EFFECT OF VIRUS INFECTION ON THE PERFORMANCE OF McINTOSH APPLE TREES ON SELECTED SEEDLING AND CLONAL ROOTSTOCKS

Abstract

A field experiment conducted over 12 yr showed virus inoculation with Spy decline, chlorotic leaf spot, stem pitting, rubbery wood and apple stem grooving viruses generally reduced tree size and yield of two strains of the McIntosh apple cultivar. Virus-inoculated trees flowered and fruited slightly ahead of uninoculated trees. Trees on Ottawa Hybrid (OH)-1, OH-5, Ottawa (0)-5, 0-7, 0-11 and Malus robusta Rehd. 5 rootstocks were the most sensitive to virus infection, while trees on OH-3, OH-4, OH-6 and O-3 were relatively tolerant to virus infection. Virus infection did not reduce yield efficiency (kilograms of fruit per unit of trunk cross sectional area). Fruit from trees inoculated with virus was generally smaller in size but had more red color than fruit from uninoculated trees.Key words: Malus domestica, Ottawa rootstocks, yield, tree size, fruit quality, virus sensitivity