Cotton

Hybridization

Hybrid Cotton Seed Production

Hybrid of Cotton

  • Heterosis or hybrid vigour was reported by Mell in 1894. It exhibits high heterosis to the extent of 80 per cent or more in interspecific crosses and 30-50 per cent in intraspecific crosses.
  • Efforts were made to develop glabrous, pubescent plants with high gossypol content, which offer resistance to insect pests.
  • This is termed antibiosis, which is defined as biochemical and morphological traits – responsible for resistance to insect pests. Among the wild species, G.tomerntosum provide jassid resistance.
  • Of the four known sources of genetic male sterility. Gregg male sterile line of weaver, conditioned by MS 5 and MS6 double recessive gene is most promising.
  • Cytoplasmic male sterility of G.harknessi is most promising and G.longicalyx may provide an alternative.
  • Similarly G.anomalum and G.arboreum may provide degree of cytoplasmic male sterility. It is foreseen that cytoplasmic genetic male sterility 9GCMS) based hybrid system will reduce the cost of seed production by 50 per cent.
  • Therefore CGMS may replace the conventional hybrids in the near future. Some of the important commercial hybrids released in India are already presented. These hybrids have an yield potential of 3 to 4 t ha-1 of seed cotton under irrigation with high responsiveness to added fertilizer. The interspecific tetroploid hybrids are now successfully cultivated in well distributed rainfall zones with an yield potential 2 to 2.5 t ha-1 of seed cotton. The ginning out-turn is 33 to 34 per cent.
  • Most recently released hybrid in 1996 is DHB 105. It is an interspecific hybrid involving CPD 428 (G.hirsutum) as female parent and B 82-1-1 (G.barbadense) as male. This hybrid is suited to entire southern region of Indian with an yield level of 2.5 to 3.0 t ha-1 seed cotton or lint yield of 0.8 to 1.0 t ha-1. The ginning out turn is 34 per cent, the mean fibre length is 32 to 33 mm.
  • It has better fibre properties than DCH 32 and HB224. It tolerates red leaf blight as it has more chlorophyll content. It is tolerant to boll worm as it has more tannin and low reducing sugars and protein.
  • Another important intra-hirsutum hybrid released in 1995 is DHH 11. It yields 2.0 to 2.5 t ha-1 of seed cotton and gives about 40-50 counts.

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Hybrid seed production

  • The conventional method of hand pollination and emasculation is still followed in India which is costly and labour intensive. "Doak method’ (thumb nail) of crossing is practiced in hybrid seed production. The emasculation and bagging of female parent bud is better done in the evening hours (3.00 to 6.00 pm), while they are pollinated on the subsequent day in morning hours 8 to 11 am or even upto 12.30 pm. The emasculated flower is bagged with red tissue paper or red straw tube. But after pollination, the red bag or tube is replaced with white bag/tube. The pollen of the male flower are collected and kept under protection in covered trays. A thread is tied at the base of the pedicel for easy identification of pollinated flowers. All missed flowers and unused male flowers must be removed.
  • Male and female plants are sown in shallow furrows (30 cm deep). Female parents are spaced 2 m apart while male parent at 1 m escapement. Delineated seeds (2 or 3) are sown per hill. For seed production, it should be well manured, fertilized and free from pests and diseases. Seed production plots receive nearly 10 to 15 t FYM/ha with a fertilizer dosage of 250 : 125 : 125 N : P : K kg ha-1. Gaps are filled using seedlings grown in polythene bags/tubes. About 60 to 75 labourers per day are needed for hand emasculation, crossing and bagging per ha, at peak flowering period. We should ensure 100 female parent stand, that is free from diseases and pests. At the rate of 2.5 kg ha-1 seed rate, India needs over 6,000 t of hybrid seed per year and this requirement is ever increasing. Obviously, there is good cause to be involved in hybrid cotton seed production.

Advantages

  • Superior yield performance coupled with superior fibre properties.
  • Wider adaptability
  • Good price for the produce
  • Employment generation through labour intensive hybrid seed production.
  • Short duration hybrids can fit into multiple cropping system.

Disadvantages

  • High cost of seed and cultivation.
  • Difficulty in seed production.
  • Neps and motes especially in interspecific hybrids.

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Karnataka

Cotton

Cotton Management