Variation in production of phomodiol and phomopsolide B byPhomopsisspp.

Abstract

Naming Phomopsis spp. based on the identity of their host plant has been a common prac- tice. Taking this into account, we compared produc- tion of two secondary metabolites by Phomopsis iso- lates among isolates from a single plant genus and isolates from various plant genera. Phomopsis spp. growing endophytically in willow twigs were isolated from seventeen of the seventy-three trees of Salix species sampled at seven sites in England and New Jersey, USA. No correlations appeared to exist be- tween presence of the fungus and host plant species or geographical location. Fifty-two of these Phom- opsis isolates from willows, as well as eight from oth- er nonwillow plants, were fermented in both malt and millet media to assay for the production of the Phomopsis secondary metabolites phomopsolide B and phomodiol. Phomopsolide B was almost univer- sally produced by the isolates from willows, while it was produced by only one of the nonwillow isolates. Phomodiol production varied among all isolates. Isolates obtained from the same tree also varied in production of these metabolites. A high degree of flask-to-flask variability in production of these me- tabolites by a single isolate was found, which sug- gested that the presence or absence of a metabolite was more meaningful than the absolute amount pro- duced.