Submitted to: Journal of Cotton Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 28, 2012
Publication Date: February 28, 2013
Citation: Bennett, R., Davis, R. 2013. Method for rapid production of Fusarium oxysporum f. sp. vasinfectum chlamydospores. Journal of Cotton Science. 17(1):52-59.
Interpretive Summary: The Fusarium wilt fungus produces several types of spores, but uses a thick-walled spore called a chlamydospore to survive in soil. Therefore, to study the survival of the Fusarium wilt fungus in soil, one must work with chlamydospores. Some published methods for producing chlamydospores in the lab require several weeks or months to produce mature chlamydospores. Other methods are only adapted to small-scale production or produce inconsistent results. We developed a soil broth made from Super Soil, a commercial potting mix, capable of inducing chlamydospore production within one week. Eight of twelve Fusarium strains causing wilt disease of cotton, and five strains causing wilt disease of tomato, melon, or lettuce, produced large numbers of chlamydospores in Super Soil broth. Our Super Soil-based method can be used to rapidly generate large quantities of chlamydospores for infecting plants and for studying factors affecting the survival of the Fusarium wilt pathogen in soil.
A soil broth made from the commercial potting mix Super Soil induced rapid production of chlamydospores in many isolates of Fusarium oxysporum. Eight of 12 isolates of F. oxysporum f. sp. vasinfectum produced chlamydospores within five days when grown in Super Soil broth. The chlamydospore-producing isolates included four known races and four genotypes of F. oxysporum f. sp. vasinfectum. One isolate of race 4 consistently produced greater than 10 million chlamydospores per 50 ml of inoculated Super Soil broth. The Super Soil broth also induced rapid chlamydospore production in three other formae speciales of F. oxysporum: f. sp. lycopersici, f. sp. lactucae, and f. sp. melonis. No change in chlamydospore production was observed when variations of the Super Soil broth (no glucose added, no light during incubation, and 60-min autoclave times) were tested on six isolates of F. oxysporum f. sp. vasinfectum. Lab-generated chlamydospores may be useful for pathogenicity assays and studies of pathogen survival in soil.