Susceptibility to Rust (Puccinia Sp.) in Cultivars of Italian and Perennial Ryegrass Grown in Two Locations of Italy

A large set of foreign varieties of Italian ryegrass (Lolium multiflorum) and perennial ryegrass (L. perenne) were evaluated for their response to natural rust infection in two Italian locations (Lodi in the north; Perugia in the centre of the country) at three-year intervals in 2001, 2004 and 2007, to acquire information on novel germplasm for Italy and verify any spatial and temporal variation in the varietal response to the disease. Crown rust (caused by Puccinia coronata) on Italian ryegrass and stem rust (caused by P. graminis) on perennial rygrass were consistently recorded in appreciable amount (average susceptibility score > 2.0 on a 1-9 scale). Vice-versa, crown rust on perennial and stem rust on Italian ryegrass seldom affected appreciably the crop. Strong interactions of variety response (to the prevailing pathogen) with locations and years of evaluation were observed in both ryegrasses. Subsequently, the repeatability of results between locations, or between years within locations, as measured by rank correlations of variety scores, was sometimes only moderate or low. However, despite such interactions, a few promising varieties were identified in each species with consistently low susceptibility across evaluation environments, which deserve further investigation for a possible direct utilisation, or as donors of useful genes for breeding purposes.