genetic studies in upland cotton (gossypium hirsutum l.) ii. general and specific combining ability

the present experiment was carried out to assess the general combining ability (gca) and specific combining ability (sca) of six important commercial cultivars of gossypium hirsutum l. of venezuela, viz., ‘deltapine 16’, ‘tamcot-sp-21’, ‘cabuyare’, ‘stoneville’, ‘ospino’ and ‘acala 90-1’ and their 15 f1 hybrids, respectively. the data were analyzed using griffing’s model i method ii. significant differences were found for all traits evaluated, except for seeds per boll and bolls per plant. combining ability analysis of variance revealed significant differences for gca and sca effects among the parents and hybrids for almost all traits except for seed cotton yield ha-1 and fiber % for gca and boll set, seed yield, and fiber % for sca. the results suggested the presence of additive and non-additive gene action for almost all of the traits. the ratio gca/sca ranged from 0.59 for fiber fineness to 5.14 for plant height. cultivars with the best (desired) gca effects were cv. cabuyare for blooming initiation, seed yield, and fiber fineness; stoneville for plant height, stem diameter, number of fruit branches, number of set flowers, and boll weight; tamcot-sp-21 for boll set and fiber fineness; deltapine 16 for plant height, 100-seed weight and fiber length; ospino for fiber strength. also, the results revealed that stoneville was the best general combiner for most of the traits. finally, the correlations among gca effects of the parents showed negative and significant associations of boll set with plant height and positive and significant associations of fruit branches with plant height, boll weight, and number of set flowers; of set flowers with plant height and boll weight; and of plant height with stem diameter.