Pathogenicity and molecular identification of Botryosphaeria spp. on vitis vinifera in the Hunter Valley

Species of the fungus Botryosphaeria are responsible for
cankers in the wood and bunch rots of grapevines. Pathogenicity
tests have been conducted on grapevine wood for several species,
but it is unknown which of these infect bunches. Botryosphaeria
spp. have been isolated from bunches in Australian vineyards, but
again little is known about the infection pathway into bunches.
This project aims to identify Botryosphaeria spp. isolated from
grapevines at different phenological stages (dormant buds, flowers, pea-sized berries, berries at veraison and berries at harvest)
and from the wood. Samples will be collected over 3 seasons from
Vitis vinifera cv. Chardonnay and Shiraz from two vineyards in the
Lower Hunter Valley in south-eastern Australia. Pathogenicity
tests will be conducted on berries using the species isolated from
the survey. Species variation within a plant will be analysed and
compared to the species found in diseased wood of the same
plant. To date, Botryosphaeria spp. have been isolated from 6%
(3% from Chardonnay and 3% from Shiraz) of bud samples in
one vineyard, and 17% (12% from Chardonnay and 5% from
Shiraz) in a second vineyard. Botryosphaeria spp. have also been
isolated from approximately 50% of the wood samples collected
from these vineyards. The results from this study will contribute
to understanding the epidemiology of Botryosphaeria bunch rot
and will lead to better management strategies for this disease.