Estimation of combining ability and gene action for yield contributing traits in spring barley under normal and salinity conditions

Large proportion of the total land area in the world is salt-affected. Breeding for high yielding-varieties under normal and salinity conditions present an important solution for increasing the production and reduce the gap between production and consumption of cereal crops. Half diallel analysis among eight diverse spring barley genotypes was performed to provide information on general and specific combining ability, gene action and heritability for different agronomic traits under normal and salinity conditions. The used genotypes were four commercially cultivars (Giza 123, Giza 126, Giza 132 and Giza 2000) and the other four were introduced from ICARDA (Australian, CHK 38, CHK 2 and CHK 53). The parents were grown and crossed during 2014-2015 in the Experimental Farm of Faculty of Agriculture (Ghazala), Zagazig University, Egypt. In second season the derived seeds from crosses and parents were sown at two distinct locations. The first was in Ghazala as normal condition and the other was under salinity condition in the Experimental Farm of Desert Research Center, Ras-Sudr Research Station, South Sinai, Egypt, with salinity in irrigation water and soil containing 4500 ppm and 5535 ppm, respectively. Both experiments were in randomized complete block design with three replications. The measured traits were; plant height (cm), spike length (cm), number of spikes per plant, number of grains per spike, grain weight per spike (g), 100 grain weight (g) and grain yield per plant (g). Diallel analysis was performed for each environment separately. Analysis of variance indicated that there were highly significant differences between parental genotypes and theirs F1 crosses for all studied traits. General (GCA) and specific (SCA) combining ability effects were highly significant under both conditions for all traits. The genotypes; P3 (Australian) and P6 (CHK 53) showed good performance as well as good GCA effects under salinity condition, while P4 (CHK 38) and P8 (Giza 2000) under normal one and P2 (Giza 126), P5 (CHK 2) and P7 (Giza 132) under both conditions. The cross combinations; P3×P5, P3×P8 and P5×P8 exhibited good performance and significant positive SCA effects for grain yield and its attributes under salinity, while P2×P7, P3×P4, P4×P7, P5×P7 P6×P7 and P7×P8 under both conditions. The variance due to SCA was higher than that of GCA for all the traits except plant height and number of spikes per plant under salinity condition and 100 grain weight under normal condition. The components of genetic variance suggested more contribution of the dominance effects in the inheritance of the studied traits compared to additive ones. Narrow sense heritability values changed from environment to another, it ranged from low to moderate (4.62% to 31.96). The low values due to excess of dominance effect as well as great effect of the environmental factors in the genetic control of the studied traits. Wr-Vr graphs showed high degree of genetic diversity for parents with different degrees of dominance and different distribution of dominant and recessive alleles in the parental material for all traits under both conditions.