The EUCARPIA Multi-site Rust Evaluation − 2013 Results

A set of 16 Italian (Lolium multiflorum), 4 hybrid (L. boucheanum) and 34 perennial ryegrass (L. perenne) cultivars were sown at 21 sites in 11 European countries. The cultivars were grown as rows in a completely randomized block design with four replicates. Rust incidence was scored in the year of seeding using a scale based on an estimation of the percentage of leaf area affected. Crown rust (Puccinia coronata f. sp. lolii) was the most frequently observed rust species. Compared to the previous trials, stem rust (P. graminis f. sp. graminicola) was reported more frequently, i.e., at eight sites for perennial ryegrass but also at five sites for Italian ryegrass. At most sites, there was a highly significant difference in crown and stem rust resistance among Italian and perennial ryegrass cultivars. The ranking of the Italian/hybrid and perennial ryegrass cultivars in terms of crown rust susceptibility was very consistent across the different sites. Moreover, the ranking of the mean crown and stem rust susceptibility of the cultivars was highly correlated with the corresponding ranking of the cultivars in the 2001, 2004, 2007 and 2010 trials, respectively. There is no evidence that crown and stem rust resistance of an individual cultivar was overcome by the rust pathogen over the 12 years of experimental observations.