Pearlmillet heterosis and hybrid seed production


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Pearlmillet heterosis and hybrid seed production

  1. 1. PEARL MILLET Heterosis and Hybrid Seed Production
  2. 2. Pearl millet (bajra)• Family:- Gramineae• Genus:- Pennisetum• Species:- americanum (l)k.Schum Glaucom (l) r.Br• Chromosome no.:- 2n=2x=14• Related species:- P.purpureum• Origin:- Africa
  3. 3. PLANT DESCRIPTION•Pearl millet [pennisetum glaucum (l.) r.Br.] is awarm season crop, planted in early summer whensoils have warmed up.• The crop is primarily cross pollinated, andfollowing pollination, it takes a flower about 30more days to develop into a mature seed.•It has fast root development, sending extensiveroots both laterally and downward into the soilprofile to take advantage of available moisture andnutrients.• Uses:- hay, pasture, silage, seed crops, and food.
  4. 4. Mode of Pollination•Pearl millet is predominately protogynous.(The stigma is emerged before the antherappears which facilitates cross pollination).•Development of hybrids without Emasculation.•Self pollination may occurs on late tillers.•Wind is major cross pollination agent.•Insects also effect cross pollination.
  5. 5. Controlled Pollination• For controlled selfing• Bag the spikes prior to emergence of style when most part of head is in boot.• For selfing, water repellent brown paper bags, or kraft paper bags sealed with waterproof adhesive, are used.• Insecticidal dust, such as DDT putted in bag to give insect control.
  6. 6. • Controlled cross pollinations• Female heads are enclosed, before emergence of styles in waterproof glassin paper bags.• When most of stigmas are exerted, pollen collected from required male is dusted on female head after removing bag.• Bag the spike after gross pollination has taken place.
  7. 7. Reasons for Exploitation of Heterosis •Very high heterosis (5-250) •Highly cross pollinated crop •No emasculation is required •High seed to seed ratio •Low cost of seed production •Availability of CMS lines
  8. 8. various trait used for exploitation of heterosis in pearl millet-• Days to maturity• Plant height• Fodder yield quality• Grain color quality• Panicle size• Hybrid vigor• Grain yield• Threshability• Resistance to diseases and insects are considered.
  9. 9. Seed Production• Before the exploitation of CGMS in 1965, pearl millet varieties were used to be oppen pollinated.• After 1965 the development of first ever hybrid HB1 by using CMS resulted in the hybrids with great yeild potential and disease resistance.
  10. 10. SEED CLASSES Nucleus seed Breeders seed Certified Seed Foundation SeedTruthfully Labelled
  11. 11. Seed production procedures of various classes are desribed here:-Pearl millet varieties vary slightly with each stage of multiplication, needed to maintain genetic purity at th early stages, and also, there should always be onward flow from one stage to the next.
  12. 12. Figure : Flow diagram of a three-stage seed production scheme for pearl millet varieties.
  13. 13. NUCLEUS SEED PRODUCTION•Nucleus seed refers to the seed producedby the breeder who developed the particularvariety and the parental lines of hybrids.•Original seed.•100% genetic and physical purity.•nucleus seed is multiplied and maintained byselecting individual pods/spikes and growingthem.•available only in small quantity. •NO TAG in nucleus seed.
  14. 14. Foundation seed• Only breeder seed is used to plant these plots at least 400 m away from the nearest pearl millet, napier grass, and wild pearl millet fields.• As a precautionary measure, first plant a belt of 5-10 m wide around the perimeter of the plot with the same seed, at least 7-10 days before planting in the center. The perimeter can be planted dry while the center can be planted, just after the rains.• TAG COLOR is white.
  15. 15. BREEDERS SEED• Breeder seed is the progeny of nucleus seed.• Production is controlled by the originating plant breeder who developed the variety.• Breeder seed is genetically so pure.• TAG COLOR is golden brown.
  16. 16. Seed Production technology •Planting density •Planting ratio •Distance from pollen source •Planting direction •Planting time •Presence of off types
  17. 17. Hybrid seed productionA hybrid variety is first generation (F1) from crosses between two • purelines • inbreds • open pollinated varieties • clones or other population that are genetically dissimilar.Requirements:- • Presence of hybrid vigour. • Elimination of fertile pollen in female parent. • Adequate pollination by male parent.
  18. 18. Types of Hybrids• Single cross hybrids (A x B)• Double cross hybrids (A x B) x (C x D)• Three way hybrids {(A x B) X c}• Top cross hybrids {c X OPV}• Hybrid blends• Inter population hybrids• Chance hybrids
  19. 19. Hybrid Seed Production Using CGMS• Pearl millet crops use CYTOPLASMIC-GENETIC MALE STERILITY system in hybrid seed production that is caused by an interaction of the sterility-inducing factors in the cytoplasm with the genetic factors in the nucleus.• The system is based upon:- 1. A cytoplasm that produce male-sterility. 2. A gene that restores fertility.steps involved :- 1. multiplication of CMS(A) lines. 2. multiplication of maintainer (B) and restorer lines. 3. production of hybrid seed (AxR)
  20. 20. PARENTAL LINESA-lines:- it is the male sterile parent line.B-lines:- the fertile counterpart of A-line, doesnt have fertility restoring genes and used to maintain A-line.R-line:-The male fertile line carries genes for fertility restoration.
  21. 21. Maintainance of A & B-Lines•Grow A-line and its corresponding maintainer, B-line together in an isolated plot.• The isolation distance for A x B production fieldsis at least 1 km.• A ratio of 1A: 1B rows is maintained.• Pollen produced by the B-line fertilizes the male-sterile plants (A) and the seed produced thus, givesrise to the A-line again.
  22. 22. Maintenance of R-line•The pearl millet R-line could be either an inbred line oropen-pollinated variety which can be multiplied as variety.The seed of R-line are produced by multiplying the seed inisolated plot having distance 1000 m.•Any plant in the r-line plot appearing different from the trueR-type should be uprooted, or rogued before anthesis.•Purity of the parental seed is very important because itaffects the quality of hybrid seed that is generated.
  23. 23. Pollen (cross) AXB Pollen (self) Pollen (cross) AXR Pollen (self) F1scheme for Hybrid Seed Production In pearl millet usingCGMS lines
  24. 24. Maintenance field Hybrid seed production field isolation1:1 A & B rows 4:1/6:2 A &B rows Harvest of R-line gives R-seed Harvest of A-line gives A-seed Harvest of A-line give Hybrid seed (F1) Harvest of B-line gives B-seed Layout of hybrid seed production plot
  25. 25. CAUTIONS• The pollen shedders in the A-line rows must be identified and uprooted each morning during the flowering period.• Normally, no more than 0.05% genetic off-type are permitted at final inspection in foundation seed.• Since both A-lines and B-lines exhibit synchronous flowering, seed yields on the A-line in A/B seed production plots are relatively better than in the A and R (hybrid) production plots.• Seed of the B-line harvested from the A/B production plots might be reused for the next generation, depending on the seed laws of the country.
  26. 26. CERTIFIED SEED• Certified seed is the seed, which is certified by a Seed Certification Agency notified under section 8 of indian seeds act(1966).• Certified seed consist of two class- 1.Certified foundation seed-progeny of breeder seed. 2.Certified seed-progeny of foundation seed. TAG COLOR is blue.
  27. 27. R-LINE A-LINEPattern of R-line And A-Line For Certified Hybrid Seed Production
  28. 28. Identification of Potential Hybrid Parents (A-, B-, and R-lines)• Potential male and female parents for hybrid seed production are identified by crossing male-fertile plants (inbreeds, varieties, germplasm, breeding stocks in advanced generations, etc.) to a male-sterile line (A-line) and observing their corresponding hybrids in small plots of an observation nursery. male fertile X male sterile F1• A few plants of each cross are subjected to a BAGGING TEST, i.e., covering a few panicles with paper bags before anthesis, and observing seed-set under the bag after a few weeks.
  29. 29. • A normal bisexual fertile panicle would exhibit nearly 100% seed set whereas in crosses with A-lines, the following three types of hybrids are encountered:-1. Hybrids have no seed-set, i.e., male-sterility is maintained in these hybrids. The corresponding pollen parent is classified as a non -restorer/maintainer or B-line and as a potential new A-line.2. Hybrids exhibiting complete seed-set under the bag, i.e., male fertility has been completely restored in these hybrids. The corresponding pollen parent is classified as a potential male-parent /restorer line or R-line and could be useful in producing hybrids.3. Hybrids exhibiting partial seed set under the bag. Such hybrids and their male parents are rejected for further studies because experience shows that it is difficult to extract stable R-lines or B-lines from such parents.
  30. 30. HYBRIDS
  31. 31. HHB 50 •Highly productive under good management •High dry fodder yield •Highly resistant to downy mildew
  32. 32. HHB 60 •Tolerant to drought •Medium maturity (70 days) •Resistant to downy mildew
  33. 33. HHB 67 •Extra early maturity •Most adaptive hybrid in drought hit areas •Suitable for inter cropping
  34. 34. HHB 68 •Early maturity •Multiple disease resistant •Suitable for drought hit areas
  35. 35. HHB 146 •Combines high grain with high biomass •Tall height, long head •Tolerant to lodging and salinity •Highly responsive to nitrogenous fertilizers
  36. 36. HHB 67 Improved •Extra early maturity •Highly resistant to downy mildew •Improved version of HHB 67 through MAS
  37. 37. HHB 197 •High Yield Potential •Long Bristles •Resistant to Downy Mildew & Smut
  38. 38. HHB 223 •High yield potential (55 q/ha) •Conical, medium long ear head •Purple long bristles •Highly resistant to downy mildew