Yield and Berry Composition of Five Vitis Cultivars as Affected by Rupestris Stem Pitting Virus

Abstract

Rooted cuttings of Kerner (Vitis vinifera), Michurinetz (V. amurensis X), and Okanagan Riesling (V. labrus- cana X), either virus-free or infected with Rupestris stem pitting virus (RSPV), were planted in 1987 in a randomized block experiment at Summerland, British Columbia (arid continental climate). Also, virus-free and RSPV-infected plants Madeleine Sylvaner, and Ortega (both V. vinifera) were planted in a completely randomized experiment at Saanichton Plant Quarantine Station, Sidney, BC (cool maritime climate). Yield components were not affected at the Summerland site, but weight of cane prunings were reduced in RSPV- infected Michurinetz vines in 1995-96. RSPV also lowered yield and clusters per vine of both cultivars in 1994 at Sidney, along with Ortega weight of cane prunings (1993 and 1994) and berry weight (1994). Berry titratable acidity (TA) at harvest was reduced at both sites in RSPV-infected vines, and pH was concomitantly increased. TA was consistently lower and the pH was always higher in the RSPV berries during veraison to harvest at Summerland. No apparent negative impact of RSPV was observed except delayed soluble solids (°Brix) accumulation in RSPV-infected Kerner and Okanagan Riesling vines at Summerland in 1991, and lower °Brix in Ortega RSPV berries at Sidney in 1993. In some seasons, fruit composition differences between virus-free and RSPV vines disappeared close to commercial maturity, but lower TA and higher pH persisted until harvest at the Summerland site in 1993. RSPV-infected vines at Sidney exhibited slightly delayed budburst in 1988-91 and 1994, but not 1993. These results suggest that RSPV has no major impact on grapevine growth and yield, and may advance fruit maturity in terms of TA and pH.