Recurrent Selection for Partial Resistance to Crown Rust in Oat

Abstract

Crown rust (caused by the fungus Puccinia coronata Cda. f. sp. avenae Eriks.) is a major disease of cultivated oat (Avena sativa L.). Partial resistance is a form of incomplete resistance characterized by a reduced rate of epidemic development and is potentially more durable than complete race-specific resistance. Four rapid cycles of selection for partial crown rust resistance were conducted in an oat recurrent selection population after the completion of the seventh cycle of selection for grain yield. The objectives of this research were to: (i) determine the effectiveness of rapid cycle recurrent selection for partial crown rust resistance; (ii) assess the indirect effect on grain yield, flowering date, and plant height; and (iii) estimate phenotypic and genetic correlations between traits and broad-sense heritabilities. Recurrent selection parents and check cultivars were evaluated in six environments. Four cycles of selection for partial resistance reduced the area under the disease progress curve (AUDPC) 42%. This increased resistance was not reflected in higher grain yields under moderate crown rust epidemics, but it produced a 4.7% grain yield gain per cycle in an environment with a severe rust infection. Selection for partial resistance indirectly delayed the flowering date by 2 d. Entry mean broad-sense heritability estimates were intermediate (41-64%) for AUDPC. Our results show the usefulness of rapid cycle recurrent selection as a population improvement procedure capable of effectively increasing the level of partial resistance to crown rust in a high-yielding oat population.