Sensitivity of Populus tremuloides to toxic metabolites of Hypoxylon mammatum and susceptibility to H. mammatum infection

Abstract

The response of 17 aspen tissue culture clones to bioassays with metabolites of Hypoxylon mammatum and in vitro inoculation with H. mammatum ascospores was determined. Although statistically significant variation among aspen clones was observed in response to both bioassays, response of the clones to the assays was not related (r = 0.361). This suggests that H. mammatum metabolites are not essential for the infection of tissue cultured aspen. Forty plantation-grown aspen differing in response to natural H. mammatum infection were also tested for sensitivity to metabolites of H. mammatum. Large differences in the sensitivity of the clones to the metabolites were observed, but these differences were not related to the disease condition of the clones. The toxic metabolites isolated from H. mammatum had no effect on the growth of fungi isolated from healthy aspen stems. Overall, these results suggest that the sensitivity of aspen to H. mammatum toxic metabolites is only one of the several factors influencing susceptibility. Key words: Populus tremuloides, Hypoxylon mammatum, phytotoxin.