New Zealand Journal of Crop and Horticultural Science abstracts
Past and present status of virus and phytoplasma diseases
in apple rootstocks in New Zealand
G. A. WOOD
The Horticulture and Food Research
Institute of New Zealand
Mt Albert Research Centre
Private Bag 92 169
Auckland, New Zealand
Abstract The high incidence of virus and phytoplasma diseases
in older apple (Malus domestica Borkh.) trees in New Zealand can be
traced in part to infection in the `Northern Spy' clonal rootstock which was
used extensively in the early part of this century to combat woolly apple aphid
infestation, and in the `Malling' series of clonal rootstocks which were
imported in 1930 for controlling the size of apple trees. The "latent virus
infections"--stem pitting, stem grooving, chlorotic leaf spot, and scaly bark
were commonly present in these rootstocks, as was apple mosaic virus. The
phytoplasma disease rubbery wood occurred only in `Malling 12'. Presence of
apple mosaic virus and rubbery wood phytoplasma in the rootstocks may explain
the unusually high incidence of these two diseases in New Zealand apple trees
in comparison to other apple growing countries. Most of the apple rootstocks
imported since 1936, which include the now widely used `Merton 793' and
`Malling-Merton 106', were free from infection when imported. In tests for
virus and phytoplasma diseases in rootstocks grown in 12 commercial nurseries
from 1987 to 1995, most were free from infection. Stem pitting, stem grooving,
chlorotic leaf spot, and scaly bark viruses were found in a few of the samples
tested, but none were infected with either apple mosaic virus or rubbery wood
phytoplasma.
Keywords apple rootstocks; virus disease; phytoplasma
disease; disease testing
New Zealand Journal of Crop and Horticultural Science, 1996, Vol. 24:
133-141
0114-0671/96/2402-0133 $2.50/0 (c) The Royal Society of New Zealand
1996
PDF file of entire paper: medium quality (716K); (scanned from paper original: notes about this process)
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