Survey and evaluation of Ustilago trichophora as bioherbicidal agent for Echinochloa species

摘要

Biological control of an important weed, Echinochloa crus-galli var. crus-galli, using a smut pathogen, Ustilago trichophora, was investigated under greenhouse conditions. Sixty-four Echinochloa plants (E. crus-galli var. crus.galli, E. crus-galli var. praticola, E. crus-galli var. formosensis, E. oryzicola and E. utilis) with smut galls caused by U. trichophora on kernels, leaf sheaths or culms were collected, from 54 locations in 21 prefectures in Japan. Each single-teliospore isolate of U. trichophora, obtained from galls on diseased plants, produced galls on E. crus-galli var. crus-galli after injection of a suspension of yeast-like budding cells of each isolate into the host leaf sheaths. Galls appeared on various parts of host plants, especially on leaf sheaths, leaf blades and culms, and occasionally on kernels. A monocellular strain was established from a colony produced on a potato dextrose agar plate by streaking a single teliospore isolate. The strain was purified by repeating this procedure five times. When suspensions of yeast-like budding cells of each monocellular strain were sprayed on second-leaf stage E. crus-galli var. crus-galli plants, all strains produced galls. Of these, three strains produced galls on more than 70% of plants, particularly on the base of the culm, and inhibited growth, occasionally killing plants. These results indicate that U. trichophora has high potential as a mycoherbicidal agent for Echinochloa weeds.