Inheritance of Crown Rust Resistance in a Perennial Ryegrass Genotype of the Cultivar Arvella

Abstract

Crown rust, caused by Puccinia coronata f. sp. lolii is a common disease of perennial ryegrass (Lolium perenne) in Europe. To study the inheritance of resistance to crown rust, a resistant genotype of the diploid cultivar Arvella was crossed with a susceptible genotype of the cultivar Aurora to generate a F₁ population. Out of this population, two parents were selected on the basis of crown rust reaction and backcrossed with a susceptible Aurora genotype to generate two sets of F₂ populations. All parents, the F₁ and the two F₂ populations were screened for their response to three single-pustule isolates (SPI) of crown rust in a detached-leaf segment test under growth chamber conditions. Genetic analysis of resistance led to the identification of two dominant resistance genes. The first gene, LpPc4, conferred resistance to SPI A and K, but not to SPI F. The second gene, LpPc5, proved to be effective against SPI F and K, but not against SPI A.