Abstract

Trifolium repens L. is widely grown in China as a lawn plant, forage and green manure crop. Investigations conducted in September 2022 revealed a leaf spot disease on T. repens with an 35% incidence (100 plants were investigated) in Qinghezhizhou Park, Haidian District, Beijing, China. Infected leaves showed water-soaked V-shaped yellow lesions that later turned brown and eventually led to the death of the affected leaves. Leaves displaying typical pathological symptoms were photographed and collected for pathogen isolation and identification. Symptomatic leaf tissues were excised from the margin between healthy and diseased areas, surface sterilized with 2% NaClO for 2 min and 75% ethanol for 30 s, rinsed three times with sterile water, and incubated on potato dextrose agar at 25℃. Six pure isolates were obtained by single spore isolation and were deposited in the Culture Collection of the Institute of Plant Protection, Beijing Academy of Agriculture and Forestry Sciences (JZB). The strain numbers of these six pure isolates are JZB3720003-JZB3720008. On potato carrot agar (pH = 6.5), colonies reached 55 mm in diameter after 7 days at 25℃ under a 12 h light/12 h dark photoperiod. Aerial hyphae were fluffy, appearing white to light gray, and the reverse side of the colony was fawn to dark. Conidiophores were brown, solitary, straight or slightly curved, separated, occasionally branched, 68 - 212 um. Conidiogenous cells were pale brown, solitary or opposite, geniculate, 12.2 - 26.7 × 4.7 - 6.8 µm (average: 19.0 × 5.6 µm, n = 20). Conidia were slightly verruculose, clustered, straight or slightly curved, or geniculate, narrowly ellipsoidal or fusiform, 2 - 3 (mostly 3) septate, basal and apical cells brown, middle cells dark brown with enlarged, 17.8 - 27.8 × 6.1 - 11.9 µm (average: 24.1 × 9.0 µm, n = 30). Morphologically these isolates resembled species belonging to genus Curvularia , especially the C. trifolii (Sivanesan. 1987). Genomic DNA of the six isolates w