摘要：Present study aimed to use recurrent selection method to cross some cotton genotypes for population improvement for some important traits; such as high yield, earliness and good fiber quality, under late planting date. The mean value (68.83 g) of hybrid No. 4 for seed cotton yield/plant was highly significant compared to its direct parents; P_1 and P_5 (43.85 and 51.51 g, respectively). For earliness index, three hybrids No. 1, 2 and 3 were highly significant (90.23, 88.85 and 87.26 %) compared to the best original parent (82.91 %) and commercial variety G. 86 (80.91 %). In hybrids, the estimates of GCV (9.47, 3.39 and 5.51) for earliness index, fiber length and fiber strength, respectively, and the estimates of PCV (9.72 and 3.60) for earliness index and fiber length, respectively, were higher than that obtained in F_6 generation. Heritability values; in hybrids, for earliness index, fiber length, uniformity index and fiber strength (94.99, 88.18, 31.25 and 81.50 %, respectively) were higher than the recorded values in the F_6 generation (72.92, 84.9, 10.26 and 12.80 %, respectively). The observed gain of the best five selected hybrids for seed cotton yield was ranged from 4.51 to 26.37% for seed cotton yield and from -8.08 to 3.86 % for earliness index compared to the better parent. While, observed gain values were ranged from 14.82 to 38.84% for seed cotton yield and from -5.83 to 6.41% for earliness index compared to commercial variety. Observed gain values for earliness index of two selected hybrids (No. 5 and7) and hybrid No. 4 were significant and highly significant, respectively, compared to commercial variety. For fiber length, the observed gain value of one hybrid No. 7 was highly significant compared to better parent and commercial variety. Pointed to fiber elongation trait, the observed gain value for hybrid No.5 was significant compared to commercial variety. In terms of micronaire reading, the observed gain value of hybrid No. 4 was significant compared to the better parent. Meanwhile, hybrid No. 6 and No.4 were significant and highly significant, respectively, compared to commercial variety. In addition for quantifying the level of polymorphism among two original parents, five direct parents and ten hybrids resulted from hybridization among the five direct parents by using EST-SSR and SSR markers. A total of three EST-SSR and nine SSR primers were used and the percentage of polymorphism was found to be 84.21 % for EST-SSR and 88.31 % for SSR markers.
