First Report of Phaeomoniella chlamydospora on Vitis vinifera and French American Hybrids in Chile

Biocontrol Potential of Grapevine Endophytic and Rhizospheric Fungi Against Trunk Pathogens

Grapevine Trunk Diseases (GTDs) are a major challenge to the grape industry worldwide. GTDs are responsible for considerable loss of quality, production, and vineyard longevity. Seventy-five percent of Chilean vineyards are estimated to be affected by GTDs. GTDs are complex diseases caused by several fungi species, including members of the Botryosphaeriaceae family and Phaeomoniella chlamydospora, considered some of the most important causal agents for these diseases in Chile. In this study, we isolated 169 endophytic and 209 rhizospheric fungi from grapevines grown under organic and conventional farming in Chile. Multiple isolates of Chaetomium sp., Cladosporium sp., Clonostachys rosea, Epicoccum nigrum, Purpureocillium lilacinum, and Trichoderma sp. were evaluated for their potential of biocontrol activity against Diplodia seriata, Neofusicoccum parvum, and Pa. chlamydospora. Tests of antagonism were carried out using two dual-culture-plate methods with multiple media types, including agar containing grapevine wood extract to simulate in planta nutrient conditions. Significant pathogen growth inhibition was observed by all isolates tested. Clonostachys rosea showed 98.2% inhibition of all pathogens in the presence of grapevine wood extract. We observed 100% pathogen growth inhibition when autoclaved lignified grapevine shoots were pre-inoculated with either C. rosea strains or Trichoderma sp. Overall, these results show that C. rosea strains isolated from grapevines are promising biocontrol agents against GTDs.

Infection Caused by Phaeomoniella chlamydospora Associated with Esca-like Symptoms in Grapevine in Chile

Trunk diseases such as esca have been recognized as an economically important problem of grapevine worldwide. A study was conducted to characterize the distribution of Phaeomoniella chlamydospora in Chile. A field survey of young and mature grapevines from 67 vineyards located along a 1,315-km north-south axis demonstrated that P. chlamydospora was present in 94.9% of the grapevine samples showing the black-wood streaking symptom (BWS) but not the characteristic foliar symptoms of esca. Phylogenetic analysis of the ribosomal DNA internal transcribed spacer (ITS) combined with β-tubulin (BT) genes grouped Chilean isolates together with reference isolates from South Africa and the United States, whereas Spanish isolates were clustered separately. Chilean isolates differed by only 2 to 3 bp for BT and ITS, respectively. Conidia germinated at 5 to 35°C, with an optimal temperature of 25 to 30°C. Isolates were pathogenic, and Koch's postulates were fulfilled in separate sets of inoculations of axenic plantlets, cuttings, 2-year-old plants, spurs, and shoots of V. vinifera. This study showed that P. chlamydospora was associated consistently with BWS and no other apparent symptom in young and mature grapevines, including nursery plants, in Chile. Inoculum was absent from the soil, grapevine pruning debris, sap samples, and herbaceous weeds, which is in contrast to past studies. At this time, Vitis spp. are the only known hosts of P. chlamydospora in Chile.