SAMBA MURTHY, J.S.V.VINEELA, N2016-06-072016-06-072011http://krishikosh.egranth.ac.in/handle/1/66887The present investigation was carried out at Agricultural College Students’ Farm, Bapatla, Andhra Pradesh during kharif 2010-11 with 84 intra- hirsutum cotton (Gossypium hirsutum L.) hybrids derived from 19 parents (12 lines and 7 testers) which were developed from new heterotic gene pools through line x tester fashion along with two checks. Information on genetic variability, heritability, genetic advance as per cent of mean, correlation and the magnitude of direct and indirect effects, combining ability and standard heterosis was generated. The data was recorded on twenty one characters viz., plant height (cm), days to 50% flowering, number of monopodia per plant, number of sympodia per plant, relative water content (%), specific leaf weight (mg/cm2), crop growth rate at peak flowering stage (g/m2/day), crop growth rate at boll formation stage (g/m2/day), crop growth rate at maturity stage (g/m2/day), number of bolls per plant, boll weight (g), ginning out-turn (%), seed index (g), lint index (g), 2.5% span length (mm), micronaire value (10-6 g/inch), bundle strength (g/tex), uniformity ratio, fibre elongation (%), lint yield per plant (g) and seed cotton yield per plant (g). The analysis of variance revealed that there were significant differences existed among the hybrids for all the characters. The genetic variability studies indicated that the material used in the present study possessed sufficient variability which gives ample scope for improvement through selection procedures. High heritability accompanied by high genetic advance was observed in case of plant height, number of monopodia, number of sympodia, relative water content, specific leaf weight, crop growth rate at peak flowering stage, crop growth rate at boll formation stage, crop growth rate at maturity stage, boll weight, seed index and lint index indicating the role of additive gene action in the inheritance of these traits and directional selection could be rewarding. The correlation and path analysis revealed that lint yield per plant had high positive direct effect coupled with high significant positive correlation. The other important traits identified were boll weight and number of sympodia per plant but they exerted direct effects at lower magnitude. Majority of the traits studied exerted prominent positive indirect effects via lint yield per plant. Further it was also observed that important fibre quality parameters like ginning out-turn, 2.5% span length and bundle strength showed undesirable association with the above traits and also among themselves. So care should be exercised in simultaneous improvement of these traits without sacrificing fibre quality, since the cotton is valued for its lint. Estimates of variance due to gca and sca and their ratios revealed the importance of non-additive gene action for all the traits studied. Non-additive component may be exploited through heterosis breeding. It also helps in varietal adaptability. Among the 19 parents involved, the lines RAC 99152 followed by RAH 178-4, NAWAB and RAH 97-612 and in testers SC 68 followed by SC 7- IPS and SC 40 were identified as potential general combiners for important yield component traits. These parents may be utilized in further breeding programmes for varietal improvement. Combining ability studies revealed that, it is not possible to find a definite trend for all the traits in hybrids based on gca effect of parents and sca effect of resultant hybrids. Most crosses with high sca effect involved parents either with high × low , low × high or low × low combiners with a few exceptions of high × high general combiners. These hybrids are likely to produce desirable transgressive segregants which may be studied through biparental mating or diallel selective mating system or any other form of recurrent selection. Based on per se performance, high sca effect and standard heterosis, the top specific cross combinations identified for seed cotton yield and other component traits were RAH 370 × SC 31 and RAH 178 × SC 40. This suggested the possibility of direct utilization of these hybrids for commercial exploitation after thorough testing over larger number of diversified environments and seasons. The progeny of these crosses may be further advanced to isolate superior segregants in further generations or pedigree breeding to combine not only seed cotton yield but also fibre quality of the derived lines.encotton, yields, planting, biological phenomena, sowing, crossing over, genetics, additives, developmental stages, heterosisINTRA- HIRSUTUM, HYBRIDS, COTTON, Gossypium hirsutum L.Thesis