Biplot analysis of diallel cross data for infection type of wheat stripe rust

Dialer crosses have been used in genetic research to determine the inheritance of important traits among a set of genotypes and to identify superior parents for hybrid or cultivars development. Genetic control of infection type of stripe ruts was studied in a half-diallel design using six wheat cultivars, Tiritea (a susceptible check), Tancred, Kotare, Otane, Karamu and Briscard. These cultivars and their 15FlS. were evaluated by three stripe rust path types 7EI8A-, 38EOA + and 134E134A +. For each pathotype a randomized complete block design with three replications was conducted with 21treatments. The biplot method was arranged by the first two principal component (PCs). Analysis of variance showed significant differences between 21 treatments for infection type. Changing the path types caused reversal of the domillance in most of the crosses. Briscard for the path types 38EOA+and 134E134A+, and Kotare for the pathotype 7E18A- had the highest GCA effects for infection type, so they can be used in breeding programs for development of resistant cultivars to stripe rust. The highest negative SCA was observed in crosses of Kotare x Karamu for 7EI8A-, Tiritea x Otane for 38EOA+ and Briscard x Kotare for 134E134A+. These SCA values indicate the presence of dominance for the lower infection type. The results indicated that infection type, as a component of resistance is under genetic control and seiection for this character would be effective in wheat breeding programs.