COMBINING ABILITY AND GENETIC DIVERGENCE IN COTTON ( G. barbadense L.)

Abstract

This experiment was conducted in order to estimate general and specific combining abilities effects and genetic divergence for yield and quality characters using the line x tester mating design. Seven lines and four testers along with their 28 crosses of (Gosssypium barbadense L.) were evaluated for yield and fiber characters at Sakha Agric. Res. Stat. during 2018 growing season. Analysis of variance revealed significant differences among the genotypes, parents and crosses for all studied characters, indicating the presence of considerable amount of genetic variability among the evaluated genotypes. The variance due to parents versus crosses was also significant for most studied characters indicating that significant heterosis could be expected incrosses for these characters and comparison will be much relevant. The variance due to males and females were also significant for most studied characters and majority than the variance due to parents (lines and testers), these results indicated that the experimental materials possessed considerable variability and the two types of combining ability were involved in the genetic expression of these characters. However line vs. tester showed highly significant differences for most studied traits, showing theimportance of both additive and non additive variance gene effects. Among the female parents (testers) Karshenky2 was the best combines for earliness index and micronaire reading. Giza 94 was the best general combines for earliness index , most yield and fiber characters. Giza45 and Giza 86 were predicted to be best general combines for fiber characters.While, Giza 93 has positive and significant general combining ability (GCA) for all the studied yield traits and fiber strength. The cross combinations Giza 86 x Giza 94 and Giza 93 x Giza 94 showed significant positive SCA values for boll weight, seed index and lint index. The dissimilarity coefficients among eleven cotton genotype corresponding to 55 possible comparisons showed that about 95% of the values were significant as Chi squares values. The eleven cotton parental genotypes evaluated in this study were grouped into five major clusters by using hierarchical clustering method on the basis of dissimilarity among parents and contribution of evaluated characters. The inter cluster distance was higher than the intra cluster indicating wide genetic divergent among the genotypes. The female parents Kar2, Suvin, Giza89*p s6 and Giza94 grouped at three wide clusters and divergent distance from each others. The extra-long varieties Giza 96, Giza 93and Giza 92 grouped at the same cluster and closely related with Giza 45 (cluster5) and divergent distance with the other groups. The male parents Giza 85, Giza90 and the female Kar2 grouped at the same cluster (1) and characterized as a good combiner for earliness index. The Egyptian variety Giza94 and the Indian genotype Suvin formed unique two groups (clusters 2 and 4) and pose most genes which controlling general combining ability for yield traits. The 36 genotypes were grouped into 12 major clusters based on relative dissimilarity among genotypes. The distribution of parental genotypes and their F1 heterozygous in dendrogram reflects a broad parallelism between divergence distance, general and specific combining ability. Parents for hybridization could be selected based on large inter cluster distance to isolate useful recombinants through segregates