Cotton seed production in hybrids & varieties

For production of seeds for cultivation or developing new varieties or hybrids, certain standards should be followed to get good quality and pure seeds.

1. PRINCIPLES OF SEED TECHNOLOGY 3(1+2) SEED PRODUCTION IN COTTON VARIETIES AND HYBRIDS BY TO BASKAR S Dr.DHIVYAPRIYA D BATCH-A Asst. Prof. CB.AG.U4AGR19018 19GPBB212

2. COTTON (QUEEN OF FIBRES) BOTANICAL DESCRIPTION Scientific name : Gossypium sp. Family : Malvaceae Leaves : Three lobed leaves Branches : Sympodial & monopodial

3. Floral biology : Bisexual flowers on sympodial branches Simple, solitary, terminal, hermaphrodite 5 sepals, united and cup shaped 5 petals Yellow to cream in colour with purple spots After pollination, light pink to purple in colour (within a day) Monodelphous , often cross pollinated (>60%)

4. Anthesis : Anthesis time will be vary on different species. Climatic factors (temperature) also affect it. Asiatic cotton – 8 to 10 am American cotton – opens earlier Receptivity of stigma – 8 to 10 am MAJOR 4 CULTIVATING COTTON SPECIES Gossypium arboreum (K 10) (2n=26) Gossypium herbaceum ( Uppam ) (2n=26) Gossypium hirsutum (MCU varieties) (2n=52) Gossypium barbadense ( Suvin & Suguna ) (2n=52)

5. METHOD OF SEED PRODUCTION Seed production techniques will be different for both varieties and hybrids. 1. VARIETIES Open pollination is done under isolation and varieties are multiplied. For nucleus seed production, selfing of flowers is done with cotton lint (dipped in clay or red earth). 2. HYBRIDS It is of two types. They are interspecific and intraspecific hybrids. Interspecific hybrids Crossing among same genus of different species Hybrids G. hirsutum x G. barbadense (Parentage) i ) Varalakshmi : Lakshmi x SB298 ii) Jayalakshmi / DCH 32 : DS 28 x SB 425 iii) TCHB 213 : TCH 1218 x TCB 209

6. Intraspecific hybrids Crossing among the same species of different subspecies Savitha : T 7 x M 12 METHODS OF HYBRID SEED PRODUCTION 1. Conventional method Emasculation and dusting is the conventional method for hybrid seed production. Select the female line flowers at 1 day before opening (3-6 pm) Remove the staminal column by needle Cover the female parent for identification Select the male parent at the time of anthesis Pluck the male parent & dust the female parent Cover the female parent to prevent the contomination by foreign pollen One male parent is enough to dust 4-5 female parents & receptivity of stigma is 46 hrs.

7. STEPS IN HYBRIDIZING TECHNIQUE Emasculate and dust the flowers (buds) appearing during first six weeks of reproduction phase. Emasculation time – 3 to 6 pm & pollination time – 9 to 12 am Emasculated and pollinated female parents are covered with paper bags and choose optimum aged and sized parents. Stop the crossing programme after 9 th week and remove the further appearing buds. Nip the top and side shoots to stop further vertical and horizontal growth. Optimum irrigation should be given Pick the ripened and opened bolls and sort it out to check that they are crossed bolls and stored in gunny bags. Rain touch or hard lock cottons are separated to avoid the poor germination. Store the seeds in cool dry place till it is given to processing unit.

8. 2. Non conventional method Genetic male sterility (GMS) is the non conventional method for producing hybrids. In this, female parent is segregated into 50:50 ratio of male sterile and male fertile plants. Then, male fertile are removed and male sterile plants are crossed with requiring male line. e.g. Suguna : Gregg x K 3400

9. FIELD REQUIREMENTS OF COTTON FOR BETTER GROWTH 1. Land Fertile black cotton soil with ridges & furrows which should be free volunteer plants, pest and pathogen (wilt disease) 2. Season Winter crop : August – September Summer crop : February – March 3. Seeds & sowing Tagged seeds should be obtained from authenticated sources ( agri clinic) & seeds are dibbled at optimum depth (4-8 cm). 4. Seed treatment Delinting ( 100ml of concentrated sulphuric acid in 10 litre of water for 1 kg of seeds at 2-3 min and washed by water) to remove cotton fuzz around the seeds. Seed hardening 1% prosopis & pungam leaf extract to resist water stress problems.

10. Azospirillum is mixed with cotton seeds at 600 g/ha. Then 2kg of azospirillum /ha is mixed with 25kg of FYM and 25kg of soil and applied on the seed line. 5. SEED RATE (kg/ha) Varieties : 15 kg (fuzzy seeds), 7.5kg ( delinted seeds) Hybrids : 3.5 kg ( Jayalakshmi ), 1 kg (TCHB 213) Male : 2kg Female : 4kg 6. Spacing For hybrids, planting ratio is 8:2 of female and male parents. Duration Varieties Hybrids Long duration 90 x 30 cm 120 x 60 cm (female) Short duration 60 x 30 cm 90 x 60 cm (male)

11. 7. Isolation distance (m) 8. Manure & fertilizers Compost – 12.5 tons/ha Total NPK – 100:50:25 kg/ha Basal NPK - 50:50:25 kg/ha Top dressing – 25 kg/ha @ 40-45 days after sowing 25 kg/ha @ 70-75 days after sowing 9. Foliar spray 2% of DAP on 60 th ,70 th ,80 th & 90 th day after sowing 10. Micronutrient application Mix 12.5 kg of TNAU micronutrient mixture with 37.5 kg of sand (to make it as 50kg) for 1 ha. Type Foundation seed Certified seed Varieties 50m 30m Hybrids 50m 30m

12. 11. NAA application 40 ppm of NAA (40 mg of NAA in 1 litre of water) at 40/45 th day. Repeat it after 15 days of first spray. 12. Irrigation management Once in 10 days. Regular irrigation in critical stages (from boll initiation to boll maturation stages.

13. 13. Intercultural operations Topping Nip the top and side shoots (10 – 12 th) to stop excessive vegetative vertical and horizontal growth. Roughing To maintain purity, roughing is done for off types, selfed plants from vegetative to harvest phase. It depends on the plant characteristics such as leaf and boll size, flower colour, number of sympodia , hairiness etc…

14. 14. Specific problems Boll shedding will occur in hotter climate or in lesser irrigation. For controlling, 40ppm of NAA & 20ppm of cycocel ( ccc ) is sprayed. 15. Field standards For foundation seeds, maximum permitted off type is 0.1% (both varieties & hybrids). For certified seeds, maximum permitted off type is 0.2% (varieties) & 0.5% (hybrids).

15. 16. Harvesting stage Initiation of hair line cracks on dried bolls Hand picking is done at 45 days after anthesis (10 – 11 am) Moisture content – 30 to 35 % Normally, 7 pickings are done but for seed production early 4-5 pickings are done. Kapas are taken from well burst bolls only.

16. PROCESSING Kapas sorting – Hard locks (without proper bursting) & pest attacked (boll worms) are sorted manually for good germination. Ginning – It is done to remove dust, dirt and fuzz from seeds in processing unit. Acid delinting – Using sulphuric acid chemically lint is removed from the seed.

17. Grading – Seeds are graded by specific gravity method by flotation technique using water in which sinkers (brownish) are good seeds. In this, floating, reddish (immature) & insect damaged (holed) seeds are removed. Then, seeds are dried. Certification – Seeds are certified by seed inspector or certification officer based on its physical and genetic purity and it is sealed in bags. It is used for commercial sale and uncertified seeds are used by that company for further multiplication .

18. SEED STANDARDS Characters Foundation seed Certified seed Physical purity(%) 98 98 Genetic purity (%) 100 100 Germination (%) Variety 65 65 Germination (%) Hybrids 75 75 Weed & other crop seeds 1/5kg 1/5kg

19. SEED STORAGE Graded good quality seeds are stored in moisture pervious container (upto 8-9 months) or in moisture proof container (upto 12-15months). It is treated with thiram @ 2.5g/kg of seeds which preserves storability. In mid storage, seeds are shaded and sun dried to maintain 10-12 % of moisture content.

20. REFERENCES www.cicr.org.in www.agritech.tnau.in www.seednet.gov.in http://eagri.org

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