Abstract
Crucifer strains of Olpidium brassicae were isolated from the soil in cabbage fields for the first time in Japan. Initial bulk-cultures developed resting spores, but single-sporangium isolates (CBG-1 to 5 and YR-1 to 4) did not. Resting spores formed after mixed inoculation with the isolates. The results confirmed the assumption by Sahtiyanci (1962) that Pleotrachelus brassicae (=O. brassicae) is hetellothallic. On the other hand, of five single-sporangium isolates of noncrucifer strains from fields of welsh onion (WOms-3), tobacco (TAK-1), lettuce (LE-4, WT-1) or soybean (F-1), three (WOms-3, LE-4, WT-1) were a vector of lettuce big-vein and developed resting spores without mating. The distribution of resting spores in their first generation varied depending on the infection sites and host plants. These results indicated that the manner of resting-spore formation differed between crucifer and noncrucifer strains, suggesting that both strains were distinct species as suggested by Sahtiyanci (1962).
