Vegetative Compatibility Groups in Fusarium proliferatum from Asparagus in Australia

Abstract

Seventy-seven isolates of Fusarium proliferatum from seven asparagus growing regions in Australia were placed into vegetative compatibility groups (VCGs) using heterokaryon tests with nitrate nonutilizing mutants. Isolates also were tested for pathogenicity on asparagus seedlings. Ten VCGs were identified which comprised 56 (75%) of the total isolates. All isolates in these 10 VCGs except one were ranked as pathogenic on asparagus seedlings. The largest VCG (VCG US5) contained 23 isolates (30% of total) and was recovered from fields around Mildura, Victoria, Cowra, New South Wales, and Perth, Western Australia. VCG US5 was previously found to be the largest VCG in the United States. Two VCGs, previously identified in the US, were found in Australia. The remaining 19 isolates were not vegetatively compatible with any other isolate in our tests, and at present, remain single members of a VCG. Four of the 19 isolates were ranked as nonpathogenic. These findings show that a large percentage of the pathogenic isolates of F. proliferatum sampled from asparagus in Australia belong to VCGs common on asparagus in the USA. The pathogen is probably disseminated between countries on seeds and crowns.