Four Diaporthe species associated with grapevine nursery plants and commercial vineyards in Uruguay

Diaporthe species cause Diaporthe dieback (DD) in many grape‐growing countries causing general vine decline, shoot dieback and dead spurs, with perennial cankers and internal trunk necrosis. These pathogens are also the causal agents of Phomopsis cane and leaf spot, a common foliar disease affecting grapevine around the world. In this study, we specifically investigated DD affecting nursery vines and commercial vineyards in Uruguay. A collection of 59 Diaporthe isolates obtained from symptomatic and asymptomatic wood samples of commercial grapevines (nine cultivars) and nursery vines (including cuttings of four scion cultivars and two rootstocks, and six scion–rootstock combinations of grafted plants), was characterized based on DNA phylogenetic analysis, phenotypical characteristics and pathogenicity tests. Diaporthe ampelina was the most frequent species (86%), followed by D. foeniculina (9%), D. eres (3%) and D. terebinthifolii (2%). All species were isolated from nursery material, but D. ampelina was the only one found in field vines. The pathogenicity of all species was confirmed, with D. ampelina being the most virulent, causing the longest necrotic lesions on both green shoots and lignified canes. Further studies are needed to comprehend the epidemiology of DD and to better understand its relationship with Phomopsis cane and leaf spot in order to design a management programme to prevent the disease development. Diaporthe species were identified colonizing the internal wood of field vines and nursery plants in Uruguay, with D. ampelina standing out as the most prevalent and aggressive species in pathogenicity tests.