Abstract
Among the 10 kinds of plant extracts tested, celery extract was the best for chlamydospore formation by Fusarium oxysporum f. sp. niveum. Addition of 0.03M Na2SO4 to 2% celery extract greatly increased the number of chlamydospores produced. Light was inhibitory to chlamydospore formation in celery extract plus Na2SO4. The medium supported chlamydospore formation by five other formae speciales of Fusarium oxysporum, and two isolates each of Fusarium roseum and Fusarium solani. Chlamydospores of F. oxysporum f. sp. niveum produced in this medium germinated 87 to 98% in 6hr and caused 89 to 100% death of watermelon seedlings.
