STUDY OF GENES EFFECTS AND COMBINING ABILITY IN SOME BREAD WHEAT GENOTYPES TO YELLOW RUST DISEASE

The knowledge of genetic characters of quantative and qualitative traits and their heritability in wheat (Triticum aestivum.L.), are the most important requirement for breeding high wheat yield varieties and disease resistance of this strategically crop. Yellow rust (strip rust) caused by puccinia striiformis f.sp.tritici is an important disease of wheat in many regions of the world. In Iran, the most severs epidemic years were 1993 and 1995. For this reason. 10 lines of wheat were studied to determine study of genes effect and combining ability in some of bread wheat genotypes to yellow rust disease. Ten parents' lines, F 1 were evaluated in a randomized complete block design with three replications in Mashhad, Torugh Agricultural Research center, two races of wheat 134E134A⁺ and 4EOA⁺were used. Latent Period (LP), Infection Type (IT) were measured in the field and Greenhouse. Analysis of for the combination indicated significant differences between races and genotypes. Diallel analyzed with method of Griffing and Haymans. The GCA and SCA for all traits were significant and showed that additive variance was more important. Test for validity of diallel hypothesis showed epistasis effects for all traits. Average degree of dominance ranged from partial to over dominance for resistance or susceptibility.