Endophytic fungi associated with shoots and leaves of Vitis vinifera, with specific reference to the Phomopsis viticola complex
Phomopsis cane and leaf spot caused by Phomopsis viticola is an economically important disease in many of the vine-growing areas of the world. The aims of this study were to investigate whether P. viticola grows endophytically in various vine tissues, and to monitor its distribution over the growing season. Asymptomatic shoots were collected at eight different growth stages. Nodes, internodes, leaf petioles, leaves, tendrils and bunch rachides were surface sterilised, cut into smaller pieces and plated out on potato dextrose agar. After the fungal endophytes were identified, the relative importance (RI) values were calculated and a correspondence analysis performed on the data of taxa with RI larger than 5%. Of the 46 different fungal taxa found, 20 were present at relative importance values of more than 1%. An analysis of the relative importance of the different species showed that the most frequently isolated fungi were members of the Alternaria alternata complex (40%) and Sphaeropsis sp. (27%). The Phomopsis viticola complex had a relative importance of 9% and accounted for 3% of the isolations. P. viticola was mainly isolated from the nodes and internodes, the plant parts in which P. viticola usually causes disease symptoms. Two different Phomopsis spp. were isolated, with 94% of the isolates representing P. viticola taxon 2, and the rest taxon 1. Isolations made from diseased vine material during the last two years revealed taxon 2 to be dominant in vineyards in the Western Cape. Inoculations into healthy, young vine tissue also showed taxon 2 to be a primary pathogen, further suggesting that it is probably a latent pathogen rather than an endophyte. In contrast, taxon 1 appears to be a true endophyte, and does not seem to be an important pathogen on vines.