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ILYONECTRIA IN GRAPEVINE PROPAGATION NURSERY SOIL IS A CAUSE OF
YOUNG VINE DECLINE IN THE RIVERINA
M.A. Whitelaw-Weckert A , L. Rahman A
A
National Wine and Grape Industry Centre, NSW Department of Primary Industries, Charles Sturt University, Wagga Wagga, NSW,
Email: melanie.weckert@dpi.nsw.gov.au
ABSTRACT. The unexplained deaths of newly planted grapevines is of great economic importance to Riverina wine-grape
growers. Vines from the same propagation nursery batches that do not die immediately are often developmentally retarded
and usually die within a few years. Characteristic symptoms include very short shoots, low yields and severely stunted roots
with black sunken necrotic root lesions. ‘Black goo’ symptoms are absent and the Petri disease fungi not consistently
isolated, although members of Botryosphaeriacea are often isolated from below the graft union, both in trunks and roots. In
an attempt to determine the cause of young vine decline in the Riverina, NSW, we surveyed 20 affected vineyards. Fungi
were isolated from the root system and trunks of six uprooted grafted Chardonnay grapevines from each vineyard. Isolates of
two pathogenic Ilyonectria species (cause of ‘black foot’) were isolated from the rootstocks of every diseased grapevine
examined. When plants from a propagation nursery supplying the diseased vineyards were sampled, every rootstock stem
examined showed disease symptoms. In addition, nursery soil and roots were consistently infected with Ilyonectria. Root
inoculation of potted Chardonnay with Ilyonectria isolates from the diseased vineyards resulted in symptoms typical of
black-foot disease. We conclude that a major initial cause of young vine decline in the Riverina is infection by Ilyonectria
spp. from nursery soil.
INTRODUCTION
Wine grape-growers in Australia’s Riverina wine region
have reported the deaths of many newly planted grapevines.
Characteristic symptoms included very short shoots, low
yields, severely stunted roots with few feeder roots, black
sunken necrotic root lesions and premature death. The
objective of this study was to elucidate the pathogens
responsible for young vine decline in the Riverina. As the
Riverina grapevine roots were severely stunted, we
expanded on the earlier Australian investigation (1) by
including grapevine roots as well as rootstock trunks, scion
trunks and cordons.
MATERIALS AND METHODS
Vineyard and propagation nursery isolations We
conducted an investigation into the incidence of wood and
root fungal pathogens from one year-old vines in a
propagation nursery and six whole vines from each of 20
Riverina vineyards with young vine decline. Roots and
trunk pieces were surface sterilised (3 min 1% chlorine and
3 washes SDW) and plated on Dichloran Rose Bengal
Chloramphenicol agar. They were also moist incubated for
extended periods.
Bait plants Chardonnay bait plants (four replicates) were
grown for one year in soil from four sites: (A) adjacent to
newly planted diseased vines in vineyard; (B) a ‘diseased’
field site in the nursery supplying the vineyard; (C) soil from
site B, sterilised by autoclaving and (D) a healthy field site
within the same nursery.
Rapid pathogenicity assay on Chardonnay grapevine
seedlings Grapevine seeds (Chardonnay) were surface
sterilised in 0.5M H 2 O 2 for 24h. The seeds were then
washed with SDW three times and soaked for 5 min in 2%
hydrogen cyanamide (H 3 NCN, Sigma) to break dormancy.
The seeds were planted in sterile potting mix until the
seedlings were 4 cm high. They were then dipped for 30
min into a suspension of conidia and mycelium (1 x 10 5
spores mL - 1) of Ilyonectria macrodidyma (DAR81461)
isolated from a rootstock trunk from one of the surveyed
vineyards. Control plants were dipped in water. The
seedlings were planted in sterile potting mix in 1.2 L pots
arranged in randomised complete blocks in a glasshouse
maintained at 15–25 ◦ C and watered to field capacity. The
roots for both the above bait plant and seedling pot
experiments were scored for root health and roots and stems
were surface sterilised and incubated first on DRBC and
then PDA as above. Root and shoot dry weights (50°C until
constant weight) were determined. Data were subjected to
analysis of variance (anova) test and least significant
differences were calculated at P< 0·05 using Genstat for
Windows, 8th edition.
RESULTS and DISCUSSION
I. macrodidyma or I. liriodendri were isolated from 100% of
all selected diseased grapevines in the 20 vineyards
investigated. In the propagation nursery, every rootstock
stem plus the soil and roots investigated were infected with
Ilyonectria. Petri disease fungi were isolated from 22% of
vineyard vines. Botryosphaeriacea fungi were isolated from
89% of rootstock trunks and our investigations showed that
these originated in rootstock mother vine cuttings (data not
shown). No pathogens were isolated from the Chardonnay
bait plants in (A) vineyard soil, (C) sterilised diseased
nursery soil, or (D) healthy nursery soil, but I. macrodidyma
was isolated from the nursery soil from the diseased nursery
site (B) and the roots were significantly stunted (Table 1).
The pathogenicity assay on Chardonnay seedlings showed
that, within 5 weeks after inoculation, I. macrodidyma had
caused severe root disease symptoms (data not shown).
Table 1. Pathogens from Chardonnay bait plant roots.
Source of soil Pathogens
isolated
Root dw
(g)
(A) Vineyard 0 7.1 a,b
(B) Nursery soil from I.
4.0 b
‘diseased’site macrodidyma
(C) Sterilised nursery 0 9.7 a
soil from ‘diseased’
site
(D) Nursery soil from 0 12.5 a
second (‘healthy’) site
P - 0.033
l.s.d. - 5.4
Values within a column followed by the same letter are not significantly
different based on l.s.d. (P=0.05).
Conclusion. Two Ilyonectria species, cause of blackfoot in
Australia (2) were consistently involved in young vine
decline in the Riverina. The high Ilyonectria inoculum level
in the nursery field soil is of serious concern for Australian
viticulture.
ACKNOWLEDGEMENTS
The research was supported by the GWRDC. We thank
Lynne Appleby for technical support.
REFERENCES
1. Edwards, J.and Pascoe I.G ( 2004) Australasian Plant
Pathology 33, 273-279.
2. 2. Whitelaw-Weckert, M.A; Nair N.G.; Lamont, R; Alonso
M; Priest M.J; Huang, R. (2007). Australasian Plant
Pathology 36, 403-406.
7th Australasian Soilborne Diseases Symposium 41