EFFECTS OF VIRUS AND VIRUS-LIKE INFECTIONS ON GROWTH, YIELD, AND FRUIT-QUALITY OF ALBANA AND TREBBIANO-ROMAGNOLO GRAPEVINES

The effects of some grapevine virus and virus-like diseases on the per formance of Vitis vinifera cv. Albana and cv. Trebbiano Romagnolo, wer e studied in a replicated field trial in the Emilia Romagna region (no rth Italy). Healthy vines were inoculated by grafting bud material fro m different source vines with single and multiple infections, Plant gr owth and yield were measured over a seven-year period, 1987 to 1993. F ruit maturity indices (degrees Brix, titratable acidity and pH) were m easured over a six-year period, 1988 to 1993. The assessment revealed a marked influence on yield and growth of three inoculum sources (A, B , and Fl which induced visible symptoms on vines, Sources A and B decr eased the cumulative fruit yield by 14.2% and 72.9% (p < 0.05) in cv. Albana and 80.4% (p < 0.05) and 46.6% in cv. Trebbiano Romagnolo. Annu al cumulative growth was reduced by 17.2% and 67.8% (p < 0.05) in cv. Albana and by 78.1% (p < 0.05) and 39.1% in cv. Trebbiano Romagnolo. S ource F, only inoculated in the latter, induced yield and growth losse s of 21.2% and 23.1%. On the contrary, when four sources (C, D, E, and G) of latent and semi-latent infectious diseases were graft-transmitt ed, no significant effects were observed, In general, no consistent di fferences in the fruit maturity indices were obtained in any of the in oculated cultivars, although, cv. Albana vines, infected with source B , showed higher sugar concentrations (significant in 5 out of 6 harves ts), Moreover, the six-year weighted means for titratable acidity and pH were significantly lower (p < 0.05) in vines inoculated with source A.