred in a year.
• If the total indent for a inbred comes to 30 to 40 kg per year, it will be possible for the breeder to multiply a quintal or two of each inbred and store them so that he does not have to multiply them in large quantities every year.
• This will also ensure against the possibility of gene shift due to the frequent multiplication of any inbred.

Hybrid maize seed production

• (Every stage of seed production is carried out in isolation).

Stage of seed Productions	Particulars	Remarks
1. Breeders seed	Parental lines are increased in limited area	Parents should have genetic purity and certifying standards.
2. Foundation seed	Male and Female parents are geneally sown in 2:4 ratio. The seed obtained on female rows is called foundation seed	Detasseling should be attended in all female Plants at proper time parents should have genetic purity and Certifying standards.
3. Certified seed	Male and Female single crosses are generally sown in 2:6 ratio. The seed obtained on female parent is called certified Seed or Hybrid seed.	Detasseling should be attended in all female plants at proper time Both single crosses (Male & Female) should posses genetic purity and certifying standards.

Seed Standards in maize

Parameters	Breeder Seed	Foundation Seed	Certified Seed
Pure seed minimum	100	98.0	98.0
Insert matter	None	2.0	2.0
Weed seed	None	None	None
Other crop seed	None	0.2	0.2
Germination capacity Minimum)	98.0	90.0	90.0

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Limitations Of Hybrids

• Varieties with superior performance can be produced at each cycle of development as opposed to the substantial time log required for hybrid development .
• Since base populations and varieties improve proportionally with each selection cycle, after a given number of cycles there is very little difference in the expected performance of hybrids varieties.
• In fact it pays if adequate selected is practiced in each cycle, varieties can be superior to hybrid performance after any fixed period of time.
• To obtain anticipated potential yield of hybrids, new seed must be obtained each season from a specific source.
• However, the lack of an appropriate infrastructure for seed production and distribution in many developing nations make the use of hybrids a more difficult proposition.
• In contrast the relatively easy reproducibility of varieties makes such material more appropriate in these nations.
• In the event of poor quality or untimely seed distribution by the not so well organized seed corporation, the farmers themselves can save their variety seed for the next planting and even subsequent seasons if necessary.
• Farmer to farmer distributions of seed is possible if varieties sown by them are with desirable isolation distances. Seed increase is also more rapid than with hybrids.
• Costs lower in seed production of varieties since it requires only on isolation while in case of hybrids they need 5 to 7 isolations and cost of production is more.
• Varieties can be served as base material to develop parental lines and also can be used as a male parent in making double top cross hybrid.
• Varieties are more stable than hybrids in areas of varying rainfall and high soil variability.
• They are recommended for adverse conditions. Since they have broad genetic base in their makeup.
• Desirable attributes say resistance to a disease can be introgressed in the varieties very conveniently.

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Current Status Of Hybrid Development

• The strengthening of hybrid research in 1989 under the special project on Promotion of Research and Development of Hybrids in Selected Crops has taken care of many important issues like early maturing kharif hybrids with emphasis on their suitability to tribal areas
• Cold-tolerant full season hybrids for rabi season for north-west plains
• Hybrids for rabi cultivation for northeast plains,
• Full season hybrids for both kharif and rabi for peninsular India,
• Development of homozygous inbred lines through haploidy.
• The gaps in seed technology research including production of nucleus and breeder seed, and on-farm research and testing on of hybrids, is also being addressed to.
• A coordinated emphasis on these aspects during the last four years has yielded encouraging results.
• Three-way hybrids, like Trishulata, DHM 105, DHM 107 and DHM 109 have already been released for commercial cultivation during 1991-93.
• A single cross hybrid, JH 1121, with about 35 per cent higher grain yield, low ear placement and resistance to post-flowering stalk rot, is found promising for kharif season in the Indo-gangetic plain.
• The exercise in development of inbreds for both kharif and rabi seasons has led to identification of about 25 promising advance stage inbreds with yield potential from 13.3 to 44.0 q/ha. Out of these, about 15 inbreds have yield potential of over 30.0 q/ha.
• On-farm demonstrations in Andhra Pradesh with DHM 105 and DHM 105 and DHM 107 conducted during kharif 1993 under rainfed situation gave grains yields upto 77 and 69 q/ha respectively, with no pest and disease hazards in both the cases.

Single Cross Hybrids Programme-A thrust area for future

• Maize breeding has gone through many phases and the importance of single cross hybrids has been re-discovered. Nowadays, the emphasis has swung to the development of vigorous inbred lines that have good performance per se and in cross combinations.
• Single cross breeding is also much more effective in terms of time and cost involved.
• Some short cuts can be made in single cross breeding and many of them can be easily integrated with population improvement.
• The practical superiority of single cross breeding in terms of higher gain has been demonstrated in various countries in which maize breeding has evolved.
• Seed production can also be better-planned and easily handled in single crosses in comparison to the multi-parent crosses.
• Adoption of single cross hybrid programme on a large scale in India is bound to accelerate the productivity trend. New high yielding inbreds developed under the programme will greatly help in this direction.

Collaborative Research Projects

Since 1989, six ICAR-CIMMYT collaborative projects in various facets of maize improvement have been in operation. These are :

• Genetic resource exploration, cataloguing and conservation.
• Evaluation of inbred lines for more productive hybrids.
• Cultivation of maize under excess soil moisture and drought conditions.
• Economic studies on maize development.
• Genetic improvement of gene pools for Turcicum leaf blight and sorghum downy mildew resistance.
• Multiple insect resistance and development of borer resistant maize germplasm in south and east Asia.
• Hopefully, in the years to come, some good materials possessing tolerance to important biotic and abiotic stresses would be on the ground.
• Under these projects, stress is contemplated to be laid on banded leaf sheath blight and post flowering stalk rot, which are of economic importance not only in India but also in other Asian countries.

Prospects for maize development in India

• The maize prospects have to be looked from a wider angle and also in cognisance other crops in India as well as status of maize in the neighboring countries.
• Presently India is far behind China, where national average productivity is about 4.5 t/ha. But China is endowed with large maize areas in temperature climate. Which is a fortunate situations compared to India.
• But India is definitely in a better position compared to other countries in the region.
• Quality seed production of new improved cultivars and their popularization is still a grey area in India.
• Since many hybrids with realizable yield potential of around 5 t/ha are already available, the country can easily hope for achieving at least 3.5 t/ha productivity (which is twice the present) in the next 5 to 10 years provided basic issued related with hybrid seed production and popularization could be attend to.
• Maize improvement programme in the country is particularly weak for drought/water logging affected areas in the states of Rajasthan, Gujarat, Madhya Pradesh and Uttar Pradesh, which occupy 55 percent of the total maize area in the country.
• A few options in terms of new hybrids and a number of composites for these areas are available and greater emphasis on transfer of improved technologies is considered essential.
• This alone can substantially increase production/productivity form this major belt as even private sector is not expected to provide greater thrust for such difficult conditions for obvious reasons.
• For other areas in both north and south India, an intensive maize popularization programme duly supported by appropriate incentives is equally essential for large gains in production.
• Obviously, progress in development of single cross hybrids would yield quick results, but a greater emphasis on basic and strategic researches would only provide the needed support for this improvement activity.
• The endeavor should be to have a long term perspective planning for attaining the highest genetic potential possible.
• For this purpose, there is need to identify gene(s) which will increase the genetic efficiency of a new maize plant in utilizing nutrients, especially nitrogen, and their efficient partitioning in the grain, increasing the genetic potential for response to high plant density, and increasing the desirable chemical component of maize to improve its value in various industrial uses.
• For winter maize, the efforts for judicious and systematic introgression of temperature germplasm in tropical maize has to be strengthened to significantly increase rabi maize area.
• Regarding breeding for early maturity, an important objective, there is need to understand the physiological and genetic basis of earliness and to investigate the ways and means to break the linkage, or at least reduce the adverse effects of earliness on grain yield.
• There is also need to take up studies on economic threshold injury by pests and diseases, durable resistance and integrated pest management for developing appropriate technologies with judicious use of chemical fertilizers and pesticides for making possible the adoption of maize-based cropping systems.
• Serious attention is also required to better understand abiotic stresses and the integrated stress management systems to increase maize productivity.
• Any long term strategy will not be complete unless the area of cultivar development for specialized uses is given specific attention to cater the industrial requirements.
• Cultivars suitable for industrial purposes have tremendous significance in not only boosting the yields and improving the economics for farmers and corn million industry, but also for earning valuable foreign exchange.
• Some important areas are high oil content (upto 7%) with maximum concentration of oil in germ portion for easy recoverability, waxy maize (high amylopectin) for starch industry and baby corn for domestic consumption and export.

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Seed Production of Composites

• Farmers using composites can save their own seed for the following year. Care should, be taken that the seed fields have

  1. Adequate isolation of 300 m
  2. Seed from atleast 500-1000 plants is bulked to represent the population.
  3. Select the best plants and not ears

Opaque -2 maize composites

e.g.: Shakti, Ratan and Projina

• Opaque composites are very rich in the essential amino acids particularly Lysine and Tryptophan.
• The genetic make up of these material necessiates the cultivation of the composites in isolation from normal maize. Any contamination of opaque-2 will be apparent in the form of normal transparent kernals in contrast to the dull marble look appearance of opaque-2
• An isolation distance of 300-400 m is adequate. With increase in the number of border rows, the isolation distance can be suitably reduced. Even in the absence of isolation the farmers planting 2-4 ha can save the seed from middle of the field.

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