Evaluating Grapevine Cultivars for Resistance to Anthracnose Based on Lesion Number and Length

Anthracnose is one of the most detrimental diseases of grapevines in humid regions. To lessen the risk of crop damage and to reduce fungicide application, resistant cultivars are needed. The resistance of grapevines to anthracnose caused by Elsinoe ampelina (de Bary) Shear was evaluated in two ways: the resistance against ingress was evaluated using the number of lesions and the resistance against colonization was evaluated using the lesion length. First, both forms of resistance in 13 cultivars were evaluated in a detached-leaf assay for three years using greenhouse-grown cuttings. Both lesion number and lesion length revealed a genetic component of the resistance, with greater phenotypic variation among interspecific hybrid cultivars than among Vitis vinifera cultivars. The detached-leaf assay revealed significant differences in lesion length among V. vinifera accessions; Exotic and Perlette showed moderate resistance. Lesion diameters were measured in a fungicide-free vineyard to evaluate the resistance of six cultivars, and significant differences were found among the cultivars. The lesion shape in susceptible cultivars was almost circular, whereas the shape in resistant cultivars was usually irregular. Results showed that evaluations based on the lesion number and length can reliably predict resistance to anthracnose without the need for large field trials and that some V. vinifera cultivars exhibited moderate resistance to this disease.