GENETIC ANALYSIS OF SOME BREAD WHEAT CROSSES UNDER NORMAL AND LATE SOWING CONDITIONS

Abstract

This study examined the nature and magnitude of gene action for yield and its contributing characters in bread wheat (Triticum aestivum L. em. Thell) to determine suitable breeding method for future wheat improvement programs. Seven parents along with their 21 F1's were evaluated under two sowing dates, i.e. 15th of Nov. (the recommended sowing date) and 5th of Dec. (the late sowing date) at the Experimental Farm of Fac. of Agric., Ain Shams Univ., Shalakan, Kalubia Governorate during 2014/15 growing season. The results revealed that mean squares due to sowing dates, genotypes and genotypes x sowing dates interaction were significant for most of studied traits. Delaying sowing date to December reduced means of all the studied traits compared to the recommended sowing date. The two parental genotypes; Cham 4 and IB 18 as well as the four crosses; Misr 1 x Cham 6, Cham 4 x Cham 6, Misr 1 x IB 18 and Cham 4 x IB 18 indicated their tolerance to late sowing date. Results showed that there is a desirable heterobeltiosis for grain yield plant-1 and most of evaluated traits. The highest positive heterosis value was 30.40% in cross Cham 6 x L606 for flag leaf area at recommended sowing date followed by 17.10% in the cross Sids 12 x Cham 4 for 1000- kernel weight and 13.26% in the cross Sids 12 x IB 18 and 12.87% in the cross Cham 4 x Cham 6 for grain yield plant-1. However, the highest negative heterosis value was -5.49% in the cross Sids 12 x Misr 1 for days to heading at the recommended date. Estimates of general and specific combining ability mean squares indicated the importance of both additive and non-additive genetic effects in the inheritance of the studied traits with few exceptions. However, the additive genetic effects were more important than the nonadditive ones in the inheritance of days to heading and plant height at both environments as well as grain yield plant-1 under stress conditions. Meanwhile, the non-additive genetic effects were more important than the additive ones in the inheritance of flag leaf area, number of kernels spike-1 and 1000-kernel weight under both conditions as well as number of spikes plant-1 under stress conditions. The results of applying combining ability analysis indicated that the two parents; Cham 6 and IB 18 were found to be the best general combiners for most of the investigated traits under normal and late sowing conditions. The best specific combiner crosses for flag leaf area, no. of spikes plant-1, no. of spikelets spike-1, no. of kernels spike-1, 1000-kernel weight and grain yield plant-1 under normal and heat stress conditions were Cham 6 x L606 and IB 18 x L606.