DOUBLE CROSSES ANALYSIS OF SOME ECONOMIC CHARACTERS IN EGYPTIAN COTTON

Abstract

The genetic materials used in the present study included six Egyptian cotton varieties Giza 85 (P1), Ashmouni (P2), Giza 75 (P3), Giza 80 (P4), Giza 86 (P5) and Giza 90(P6) and their corresponding 45 double crosses.These genotypes were evaluated in a field trial experiment at Sids Agricultural Research Station, Beni-suef Governorate through 2017 growing season for the following traits: boll weight (BW), bolls/plant (B/P),seed cotton yield/plant (SCY/P), lint yield/plant (LY/P), lint percentage (LP), fiber fineness (FF), fiber strength (FS), upper half mean (UHM) and uniformity ratio(UR). Results showed that the mean squares of genotypes were highly significant for all studied traits, the partition of crosses mean square to its components showed that the mean square due to 1-line general, 2-line specific, 2-line arrangement, 3-line arrangement and 4-line arrangement were either significant or highly significant for all studied characters.This result suggesting the presence of the additive and non-additive genetic variance in the inheritance of these traits .Concerning the two-line interaction effect, (S212),(S213),(S214),(S224) and (S245) showed positive (desirable) effects for most yield components and fiber quality traits. Also, the three-line interaction effect cleared that the combinations (S3124),(S3125),(S3126),(S3134),(S3136) ,(S3145) and ,(S3245) were the best combinations for most studied characters. Furthermore, the four-line interaction effect revealed thatthe best double cross combination for SCY/P, LY/P, UHM and UR was (S41245). Moreover,(S41236), (S41246), (S42345), (S42346) and (S43456) were the best double combinations for B/P, LP, FF, FS and BW, respectively. The parent Giza 85 (P1) was the best general combiner among this group of varieties for all yield and its components under study except BW and recorded desirable effects for all studied fiber quality traits.Also, Giza 86 variety (P5) was the best combiner for BW ,while Ashmouni variety (P2) was the best combiner for FF and Giza 90 variety (P6) was the best for FS. The specific combining ability effects t2(ij)(..) showed that the combinations t2(13)(..), t2(14)(..), t2(26)(..),t2(36)(..),t2(45)(..),t2(46)(..)and t2(56)(..) were the best combinations for SCY/P,LY/P and UHM , B/P,FS,FF,LP,BW,UR traits, respectively. Generally, from preivous results, it could be concluded that the combinations : [(P1 x P3) x (P2 x P4)], [(P1 x P3) x (P5 x P6)] and [(P2 x P4) x (P5 x P6)] appeared to be the best promising double crosses for breeding toward improvment most studied yield and fiber quality traits . Dominance genetic variance magnitudes (s2D) were positive and larger than those of additive genetic variance (s2A) for all studied traits except for BW and FS.Regarding epistatic variances, additive by dominance genetic variance (s2AD) showed negative and considerable magnitude for all studied traits except for BW. Moreover, additive by additive genetic variance (s2AA) showed negative and considerable magnitude for all studied traits except for BW,LP and FS traits. While, dominance by dominance genetic variance (s2DD) and additive by additive by additive genetic variance (s2AAA) showed positive and considerable magnitude for all studied traits with the exception of BW. It could be concluded that fiber properties and yield components were mainly controlled by epistatic variances; dominance by dominance (s2DD) and additive by additive by additive (s2AAA). This finding may explain the superiority of most studied double crosses than their parents in most of yield components traits. Therefore, it could be recommended that production of double crosses to involve in the selection breeding programs is the desirable way for improvement these traits. Heritability in narrow sense (h2ns %) ranged from 36.4% for LY/P to 84.2% for BW.