COMPARISON OF VIRUS-FREE AND VIRUS-INFECTED CLONES OF TWO PEAR CULTIVARS

Between 1975 and 1984 various virus-free clones of the pear cultivars Conference and Doyenné du Comice on virus-free Quince A rootstock were compared at two locations.
Some of the clones were infected with a complex of five viruses shortly after budding.
The viruses involved were vein yellows, ring pattern mosaic, quince stunt, quince sooty ring spot, and rubbery wood.
In both cultivars clones showed differences in growth vigour, productivity both per tree and per unit of tree volume, fruit size, and fruit-skin russeting.
Flowering intensity was not apparently affected.
Russeted clones were less productive than smooth-skinned clones.
Since for Conference the market demands russeted fruits, preference must be given to clones that are sub-optimal with respect to cropping potential.
This is not the case for Doyenné du Comice, because here smooth fruits are preferred.

The virus complex reduced growth, increased variability in growth, caused leaf chlorosis in Conference, and reduced productivity per tree but not per m³ tree volume.
Often, productivity per m³ tree volume was enhanced, which explains part of the observed decrease in fruit size.
Flowering was not affected by the viruses.

There were some discrepancies in the results obtained in the two orchards, indicating that it might be useful to carry out clonal selection similtaneously in various locations.
The results are discussed, and it is concluded that both clonal selection and virus elimination are necessary to provide the pear industry with optimal starting material.

Workshop on Clonal Selection in Tree Fruit

S.J. Wertheim, H.J. van Oosten

https://doi.org/10.17660/ActaHortic.1986.180.6