GENETIC PREDICTION OF STRIPE RUST RESISTANCE THROUGH CROSSING ANZA A+ TO SIX EGYPTIAN WHEAT CULTIVARS

Anza A⁺ was crossed with 6 Egyptian wheat cultivars (Triticum aestivum, L.). These cultivars, F₁, and F­₂ were tested under greenhouse conditions at seedling stage against pathotype (race) 230E18 of Puccinia striiformis. The cultivars and F₁ possessed a susceptible (S) phenotype. The F₂ populations were segregated into two gene pairs. The dominance tend direction of susceptibility. The resistance genes were recessive. On the other hand, at adult stage under field conditions against races mixture of the pathogen, Anza A⁺ possessed (R) phenotype, the F₁ showed resistance of each all crosses. The F₂ populations were segregated with 4 crosses (2 and 2) fitted the expected ratios 15 (R): 1(S) and 3 (R): 1(S). The other two crosses i.e., Anza A⁺ /Giza 168 and Anza A⁺ / Sakha94 appeared no segregated and dominance of resistance. The cultivars Giza 168 and Sakha94 may have the adult plant resistance gene Yr A⁺ under filed conditions. These findings confirmed that this gene is an effective under the Egyptian environmental conditions. Results obtained showed that partial stripe rust resistance in the tested wheat cultivars was controlled by one ore two gene pairs in most cases at seedling and adult stages. These results indicated that the selection for partial resistance materials in the early generations was possible while delaying it to late ones is more effective, due to the important role of dominance effect in the expression of this trait.