Differentiation of Fusarium oxysporum isolates from Phoenix canariensis (Canary Island Date Palm) by vegetative compatibility grouping and molecular analysis

Abstract

Fusarium wilt of Phoenix canariensis (Canary Island Date Palm) is caused by Fusarium oxysporum f. sp. canariensis (Foc). The disease occurs worldwide, including Australia where hundreds of palms have been killed. Isolates of Foc were collected from fronds of diseased palms at sites around Sydney and different parts (non-frond) of individual palms within a site. Three techniques were used to assess diversity of these isolates; vegetative compatibility groupings, PCR testing for a sequence previously shown to be associated with pathogenicity and DNA fingerprinting using ERIC primers. The combined methods divided the isolates into one major and four minor groups, with two of the minor groups showing some bridging characters. ERIC PCR showed these groups to be different from six overseas isolates of Foc, five of which belonged to VCG 0240. A minority of isolates did not fall into any group and are presumed saprophytes. Some discrepancies in the expected correlation between the techniques occurred for the non-frond isolates; this has implications for appropriate tissue selection for disease diagnosis. The number of groups and the differences between them indicate a degree of diversity comparatively higher than that shown in other studies for this forma specialis and may have important consequences for disease management.