ASSOCIATION OF APPLE STEM GROOVING VIRUS WITH A DECLINE OF PACKHAM’S TRIUMPH PEAR ON SEEDLING ROOTSTOCK

A progressive decline of Packham’s Triumph pear grown on seedling rootstock is widespread in pear orchards of the Western Cape Province of South Africa.
Initial symptoms are reduced terminal growth and die-back of feeder roots.
These are usually observed on trees more than seven years old.
Trees in advanced decline show scion overgrowth of the seedling rootstock.
Removal of bark at the bud-union of affected trees reveals various degrees of grooving on the trunk of the seedling rootstock.
Indexing of affected orchard trees on Pyronia veitchii and Nicotian glutinosa confirmed the common presence of apple stem grooving (ASG) virus.
The development of a slight to severe decline of 42% of William’s Bon Chretien pear seedlings budded with material from affected orchard trees suggested an association of ASG virus with the random decline of Packham’s Triumph on a virus-sensitive seedling rootstock.
The importance of ASG virus in a similar but less conspicuous decline of other pear cultivars are at present under investigation.

XII International Symposium on Fruit Tree Virus Diseases

Van Z. Siebert, D.J. Engelbrecht

https://doi.org/10.17660/ActaHortic.1983.130.5