Abstract
Thirteen isolates of Monosporascus cannonballus POLLACK and UECKER collected from melon plants with root rot symptoms in various districts of Japan were compared for their morphological characteristics and pathogenicity. The fungi were isolated from the roots of melon plants, basal stems 10cm of above the ground, but not from stems above 20cm, fruits and seeds. Melon plants planted in the infected field soils stored for 1〜5 years under laboratory conditions showed root rot symptoms, and fungi were isolated from the roots. Recent outbreaks of melon root rot caused by M. cannonballus were discussed.
