Italian ryegrass is widely cultivated for the production of forage, hay, and silage because of its high nutritional value and good palatability. Leaf spots caused by fungi pose a serious threat to forage crops. In order to expand the knowledge of fungi causing leaf spots in ryegrass (Lolium multiflorum) in Sichuan, Yunnan, Chongqing, and Guizhou of southwestern China, a comprehensive survey was undertaken from 2015 to 2022. The survey discovered that Epicoccum leaf spot (ELS) was a common and widespread disease, more serious at the late stage of growth (after late May). Symptomatic leaf samples collected from the four different provinces were analyzed, and a total of 202 Epicoccum isolates were obtained. Based on both multilocus phylogeny (ITS, LSU, TUB2, and RPB2) and morphology, 10 Epicoccum species were finally identified, including three novel species (E. endololii sp. nov., E. lolii sp. nov., and E. loliicola sp. nov.), six new host records (E. draconis, E. endophyticum, E. oryzae, E. plurivorum, E. thailandicum, and E. tobaicum), and an unknown species (Epicoccum sp.1). Pathogenicity tests showed that E. endophyticum, E. endololii, and Epicoccum sp.1 were nonpathogenic to Italian ryegrass, which were confirmed as endophytes in this study; the other six species could infect Italian ryegrass and cause leaf lesions to different degrees, of which E. draconis was more aggressive (P ≤ 0.05). Coupled with the isolation rates and geographical distributions of these species, it was found that E. plurivorum was the predominant pathogen in Yunnan while E. oryzae and E. tobaicum were the predominant pathogens in the other three provinces. This work provides an initial understanding of the taxonomy, virulence, and distribution of Epicoccum species associated with ELS in southwestern China and lays a solid foundation for the diagnosis in the field and scientific control of ELS on Italian ryegrass.
Keywords: Lolium multiflorum; diversity; identification; leaf spot; novel species of Epicoccum.