Method for Rapid Production of Fusarium oxysporum f. sp. vasinfectum Chlamydospores

A soil broth made from the commercial potting mix SuperSoil induced rapid production of chlamydospores in several isolates of Fusarium oxysporum. Eight of 12 isolates of F. oxysporum f. sp. vasinfectum produced chlamydospores within five days when grown in SuperSoil broth. The chlamydospore-producing isolates included four known races and four genotypes of F. oxysporum f. sp. vasinfectum. The SuperSoil broth also induced rapid chlamydospore production in three other formae speciales of F. oxysporum: lycopersici, lactucae, and melonis. No change in chlamydospore production was observed when variations of the SuperSoil broth (no glucose added, no light during incubation, and 60-min autoclave times) were tested on six isolates of F. oxysporum f. sp. vasinfectum. Although chlamydospore yields in SuperSoil broth without glucose were comparable to a published soil broth, SuperSoil broth was easier to make and its yields were more consistent. One isolate of F. oxysporum f. sp. vasinfectum race 4 consistently produced greater than 10 million chlamydospores per 50 ml of inoculated SuperSoil broth. SuperSoil broth may be useful for generating chlamydospores for studies of F. oxysporum and similar species in approximately the same time period as production of conidia in liquid or agar media.