HETEROSIS AND COMBINING ABILITY OF SOME EGYPTIAN COTTON GENOTYPES

Half diallel cross among 6 Egyptian cotton genotypes (Gossypium barbadense L.) was done in 2016 season which produced 15 F ₁ crosses seeds. Parents and their crosses were evaluated in field trial during 2017 season using randomized complete block design at Sids Research Station of Beni-Suef Governorate (ARC) to explore general and specific combining abilities effects of parents and crosses and heterotic pattern of the cross combinations. Results showed that genotypes, parents, crosses and parent versus crosses exhibited significant or highly significant mean squares for all studied traits. Mean squares due to GCA and SCA were significant for all studied traits. Parent Karashanky recorded desirable mean performance for days to first boll opening, number of bolls/plant, seed cotton yield/plant and lint yield/plant. The F₁ cross (Giza 90 x Giza 94) performed better than all cross combinations for days to first boll opening (119.63 day), boll weight (3.17g), seed index (9.57g) and fiber strength (10.33PI). The maximum number of cross combinations that recorded positive highly significant useful heterosis values relative to mid and better parents were observed in boll weight and lint yield followed by seed cotton yield, lint index, number of bolls per plant and seed index. The (Giza 90 x Giza 94), (Giza 95x C.B58 ×G 90) and (Karashanky x [ (Giza83 x Giza80) x Giza89] x Aust.)) cross combinations exhibited highly significant positive heterosis over both mid and better parents and also showed significant SCA effects for yield and most of its component. The parents (Giza 90) and ([(Giza83 X Giza80) X Giza89] X Aust.)) were the best combiners for earliness traits, whereas (Giza 94) was the best combiner for fiber length, fiber strength and uniformity ratio. Variances due to SCA were higher than those of GCA for all studied traits. The ratios of GCA/ SCA were less than unity for all studied traits, while σ²D values were higher than σ²A for all studied traits except seed index. These results may indicate the important role of non-additive gene action in inheritance of these traits