Combining ability in the F1 generations of diallel cross for yield and yield components in wheat

Eight parents of bread wheat (Triticum aestivum L.) were crossed in a full diallel fashion and their F1s were evaluated for combining ability for yield components at the experimental farm of Plant Breeding and Genetics Department, NWFP Agricultural University, Peshawar during 2001-03. The traits included number of fertile tillers per plant, grain yield per plant, number of grains per spike, grain weight per spike and 1000-grain weight. The results indicated significant differences among the parents for general combining ability (GCA) and crosses for specific combining ability (SCA) for all the characters studied. Reciprocal combining ability (RCA) was significant for all the traits except grain weight per spike. The GCA and SCA components of variance were significant for all the traits. However, the GCA component of variance was predominant indicating the importance of additive gene effects for number of grain per spike and grain weight per spike while for number of fertile tillers per plant, grain yield per plant and 1000-grain weight SCA component of variance was predominant indicating the importance of non-additive gene effects for these traits. Tatara was the best general combiner for grain yield per plant, grain weight per spike and 1000-grain weight. Khattakwal and Ghaznavi-98 were the best general combiners for number of fertile tillers per plant and number of grain per spike, respectively. The best crosses were, KW x PS for number of fertile tillers per plant, KW x GZ for grain yield per plant, Inq x ID for number of grain per spike, GZ x Inq for grain weight per spike, KW x Tkb for 1000-grain weight and Tkb x Tat for number of grains per spike, grain yield per plant and grain weight per spike. These best parents and cross combinations could be effectively utilized in wheat breeding for the improvement of yield components and thus their incorporation in further breeding program is suggested. The overall study reveals the importance of both additive and non-additive genetic variability, which suggests the use of integrated breeding strategies, which can efficiently utilize the additive as well as non-additive genetic variability. Thus, use of diallel mating with recurrent selection could provide the better conditions for recombination and accumulation of desirable genes and is recommended for such type of study.