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Seed classes, seed Production and purity tests in Sorghum By IDK Atokple

Seed classes, seed Production and purity tests in Sorghum By IDK Atokple. Why genuine seed. Plant breeder’s job not ends with development of variety/hybrid Genuine and pure seed available to farmers/producers Genetic purity reflects performance and adoption Higher income to farmers

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Seed classes, seed Production and purity tests in Sorghum By IDK Atokple

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  1. Seed classes, seed Production and purity tests in Sorghum By IDK Atokple

  2. Why genuine seed • Plant breeder’s job not ends with development of variety/hybrid • Genuine and pure seed available to farmers/producers • Genetic purity reflects performance and adoption • Higher income to farmers • Helps to distinguish it from other genotypes • Useful in IPR/PBR • Enhances reputation of breeder/organization

  3. Testing/releasing procedures • Breeders multilocation testing • AICSIP testing and identification • Sufficient nucleus/breeders seed • Description of the varieties/parents/hybrids • Recommendation to State/Central Varietal Release Committee

  4. Nucleus seed • Breeder seed • Foundation seed • Certified seed Classes of seed

  5. Producing agency Category Nucleus seed (Basic seed) Agricultural universities and Research institutes Breeder seed (Stage-I) Breeder seed (Stage-II) -do- Agricultural universities and seed corporations (public/private) Foundation seed (Stage-I) Foundation seed (Stage-II) Seed corporations (public/private) Certified seed (First generation) Commercial seed Farmer Seed-multiplication chain

  6. Anthers from male-fertile (left) and male-sterile (right) panicles A comparison of developing inflorescences of a male-sterile A-line (left side of each pair) and restorer R-line (right side of each pair) in different growth stages Insertion of a paper bag onto a pollen-shedding panicle

  7. Nucleus seed production Initial handful of seed originating through selection/breeding by the breeder Produced by originating breeder Steps Variety/R-line • Self each plant after rouging off types • Plant head to row next generation and rogue out off types • Self an bulk progenies conferring to the original description

  8. Nucleus seed production A/B-lines • Plant A/B in 2 rows of 1 m • Rogue out off types/pollen shedders • Bag before anthesis and make plant to plant crossing between A and B • Plant the seed of paired A and B, rogue out off types/pollen shedders in A • Make plant to plant crosses in two/three pairs which confirm to the original description • Finally bulk within A-line and B-line progeny which confirm to the original line

  9. Breeder seed production Variety/B-line/R-line • Varieties, B- and R-lines are pure lines • Sown in isolated plot • Maintain >300m isolation from other sorghum cultivars for B- and R-lines • >200m from other sorghum cultivars for varieties • >400m from Johnsons grass/other forage/ grassy sorghum types for all types • Crop grown under assured irrigation facilities • Recommended package of practices followed • Rogue out off types before anthesis • Harvest, clean and dry the seeds to <12% moisture

  10. Breeder seed production (contd..) Male-sterile line • Plant A- and B-line in 4A:2B or 6A:2B ratio • Plant B-line all along the borders • Maintain > 300m isolation from other sorghum cultivars • >400m from Johnsons grass/other forage/ grassy sorghum types for all types • Rogue out off types in A- and B- and pollen shedders in A-line before anthesis • Crop grown under assured irrigation • Recommended package of practices followed • Harvest B-line first followed by A-line • Seed collected on A-line gives rise to A-line • Label the seeds correctly • Harvested B-line seed can be reused for next generation • Clean and dry the seeds to <12% moisture

  11. Foundation seed production • Intermediate stage between breeder and certified seed production • Requires certification • Produced by State Seed Corporations (SSCs)/Central Seed Farms (CSFs)/Extension Agencies (EAs) • Production supervised by concerned breeders/representatives of SSCs/CSFs/EAs and seed certification agencies

  12. Certified seed • Last stage of seed production chain • Directly goes to farmers/producers • Produced on large scale by public/private sectors/EAs/experienced growers • Quantity produced depends on the demand for hybrid seed • Requires certification • Production supervised by concerned breeders/ representatives of SSCs/CSFs/EAs and seed certification agencies

  13. Certified seed (contd..) Varieties • Steps are similar to breeder seed production • Maintain >100 m isolation from other sorghum cultivars • >400 m from Johnson grass/other forage/ grassy sorghum types Hybrids • Production involves A- xR- (hybrid) seed production • Plant designated A- and R-lines in 4A:2R or 6A:2R ratios in isolated plots • R-lines are planted all along the borders • Maintain >300m isolation from other sorghum cultivars • >400m from Johnson grass/other forage/grassy sorghum types • Crop grown under assured irrigation • Recommended package of practices followed

  14. Certified seed (contd..) • Synchrony in flowering is most important • Staggered planted depending on the difference in days to flowering between A- and R-lines • Flowering behavior of A- and R-lines interact with day length and temperature • Staggered planting is standardized for each seed production area • Careful manipulation of nitrogenous fertilizers and irrigation improves synchrony of flowering • Rogue out off types, pollen shedders and diseased heads in A-lines before anthesis and off types and diseased heads in R-lines • Supplementary pollination techniques such as beating R-lines with sticks or brisk walking between R-line rows enhances seed yield of A-lines • Seed harvested in A-line is hybrid seed that goes to farmers/producers • Seed collected on R-line is not permitted to be re-used for A x R seed production • Harvested seed on A-line is cleaned and dried to bring the moisture to <12%

  15. Minimum isolation distance required

  16. An isolated breeders seed production plot of A- and B-lines at ICRISAT An isolated breeders seed production plot of S 35 variety at ICRISAT An isolated JKSH 22 hybrid seed production plot at Nandyal, AP

  17. Maximum permitted level of pollen shedders, off-types, and diseased heads for foundation and certified seed of sorghum

  18. Planning seed production

  19. Causes of contamination • Natural crossing with another cultivar • Mutation • Unclean harvesting environment • Carelessness at processing plant • Mistakes in bagging and tagging

  20. Purity test of hybrids, parental lines and pure-line varieties of sorghum • Genetic purity • Methods of genetic purity assessment • Physical examination of seed in the laboratory • Chemical treatment of seedlings: Phenol reaction test – soaking in 0.2% Na2CO3 and then in 1% phenol and incubating at 30oC for 24 h. • Shoot, root and seedling growth response to added chemicals (DDT, BHC, Folidol, Thiram, Captan, GA3, PEG etc). • Electrophoresis – separation of proteins • Field plot test: minimum of 400 plants are required/grow-out test

  21. Purity test of hybrids, parental lines and pure-line varieties of sorghum (contd..) Genetic purity requirements for different classes of sorghum Seed classGenetic purity (%) Foundation seed 99.0 Certified seed 99.0 Varieties 98.0 Hybrids 95.0

  22. Purity test of hybrids, parental lines and pure-line varieties of sorghum (contd..) • Seed standards Seed standards for foundation and certified seed of sorghum.

  23. Eligibility requirement for certification • Seed of varieties and hybrids meant for certification should be from a source that is reliable and approved by the certification agency • Land requirements • The seed production field offered for certification should be irrigated at least three weeks before sowing, and plowed sufficiently ahead of sowing to destroy volunteer seed of sorghum • Care should be taken to remove Sorghum halepense seed in the field and within the isolation distance

  24. Phases of seed certification • Application for certification • Establishing a seed source • Field inspections to verify conformity to field standards • Post-harvest supervision • Grant of certificate and tagging

  25. Field inspections Four field inspections made during the crop period: First inspection: During preflowering stage Second and third inspections: During flowering stage Fourth inspection: During preharvest stage

  26. Certification standards • The production and handling of foundation seed and certified seed must be supervised and approved by the certification agency • The seed must meet the standards prescribed by the certification agency

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