Species of Phomopsis and a Libertella sp occurring on grapevines with specific reference to South Africa: morphological, cultural, molecular and pathological characterization

In order to clarify the taxonomy of species of Phomopsis associated with gr apevines, 61 isolates were obtained from 58 different vineyards in the grap evine growing areas of the Western Cape province of South Africa. Species d elimitation was primarily based on alpha conidium and conidiophore morpholo gy, cultural characteristics, pathogenicity to Vitis vinifera, and the abil ity to form the teleomorph in vitro. The identity of each taxon was confirm ed by means of phylogenetic analyses of the nuclear ribosomal DNA internal transcribed spacers (5.8S, ITS1 and ITS2) and the 5' end partial sequence o f the mitochondrial small subunit (mtSSU). We also re-examined the four tax a that previously had been associated with grapevines in Australia. Three o f the latter taxa, and a Phomopsis species commonly associated with shoot b light of peaches in the USA, P. amygdali, were identified among the South A frican isolates. Phomopsis amygdali was isolated once only and appeared to be of lesser importance in this disease complex. Furthermore, Diaporthe per juncta and Phomopsis sp. 1 were also rarely encountered and proved to be no npathogenic, indicating their nonfunctional role in Phomopsis cane and leaf spot disease. Phomopsis viticola was common and widely distributed through out diseased vineyards. This taxon was associated with the typical cane and leaf spot disease symptoms and proved to be highly virulent. Morphological ly collections designated in previous studies as taxon 2 corresponded best with P. viticola, which was also neotypified in this study. Examination of the Australian culture designated as taxon 4 revealed it to be a species of Libertella, thus excluding it from the P. viticola complex. An Italian iso late was found to represent a species of Phomopsis not previously known fro m grapevines, and this was subsequently designated as Phomopsis sp. 2. A ke y to taxa of Phomopsis from grapevine is also provided.