Fungi pathogenic to ryegrass seedlings

Summary Fungi borne on or in ryegrass (Lolium spp.) seeds or invading ryegrass seedlings grown on field soils were isolated and identified. Selected isolates were tested to determine their pathogenicity to ryegrass seedlings. Seed-borne fungi were generally weakly virulent or non-pathogenic to ryegrass seedlings. Pathogenic seed-borne fungi includedChaetomium globosum Kunze: Fr.,Curvularia trifolii (Kauffm.) Boedijn, and species ofPenicillium Link andAspergillus Mich. ex Link. Species of fungi isolated from seedlings grown on field soils de pended on soil and temperature. Soil-borne fungi pathogenic to seedlings includedFusarium avenaceum (Fr.) Sacc.,F. culmorum (W. G. Smith) Sacc.,F. equiseti (Corda) Sacc.,F. oxysporum Schlecht.: Fr.,F. solani (Mart.) Sacc.,Pythium afertile Kanouse and Humphrey,P. debaryanum auct. non Hesse,P. irregulare Buisman,P. ultimum Trow, a sphaerosporangiatePythium sp.,Chaetomium globosum, Thanatephorus cucumeris (Frank) Donk,Trichoderma koningii Oudem., and aPhomopsis sp. Individual isolates of fungi differed in virulence to ryegrass seedlings, and ryegrass cultivars differed in susceptibility to seedling pathogens.