Abstract
Pythium graminicola was predominantly isolated from diseased rice seedlings at the 2-3 leaf stage with symptom of acute wilt. The disease occurred at middle and latter growth stages of rice seedlings grown in three different soils in nursery flats. Pathogenicity studies indicated that P. graminicola produced acute wilt symptom on rice seedlings at the 2-3 leaf stage similar to that characteristically seen in nursery flats when rice seeds were sown in soil artificially infested with a small amount of hyphae of the fungus or when rice seedlings at the 2 leaf stage were inoculated with zoospores. In addition, P. graminicola caused pre-emergence seedling rot when rice seeds were sown in soil artificially infested with a large amount of hyphae of the fungus or when germinated seeds were inoculated with zoospores. From these results, P. graminicola is considered to be the causal agent of damping-off of rice seedlings in nursery flats.
