Black Choke Disease of Warm Season Grasses Caused by Ephelis japonica in Japan and its Epiphytic Features

Abstract

The causal fungus of black choke disease in various C4 warm season grasses was collected from places mainly in Ishigaki Island, the most southern region of Japan. The fungus was found on 19 species of 14 genera of C4-grasses such as Brachiaria, Chloris, Chrysopogon, Cynodon, Digitaria, Echinochloa, Eragrostis, Eriochloa, Imperata, Leptochloa, Miscanthus, Panicum, Paspalum, and Pennisetum, including turfgrasses and forage crops. The fungus colonizes flowering heads and makes them mummified in appearance with the panicles attaching to each other. The color of the mature stromata ranges from grayish-white to black. Leaf surfaces of some grasses are colonized by the fungus, producing white streaks of hyphae. Many colorless, needle-shaped conidia of 10-25 × 0.5-1 µm are produced on infected tissues. The fungus was identified as Ephelis japonica based on the morphologies and molecular characteristics. Epiphytic features of E. japonica were examined using infected and uninfected Paspalum thunbergii clones from which the fungus was eradicated by treatment with a systemic fungicide. Hyphae colonized the surface of leaf primordia only in infected plants, a feature shared with some of the closely related Balansia spp. The potential for utilizing E. japonica to confer insect and disease resistance in turfs and forage crops was discussed.