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For development of high yield wheat cultivars, this study was conducted to estimate the general combining ability (GCA) of parents, specific combining ability (SCA) of hybrid progenies, heritability and heterosis of grain yield and some agronomic traits. A partial diallel crosses which obtained in a set of six wheat genotypes were sown in randomized complete block design at Gachsarann agricultural research station in 2013-14 growing season under dryland condition. The results of this study revealed a significant difference among the genotypes for all of the traits that indicating considerable genetic variation. Significant effects of GCA and SCA indicated role of additive and non-additive gene action in the control of all considered traits. The mean square ratio of GCA to SCA and Baker genetic ratio showed a preponderance of non-additive gene action for all of the studied traits. Broad-sense heritability was high (0.67-0.99) for all of them, which indicated the role of genetic factors compared with non-genetic factors for controlling of these traits. Narrow-sense heritability was low to moderate (0.06–0.37). Among the parents, Koohdasht was the best general combiners for early growth vigor, days to maturity, spike length, peduncle length, flag leaf extrusion and grain yield. The Koohdasht × DAMARA-6 hybrid showed the best specific cross for days to heading, days to maturity, grain filling period, plant height, chlorophyll content, canopy temperature, grain length and grain yield. These hybrids showed positive and significant heterosis for grain yield, chlorophyll content and grain length and negative heterosis for plant height. It is expected to produce desirable segregants and could be exploited successfully in wheat improvement programs. In addition, because of preponderance of non-additive gene action for studied traits, particularly in the early generations, efficiency of genetic selection was low and selection for genetic improvement of these traits must be retraced in advanced generations.

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In order to estimate the components of genetic variance and general and specific combining abilities of maize lines, an experiment was done using 8 S6 inbred lines as female parents and 2 male inbred lines as testers consisted of K1264/5-1 (early mature) and K3615/1 (late mature) using line by tester mating design based on randomized complete block design with three replications in two different conditions (Salt stress with Ec=5 dsm-1 and non-salt conditions) in research field of graduate university of advanced technology (Kerman, Iran) in 2014. Analysis of variance results showed significant differences among inbred lines for some of measured traits in both salt and non-salt conditions. Significant differences observed for line × tester mean-squares in non-salty condition for all measured traits except days to silking and physiological maturity. In salt stress condition, just for leaves number per plant and days to silking, line × tester effects were not significant. Additive variance for days to silking and physiological maturity in non-salt condition was more than dominant variance, therefore the additive to non-additive variance ratio was more than 1 and indicating emphasis on this matter too. Inbred line L6 had a significant positive GCA and the highest grain yield with 1455.785 and 789.107 kg/ha in non-salt and salt stress condition, respectively. The crosses (L4×T1=428.460 and L7×T1= 438,345) in non-salt condition and (L3×T1=438.345) in salt stress conditions had a positive significant specific combining ability. Finally, from all existed variation, the lines and line × tester effects were more important than tester effects that indicates transmission of diversity from lines to hybrids.