Project for Development of Commercial Hybrid Cotton

Abstract

The improvement made in quantity and quality of our cotton through conventional breeding is not enough to raise our yield to the level of developed countries. Consequently, to achieve a break through we restored to exploitation of hybrid vigor for production of F1 hybrid cotton. The magnitude of hybrid vigor is greater with the diversity of the parents involved in the cross. Hence choice was made for interspecific hybrid involving Hirsutum and G. barbadense parents. The production of commercial hybrid cotton necessitates three breeding programmes, (1) to develop environmentally stable male sterile female parent usually as pairs of isogenic “A” (male sterile line) and “B” (pollinators lines (2)) to develop effective fertility restorer male parent (R line) and (3) an extensive testing of hybrid combinations to isolates the best performing one with respect to desired character. To isolate the best performing hybrid combination, 66 F1’s was evaluated against Qalandri, the standard variety. In all, 34 hybrids were found superior to Qalandri our yielding it by 0.5 to 111.9%. But for gaining popularity with growers as well as incentive for its cultivation, the hybrid should give at least 40% more yield than qalandri so as to compensate the labor and cost of its cultivation. Such superior hybrids were nine which have CM-10, Deltapine-70 or NIAB-78 as hirsutum parent in combination with barbadense cultivar. The later two are known heat tolerant. A further comparison of these hybrids between themselves will lead to isolate most suitable combination for production of commercial hybrid cotton through cytoplasmic male sterile system. The cost of F1 hybrid seed production is compared very high to that of F2 hybrid. Therefore, F2 hybrid were evaluated against standard variety Qalandri to study the feasibility of producing F2 hybrid commercially instead of F1 hybrid. But the results were not encouraging due to genetic breakdown and consequently appearance of unbalanced, sterile ad variable population giving poor yield and poor uniformity ratio of lint. Therefore, it has been concluded that F2 commercial hybrid cotton cannot be a commercial success on hirsutum barbadense combination. Another attempt towards development of commercial hybrid cotton, besides cytoplasmic male sterile system, can be made through genetic male sterile system. In genetic male sterile line (ms5-ms6) a normal pollen restores fertility in F1. Therefore, different G. barbadense cultivators were crossed onto the genetic male sterile line. But none of their hybrid could give better yield than the standard Qalandri. However, all hybrids gave more seeds and lint indices and produced longer staple than Qalandri. The trial needs to be repeated with greater number of hybrids for conclusive results. To have a readily available knowledge of suitable parents for making cross combinations, general combining ability studies were carried out that revealed that NIAB-78, CIM-10, Deltapin-70, and Dixieking were the best combiners with respect to yields. Of these, CIM-10 and Deltapine-70 were good combiners for ginning out turn whereas NIAB-78 and Dixieking for staple length. In barbadense group, Tadla-12, Karnak and Pima-S2 were good combiners yields. Karnak was also good for ginning out turn and Tadla-12 and Pima-S2 for staple length. The evaluation studies on restoration for fertility revealed that early maturing Pima restorer was the best. The general combining ability studies carried out on CMS x R crosses indicated that cytoplasmic male sterile Coker-304 and super Okra Ne super hairy were the best whereas in fertility restorer’s early maturation Pima gave highest general combining ability in fruit setting. The work on conversion of local cultivars to cytoplasmic male sterile has been taken up and needs to be continued further. The research carried out over a period of three years has yielded substantial results. The best combinations of parents to manifest high degree of heterosis in F1 generation have been isolated and best fertility restorer for inducing fertility in cytoplasmic male sterile has been identified. These are basic requirements which have now been achieved for producing of commercial hybrid cotton.