Development and evaluation of India's first intraspecific Gossypium barbadense cotton recombinant inbred mapping population for extra-long staple fibre traits.

Fibre quality improvement in Gossypium hirsutum is one of the long thought objectives for sustainability of cotton improvement. The efforts to transfer G. barbadense alleles in to G. hirsutum for enhanced fibre quality is still under process across the world. To meet the future fibre quality demand in India, here we report development of G. barbadense X G. barbadense recombinant inbred mapping population that has huge potential for precise mapping of extra-long staple traits. The two-location evaluation and variability analysis for extra-long staple traits such as fibre length (24.91 to 34.06 mm), fibre strength (25.02 to 35.86 g/tex), micronaire (2.89-4.57), uniformity index (64.08-98.83), fibre elongation (5.37-6.60) and maturity ratio (0.48-0.76) were highly satisfactory. The principal component analysis indicates that the principal component-1 explaining 23.12% variance had maximum values of Eigen vectors explained by fibre strength (-0.464), length (-0.469), elongation (-0.448), maturity ratio (0.312) and micronaire value (0.306) indicating the worth of the population for which it was developed. The correlation analysis indicated that the fibre length and strength could be simultaneously improved without any impact on seed cotton yield since both traits were positively associated with each other and also showed nonsignificant association with seed cotton yield. A total of 255 recombinant inbred lines (RILs) showed normal distribution from both Z-score of skewness/kurtosis analysis and quartile-quartile plots indicating that they can be readily utilized for genotyping with latest available technologies such as genotype-by-sequencing for effective mapping of extra-long staple traits in cotton.

Biochemical and molecular dissection of thermo-sensitive genetic male sterility in diploid cotton (Gossypium arboreum L).

Diploid cotton, due to its inherent problem of stamen brittleness, its found unsuitable for traditional method of hybrid seed production which involves hand emasculation followed by pollination. Due to shortfall in other methods viz., Genetic Male Sterility (GMS), as well as, Cytoplasmic Genetic Male Sterility (CGMS), hybrid seed production in diploid cotton becomes costly and thereby, covers less area among the total cotton grown area. Thermo-sensitive genetic male sterility, which overcomes the drawbacks of both GMS and CGMS can be an effective tool in coming years for hybrid cotton research. Understanding fertility and sterility variations, their relation with biochemical changes in plant is important before its application in plant breeding. Hence, the available TGMS line, Ga TGMS-3 obtained at Cotton Research Centre, UAS, Dharwad was studied for callase activity and markers associated with TGMS. The line Ga TGMS-3 had fertile anthers and showed less callase enzyme activity at pre-meiosis stage, high enzyme activity at tetrad releasing microspore stage and no callase activity during other stages. The counterpart TGMS sterile anthers displayed little higher callase activity at pre-meiosis stage, high activity at tetrad stage, but poor activity at tetrad releasing microspore stage. During tetrad stage, TGMS sterile anthers showed high callase enzyme activity giving every chance for early release of poorly developed microspores as compared to fertile anthers. At tetrad releasing microspores stage during which fertile anthers had strong callase enzyme activity led to microspores being released normally and developed normal pollen grains as compared to sterile anthers. The present investigation revealed that NAU2176, NAU2096 and BNL1227 primers can be used as tightly linked markers for TGMS trait, as evident from their differential expression in fertile and sterile anthers.