INHERITANCE OF RESISTANCE TO STRIPE RUST IN SEVERAL COMMERCIAL CULTIVARS AND SELECTED ELITE GENOTYPES OF WHEAT FROM FARS PROVINCE

This study was carried out to identify the number of resistance genes and mode of inheritance to yellow rust caused by Puccinia striiformis f. sp. tritici among selected elite genotypes of 2000-2002 and several commercial wheat cultivars. The wheat elite genotypes and cultivars were crossed to susceptible parent Avocet S. F1 populations were grown to produce F2 and F3 generations in the successive years. For genetic analysis, two F3 families from each cross at adult plant stage in the field and one F3 family of cross Bahar/Avocet S at seedling stage in the greenhouse along with parents, some of the commercial and control cultivars were examined to Puccinia striiformis f. sp. tritici pathotype 166E138A+ (that was the dominant yellow rust race in Fars province). Genetic analysis showed that elite genotypes including M-79-4, M-79-5, M-79-18, M-80-13, M-80-20, M-81-5, and the cultivar Darab 2, and elite genotypes S-78-11 and S-79-10 each had one adult plant resistance gene. The elite genotypes M-80-6, M-80-12, M-81-8, M-81-13 and M-81-15 were shown to confer two adult plant resistance genes. The resistance in elite genotypes M-79-17, M-81-18, M-80-4 and M-80-5 and cultivar Nik­Nejad each was controlled by two dominant genes at least one of which operated at the seedling stage. The cultivar Bahar was shown to have one seedling and one adult plant resistance gene. The elite genotypes M-79-13 and M-81-3 and the cultivar Star were shown to lack any resistance genes at both seedling and adult plant stages. Past experiences with wheat rusts indicate that relying on single resistance genes particularly those with seedling resistance genes that were also identified in some of the cultivars and elite lines in the present research are usually short lived and mostly encounter with the danger of breaking of resistance in a short period (4-5 years) of time. Deployment of resistance genes of Nik­Nejad cultivar and those elite lines that carried two adult plant resistance genes is recommended in breeding programs in order to produce resistant cultivars with more longevity.