The influence of rainfall on the mycobiota isolated from grapevine pruning wounds.

Grapevine trunk diseases cause substantial economic loss worldwide. Grapevines are susceptible to infection by the causal agents when pruning during dormancy coincides with rainfall. The ascospores of Eutypa lata, the causal agent of the trunk disease Eutypa dieback, are released by fruiting bodies following rainfall and infect fresh wounds in woody tissue. Wound-colonising microbes have the potential to compete with the pathogen but the effect on such microbes of exposure of wounds on grapevines to rainfall has not been investigated. The presence of microbes in grapevine pruning wounds, both exposed to and sheltered from rainfall, was investigated at weekly intervals for one month following pruning. Surface disinfected tissue was cultured and the predominant microbes identified by morphology and by Sanger sequencing. Epicoccum nigrum, Aureobasidium pullulans, Alternaria and Cladosporium spp. were the predominant fungi, E. lata was not isolated and bacteria were isolated only rarely. The number of microbes found in rainfall-exposed wounds was greater than in those protected from rainfall and, of the above-mentioned, Epicoccum nigrum was predominant. Three of these species competed for space with E. lata when co-cultured in vitro. [ABSTRACT FROM AUTHOR]