Cereals

Paddy - Hybrid

Seed Production Of Hybrid Rice

The successful development and use of hybrid rice technology in china during 1970's led the way for development and release of rice hybrid varieties elsewhere. India has made good progress in this regard and it is expected that hybrid varieties of rice shall be soon available for cultivation to the Indian farmers.

Methods of Hybrid-seed production

Hybrid-rice can be produced in the following ways.

  • Three-line system
    The hybrid seed production involves multiplication of cytoplasmic-genetic male sterile line(A line), maintainer line (B line) and a restorer line (R line); and production of F1 hybrid seed (AxR)
  • Two-line system
    The hybrid seed production involves the use of photo-period sensitive genetic male steriles(PSMS). Any normal line can serve as a restorer.
  • By using chemical emasculators
    Chemicals that can sterilize the stamen, with little or no effect on the normal functioning of the pistil, can be used to emasculate female parents for hybrid rice production. The advantages are obvious, no special development of male sterile or restorer lines is required, and extensive varietal resources are available. Chemical emasculators such as male gametocie 1(MF1) and male gametocie 2(MG2) were developed inChina and have been successfully used in hybrid rice production. In chemical emascultion, physiological male sterility is artificially created by spraying the rice plant with chemicals to induce stamen sterility without harming the pistil. In hybrid seed production, two varieties are planted in alternate strips, and one is chemically sterilized and pollinated by the other.

HYBRID-RICE SEED PRODUCTION TECHNOLOGY(THREE LINE SYSTEM)

In the years to come location-specific specialized seed production technology for the released/commercial hybrids would have to be developed for obtaining maximum seed yields and ensuring good seed quality. Good crop management is necessary for raising a hybrid-rice seed production crop. Hybrid-rice production technology described below may be used as a guideline.

  • Choice of areas and Growing season for seed production: the areas ofseed production should be chosen so as to provide the best possible conditions at flowering and the pollen shedding period. The most suitable conditions are, 24-28 C day light average temperature, the relative humidity 70-80 per cent, the temperature difference between day and night 8-10 C and good sunshine. An average day temperature of more than 30 C or less than 23 C, continuous rains, or strong wind are generally harmful to flowering, pollination and cross fertilization. As a rule, in high temperature with low humidity or in low temperature with high humidity some glumes will not open. This lowers the seed yields. The growing of hybrid seed crop should be so adjusted that flowering takes place after the end of high temperature period, but before the start of low temperature period.
  • Selection of seed fields
    The selection of prime field plots is necessary. The seed fields should be free of volunteer plants, well leveled, should have fertile soil with good physical and chemical characteristics, and well drained.
  • Isolation
    the hybrid paddy fields should be isolated from the other paddy fields, including commercial hybrid of same variety; and same hybrid not conforming to varietal purity requirements for certification at least by 200 meters for foundation seed class (A, B & R line production) and by 100 meters for hybrid seed production (AxR Production)
  • Brief Cultural Practices for hybrid (AxR) production Nursery. Raising of vigourous seedlings is an important factor for obtaining high seed yields. The root system of vigorous seedlings are flourishing , leaf sheaths have high carbon content and all this contributes to produce green growth and tillering at the lower nodes so that more panicles and a high seed setting rate per panicle. It has been observed that tillering at the lower nodes gives more and bigger panicles which helps to achieve the goal of 100 kernels per ear. Prepare the seedling bed with basal manure. Seed at 150 kg/ha for the female parent and 110-15- kg/ha for the male parent. At present the appropriate methods for raising seedlings are either to sow under plastic film the field or in a green house.
Sowing time

The proper sowing time is dictated by the number of days required from sowing time to panicle formation. The sowing should be so adjusted that the crop comes to panicle stage soon after the end of high temperature period.

Transplanting

Seed lings with healthy tillers are the basis for increased panicle size. For hybrid seed production, the seedlings of both parents should be standardized. Seedlings of the male parent for short duration varieties should be 20-30 days old with 5.5-7 leaves and 2-3 tillers and for long duration varieties 30-35 days old with 5.5-7 leaves and 2-3 tillers.

Planting ratio

The ratio of female and male lines is generally kept at 2:10-12; and the row spacing 10x10 cm for male parent and 20x15 cm for female parent. Two seedlings are planted per hill.

Row direction

both parents should receive good aeration and equal amounts of sunlight. Row direction should be nearly perpendicular to prevailing winds at flowering to ensure more cross-pollination.

Fertilization

Adequate fertilization is necessary. In general a seed field with moderate fertility should be treated with 200 kg N, 50kg P and 150kg K per ha; 90 per cent applied as a basal dose and 10 per cent after panicle differentiation.

Water management

Good water management is very important for regulating water, fertilizer, air and temperature of soil. Give shallow irrigation at the transplanting and tillering stages. In soils where water permeability is poor the field must not be allowed to remain under water for too long so that root growth could be encouraged. During the middle stages thewater should be drained off properly. Shallow water must be maintained again during the booting stage. During heading, if the air temperature is above 35 C, water should be applied during the day and drained-off at night so as too decrease soil temperature.

Other cultural practices are the same as described for conventional (open pollinated) varieties

Synchronization of flowering

Synchronizing the flowering of both parents is the key to increased yields. Technical measures such as staggering seeding dates of the male and female parents, sowing the male parents three times to extend the time pollen is available, and predicting and adjusting flowering dates may be adopted. Actual practices would have to be standardized foreach hybrid and the locations selected for the hybrid seed production.

  • Staggered sowing of male parents: Seeding date is usually determined by leaf age, effective accumulated temperature (EAT), and growth duration. In general, the period from initial to full heading of a CMS line is 4-6 days longer than for a restorer line. The first sowing of the male parent establishes the dates for second and third sowing. The second sowing is done when the leaf emergence on the first sowing is 1:1; the third sowing when the leaf emergence is 2.1. Thesecond sowing is the main parent. The planting ratio for sowing at different dates is 1:2:1.
  • By fertilizer application. Beginning about 30 days before heading, 3 or4 random samples of the main culm of both parents are tekn every 3 days. Young panicle development is compared under magnification. During the first three stages of panicle differentiation, treat the earlier developing parent with quick releasing N fertilizer; and spray the later developing parent with potassium di hydrogen phosphate. This adjusts development differences of 4-5 days.
  • By water management; During later stages of panicle differentiation, draining water from the field will delay male parent panicle development, higher standing water will speed panicle development.
Methods of Improving Seed Setting
  • Supplementary Pollination (Rope pulling). On calm days druign anthesis, supplementary pollination can be carried out. Panicles of the restorer lines are shaken by pulling along nylon rope (5 mm diameter) back and forth every 30minutes until no pollen remains on the restorer line. This method if often used on even topography and regularly shaped plots. In hilly, uneven topography with small, irregular plots, a bamboo pole may be used.
  • Leaf clipping; Leaves taller than the panicles are the main obstacles to cross pollination. Clipping leaves 1-2 days before initial heading increases the probability of pollination and outcrossing rate. The blade of flag leaf is cut back 1/2 to 1/3 from the top.
GA3 Spray

Spraying seed parent with 75 gm GA3/ha 60 ppm or more 2 or 3 times increases panicle exsertion and helps increased seed setting.

Roguing

The seed field should be free of rogues. Remove off-type plants in both the parents first before the onset of flowering stage and then soon after emergence of the panicle. Rogue out the plants of maintainer line, if any and the semi-sterile plants in the seed parent as often as necessary.

Harvesing of seed crop

Havest male rows first to avoid chances of mechanical admixture. Seed yield 5-15 Quintals/ha.

Wheat

Land Requirements

Land to be used for seed production ofwheat shall be free of volunteer plants. In addtion, the field should be well drained, free ofweeds, and the soil neither too acidic not too alkaline. Faily long intervals between crops of wheat is desirable in rotation, to reduce disease contamination of seed from diseases such as, kernal bunt.

Isolation Requirements

Wheat is normally a self-pollinated crop, but natural cross-pollination sometimes occurs. Theextent of cross-pollination varies from one to four per cent. It is usually suficient to isolate seed fields with a strip of 3 meters all around which is planted with a non-cereal crop, or left uncropped. In cases where variety is susceptible to diseases caused by Ustilago spp. (eg. loose smut) an isolation distance of 180 metres between seed field and other fields of wheat is recommended. The Indian minimum Seed Certification Standards require only 150 metres isolation from other wheat fields wherein loose smut infection is in excess of 0.1 per cent in the case of foundation seed production, and 0.5 per cent in the case of certified seed production.

Cultural Practices

Time of Sowing

Longduration varieties like C 306 should be sown during the first fortnight of November.

Short and medium duration varieties like Sonalika, HD 1982 should be sown during the second fortnight of November.

Preparation of Land

Bring the soil to a fine tilth by deep ploughing with a soil turning plough and by running a harrow before the presowing irrigation. Presowing irrigation is a must for uniform good germination. Give a light shallow ploughing or discing after presowing irrigation. Levelling is an important part of seed bed preparation. Keep the seed bed free ofweeds.

Broadcast BHC, 10 per cent dust at 25 kg per hectare just before the last harrowing or ploughing. It may be added to the fertiliser and applied. This will prevent white ant and Gujhia attack.

Source of Seed

Obtain nucleus/breeder's/foundation seed from a source approved by thecertification agency.

Seed Rate

The recommended seed rate for seed crop is 85-100 kg per ha. The seed should be treated with systemic fungicide to control loose smut.

Method of Sowing

The seed crop is sown in rows with seed drill, or behind the plough in furrows. The depth of seeding should be 5 cm. Seed drill should be thoroughly cleaned and checked before use. Sowing of one variety should be completed before taking up another variety, to avoid mixture. If, for any reason, it has to be used for another variety, it should be thoroughly cleaned and checked so that not even a single seed of the previous variety is left.

Fertilisation

The recommendced doses of fertilisers are 80 to 120 kg nitrogen, 50 to 60 kg phosphorus and 40 kg potash per hectare, in the light of soil test values and native fertility. If zinc deficiency is noticed in the soil, zinc sulphate at 15 to 20 kg per ha may be given at the seeding time.

Apply the whole of the phosphoric and potassic fertilisers and half of nitrogenous fertilisers while sowing, or just before sowing. Apply the remaining half ofnitorgenous fertiliser at first irrigation. Band placement of fertiliser gives better results. The fertiliser should not fall on the seed but should be dropped 5 cm away from the seed. Uniform fertiliser application is important. If soil has been tested, the recommendation of the soil testing laboratoryshould be followed.

Spacing

The row distance for seed crop should be kept at 22 to 22.5cm to facilitate roguing and inspection work.

Irrigation

Depending on the soil, four to six irrigations may suffice. The first irrigation should be given at crown root initiation stage, about 30 to 35 days after sowing. Other irrigations should be given at late tillering, late jointing, flowering, milk and dough stages. Two to three extra irrigations may be needed on light soils.

Interculture

Timely weeding and interculture are essential. Periodic hoeing and weeding keep the field free of weeds. For control of broad-leaved weeds spray 2-4 D at therate of 0.5kg active ingredient per hectare in 750 litres ofwater after 25 to 30 days of sowing. for control of Phalaris minor or wild oats make a pre-emergence application of pendamethalin (stomp) @ 1 kg ai per ha in 750 litres of water or spray Isproturon @ 1 kg ai per ha in 750 litres of water after 35 days ofsowing.

Insect and Disease Control

Adopt recommended IPM methods

Roguing

Two or three roguings may be necessary to bring the seed plot to seed certification standards.

The first roguing may be done just ahead of the flowering stage, or during flowering. It isessential that his roguing be done in time, to remove any off-type plants which are obvious at this state of growth. Failure todo so can allow natural crossing of rogues with normal plants, thus adding the variation in the following year. Obvious rogues at this stage include plants of different colour, plants susceptible tovarious diseases, tall plants in a dwarf variety, dense heads or other head variations, smutted plants and early heading plants.

A second roguing should be done just after flowering is completed, and before the crop starts to turn colour. If only a few rogues are present, this might suffice as the last roguing.

The third roguing should be done after the ear heads turn colour and start to mature. In addition to rougues previously mentioned, one is now able to rogue on thebasis of differences in colour of heads, colour of awns and variations in earhead type which are most easily discernable at this stage. In addition to off-types, the objectionable weed plants such Hiran Khuri (Convolvulus arvensis), Phalaris minor and weeds such as Chatri ;matri (Lathyrus species and Vicia species), as well as other crop plants, namely barley, oats, gram must be removed at this stage, or prior to harvest.

Harvesting and Threshing

Soon after maturity, the seed crop should be harvested to avoid shattering and losses due to uncertain weather. Delay of harvest in rainy and stormy weather may result in sprouting in the ear and thus rejection of the crop for seed.

Harvesting may be done by sickle, and later the threshing with stationary threshers orwith trampling done by bullocks. Care must be exercised to ensure that labourers do not mix the harvested certified seed with other wheat on the farm. Threshing should be done promptly. threshing equipment, if used, or the threshing floor must be thoroughly cleaned to prevent mixtures. The crop can also be combined directly in the field.

Drying, Cleaning and Bagging

Wheat seed is usually very dry at harvest time in North India, i.e., at nine to ten per cent moisture. To maintain the good quality in the seed, it is recommended that the seed be cleaned, treated and bagged immediately after threshing and prior to the start of the monsoon. the cleaned, bagged seed should be stored in a dry, insect and rodent proof warehouse.

Seed Yield

The average seed yield varies from 30 to 40 qtls per hectare.

Barley

Land Requirements

Land to be used forseed production of barley shall be free of volunteer plants. In addition, the land should be well drained and not acidic.

Isolation Requirements

The crop is generally self-fertilised. Usually not more than 0.15 per cent cross-pollination occurs. Pollination occurs while the head is in the boot in many varieties. An isolation of 3 meters all around the field is considered sufficient for maintaining varietal purity. However, to prevent spread of smut (Ustilago spp.). an isolation of 150 meters betwwen seed fields and such other fields where the infection of disease is in excess of 0.1 and 0.5 per cent for foundation and certified seed class respectively is necessary.

Cultural Practices

Time of Sowing

Mid-October to the 1st week of November.

Preparation of Land

Prepare the land well by ploughing, 3 to 4 harrowings followed by levelling.

Source of Seed

Obtain breeder's/foundation seeds from source approved by a seed certification agency. The seed should be treated with an organomercurial fungicide.

Seed Rate

75 kg per hectare.

Method of Sowing

The seed crop should always be sown in rows. Depth of seeding should be 5 to 7.5cm.

Fertilisation

Base the fertiliser application on the basis of soil test results. In the absence of soil test results apply 60 to 80 kg nitrogen, 30 kg phosphorus and 20 kg potash per hectare. Apply half of the nitrogen and the full amount of phosphorus and potash at the time of final preparation of the field for sowing. Apply the remaining half of nitrogen at the time of the first irrigation.

Spacing

Row to row 20 cm.

Irrigation

Irrigate seed fields two to three times namely at crown root stage, flower stage and milk stage.

Interculture

One weeding may be necessary to keep the seed field clean. Broad-leaved weeds can also be controlled by spraying 2-4D(1 kg per hectare, in 800 litres ofwater, 30 to 35 days after sowing.)

Insect and Disease Control

Adopt recommended IPM methods

Roguing, Harvesting and Threshing

Two or three roguings may be necessary to bring the seed plot to seed certification standards.

The first roguing may be done just ahead of the flowering stage, or during flowering. It isessential that his roguing be done in time, to remove any off-type plants which are obvious at this state of growth. Failure todo so can allow natural crossing of rogues with normal plants, thus adding the variation in the following year. Obvious rogues at this stage include plants of different colour, plants susceptible tovarious diseases, tall plants in a dwarf variety, dense heads or other head variations, smutted plants and early heading plants.

A second roguing should be done just after flowering is completed, and before the crop starts to turn colour. If only a few rogues are present, this might suffice as the last roguing.

The third roguing should be done after the ear heads turn colour and start to mature. In addition to rougues previously mentioned, one is now able to rogue on thebasis of differences in colour of heads, colour of awns and variations in earhead type which are most easily discernable at this stage. In addition to off-types, the objectionable weed plants such Hiran Khuri (Convolvulus arvensis), Phalaris minor and weeds such as Chatri ;matri (Lathyrus species and Vicia species), as well as other crop plants, namely barley, oats, gram must be removed at this stage, or prior to harvest.

There is no objectionable weed forbarley. the designated other inseparable crop plants for barley are wheat, oats and gram.

Seed Yield

30 - 35 qutl per hectare.