Effect of Rootstock, Scion Variety and Virus Complement on Fruit Production and Growth of Young Apple Trees

SummaryFruit production for the age interval 5 to 10 years and total growth of trees of cvs. Red Jonathan and Granny Smith propagated on Sturmer Pippin seedlings and on Malling-Merton 104 clonal stocks were studied in the presence or absence of apple mosaic strains of Prunus necrotic ringspot virus from mildly and severely diseased sources.Production and growth of Red Jonathan on both stocks were reduced by mosaic. No reduction occurred in Granny Smith when propagated on MM. 104. A consistent interaction occurred between infection source and variety. Relative fruitfulness of trees, when expressed as total crop per unit cross section of trunk, was significantly reduced for Red Jonathan but not for Granny Smith by mosaic from the severely diseased source.