Document Type : Original research
10.12816/ejpb.2021.220555
Abstract
Combining ability estimates for yield ,its components and some fiber properties of the Egyptian cotton species were the ultimate aim of this investigation. The genetic materials used in the present study included six cotton genotypes and their 45 double crosses. In 2020 growing season, these genotypes were evaluated in a field experiment at sids Agricultural Research Station, Beni-suef Governorate for the following traits: boll weight (BW), number of bolls/plant (NB/P), seed cotton yield/plant (SCY/P), lint yield/plant (LY/P), lint percentage (LP), upper half mean (UHM), uniformity ratio(UR) ,fiber fineness (FF) and fiber strength (FS) . The results showed that the mean squares of genotypes were highly significant for all its components except for boll weight (BW) and lint percentage (LP) traits, the partition of crosses mean square to its components showed that the mean square due to 1-line general, 2-line arrangement, 3-line arrangement and 4-line arrangement were either significant or highly significant for most studied traits. This result suggesting the presence of the additive and non-additive genetic variance in the inheritance of these traits. The variety Giza 85 (P2) was the best general combiner for most studied yield component traits such as NB/P, SCY/P, LY/P and LP.Also, the variety S106 (P6) showed a positive desirable value of general combining ability for the same previous traits and was also the best combiner for UHM. Concerning the 2-line interaction effect, (S212), (S213), (S224), (S226) and (S246) showed positive (desirable) effects for most yield components. Moreover, the best combinations for UHM, UR and FS were shown by (S246), (S234) and (S225), respectively. On the other hand the 3-line interaction effect cleared that the combinations (S3124),(S3126),(S3136)and (S3246) showed great positive (desirable) effects for all yield and yield component traits In the same time, (S3125), (S3134) and (S3256) revealed the best combinations for FS.Beside (S3125), (S3126) and (S3146) for UHM as well as [(S3125) and (S3346)] for UR property. Concerning, the 4-line interaction effect revealed thatthe best double cross combinations for SCY/P, LY/P was (S42456). Moreover,(S41356), (S41246) (S41235), and (S41346) were the best double cross combinations for NB /P, LP, UHM, UR and (FS) respectively. With respect to the specific combining ability effects t2 (ij) (..) showed that the best double cross combinations forB.W, SCY/P, LY/P and FF was t2(15)(..). The combinations t2(23)(..) and t2(26)(..), were the best combinations for NB./P, LP, UHM, UR and FS traits, respectively. It seams that the combinations [(P1×P3) x (P2×P5)], [(P1×P3)x(P4×P6)] and [(P2×P5)×(P4× P6)] appeared to be the best promising double crosses for breeding toward most studied yield traits potentiality. As for gene action, the magnitudes of dominance genetic variance (σ2D) were positive and larger than those of additive genetic variance (σ2A), for all studied traits except of BW, LP, FF and FS. Besides, the epistatic variances, additive by additive (s2AA) and additive by dominance (s2AD) were negative and considerable magnitude for all studied traits except for the same four previous traits BW, LP, FF and FS. Besides, the epistatic effects of 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, LP, FF and FS.Therefore, it could be recommended that production of double crosses to be involved in the selection breeding programs is the desirable way for improvement of these traits.
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