Differential reactivity of grapevine cultivars to "Bois Noir" infections in Sardinia

• Published in: Journal of plant pathology Vol. 86; no. 4; p. 320
• Main Authors: Garau, R, Tolu, G, Prota, V A, Sechi, A
• Format: Journal Article
• Language: English
• Published: 01-12-2004
• Subjects: Aster yellows; Flavescence doree; Phytoplasma; Italy, Sardegna
• ISSN: 1125-4653

Differences in symptomatological reactions of cvs Vermentino, Vernaccia di Oristano, Cannonao and Chardonnay to "Bois Noir" infections were observed in the course of field surveys carried out since 1999 in Sardinia. 'Vermentino' plants were monitored for 5 years, 'Vernaccia' for 3 and both 'Cannonao' and 'Chardonnay' for 2 years. Surveys for symptoms displayed over time by some 200 plants of each cultivar in different periods of the year, showed that the total incidence of symptomatic vines was 14% in 'Vermentino', 83% in 'Vernaccia di Oristano', 61% in 'Cannonao' and 17% in 'Chardonnay'. Symptoms were not univocal as they varied according the hosts. Thus, 'Chardonnay' exhibited typical symptoms on the leaves, bunches, and shoots from July onwards, with the highest incidence in September. 'Vernaccia di Oristano' and 'Vermentino' had an intermediate susceptibility, symptoms on the leaves were delayed, whereas irregular lignification of shoots and withering of bunches were erratic. 'Cannonao' showed early rolling of the top leaves associated with discolorations of the leaf margins, and no significant damage to bunches. Remission of symptoms was observed in 62% of diseased 'Vermentino' plants. New possible infections were found in the third year in 19% 'Vernaccia' and 4% 'Vermentino' vines. Monthly molecular assays by nested PCR followed by RFLP analysis of amplicons with restriction endonuclease MseI, allowed the identification for each cultivar of the best time for the detection of phytoplasmas of subgroup 16SrXII-A. Thus, 'Vermentino' was positive in June and September, 'Vernaccia di Oristano' only in summer, 'Cannonao' in June, and 'Chardonnay' from June to September. Phytoplasmas of groups 16SrV (Flavescence doree) and 16SrI (Aster yellows) were not found.