SOURCES OF RESISTANCE TO PATHOTYPE QCC OF PUCCINIA-GRAMINIS F SP TRITICI IN BARLEY

The occurrence of a wheat stem rust (Puccinia graminis Pers.:Pers. f. sp. tritici Eriks. and E. Henn.) pathotype (Pgt-QCC) with virulence for the Rpgl gene in barley (Hordeum vulgare L.) necessitated the search for resistant barley germplasm. From preliminary screenings of over 18000 barley accessions, 13 lines were identified as possessing resistance to pathotype QCC: 'Diamond', 'Hietpas 5', Q21861, PC 11, PC 84, PC 249, PC 250, CI 5541, PI 452406, PI 452421, PI 477843, PI 477854, and PI 477860. This study was conducted to further characterize the reaction of the selected lines to pathotype QCC. The reaction was assessed by evaluating infection types at the seedling stage and infection responses at the adult plant stage in the greenhouse, and by evaluating disease severity and infection responses at the adult plant stage in the field compared to susceptible cultivars. Most lines exhibited low to intermediate infection types at the seedlings stage and moderately resistant to moderately susceptible infection responses at the adult plant stage in the greenhouse experiments. Among the selected lines, Q21861 exhibited the highest level of resistance at both the seedling and adult plant stages. These lines may provide an adequate level of resistance to pathotype QCC for cultivar development.