N. G Nair

Evidence of early flower infection in olives (Olea europaea) by Colletotrichum acutatum and C. gloeosporioides causing anthracnose disease

New evidence is provided for early asymptomatic infection of flowers of olive varieties Barnea and Manzanillo byColletotrichum acutatum andC. gloeosporioides. Asymptomatic infection of olive flowers by these species ofColletotrichum and the likely quiescent behaviour of the pathogens resulting in symptomatic disease expression of mature fruits has not been recorded anywhere previously.

Root infection of Vitis vinifera by Cylindrocarpon liriodendri in Australia

Cylindrocarpon liriodendri was isolated from the roots of diseased own-rooted grapevines (Vitis vinifera cv. Pinot Noir) from the Hunter Valley, New South Wales, Australia. Sequencing of the β-tubulin 2 gene established the identity of the pathogen as C. liriodendri. Soil/root inoculation of potted V. vinifera cv. Chardonnay vines resulted in symptoms typical of black-foot disease. This study has established the pathogenicity of an Australian isolate of C. liriodendri on V. vinifera.

First report of Colletotrichum acutatum and C. gloeosporioides causing leaf spots of olives (Olea europaea) in Australia

We report the occurrence ofColletotrichum acutatum andC. gloeosporioides on leaves of olives (Olea europaea) for the first time in Australia.

First report of anilinopyrimidine-resistant phenotypes in Botrytis cinerea on grapevines in Australia

Anilinopyrimidine-resistant phenotypes of Botrytis cinerea are recorded for the first time in Australian vineyards. The frequency of resistance among the 910 isolates obtained during 1997/98, 1999/2000 and 2000/01 was 0%, 12% and 4%, respectively. There were two resistant phenotypes and these were designated as low resistant (EC50=1.5 mg/L) and resistant (EC50=2.5 mg/L). Both the resistant phenotypes were found to possess multiple resistances to benomyl (benzimidazole) and iprodione (dicarboximide). It is considered that the frequency of anilinopyrimidine resistance observed currently in Australian vineyards does not pose any immediate risk in the use of pyrimethanil for management of Botrytis bunch rot.

Species of Pestalotiopsis and related genera occurring on grapevines in Australia

Descriptions of several appendage-bearing coelomycetes such as Pestalotiopsis and related genera occurring on grapevines in Australia are given. Species isolated included Pestalotiopsis uvicola, P. menezesiana, Seirnatosporium hysterioides, Truncatella angustata, and Sporocadus rhododendri. Infection studies showed that berries of grapevines were infected by P. uvicola more readily at later stages of berry development than at the earlier stages.

Germination of β conidia of Phomopsis viticola

Germination of β conidia of Phomopsis viticola was recorded in potato-dextrose liquid medium but not in sterile distilled water. Maximum germination of β conidia in vitro occurred within 144 h reaching a plateau around 60–80 h at 26°C, whereas α conidia germinated within 28 h at 30°C. Preliminary bioassays indicated that the β conidia are potentially capable of symptomless infection of grapevine leaves. However, further studies are required to confirm this.

The use of fluorochromes to determine the effect of chlorine dioxide on survival of Plasmopara viticola on grapevine

A technique using fluorochromes was developed to quantify the survival of Plasmopara viticola on the leaves of grapevine cv. Chardonnay following application of chlorine dioxide (ClO2). The staining combination of 5,6 carboxyfluorescein diacetate and propidium iodide produced intense green fluorescence of live conidia and red fluorescence of dead conidia of the fungal pathogen under blue excitation. The number of live conidia on the leaves emitting green fluorescence decreased significantly with increase in the concentration of ClO2. The percentage of dead conidia on leaves treated with 25 or 50 ppm of ClO2 were 38 and 99, respectively. No conidia survived on leaves treated with 100 ppm of ClO2. The bioassay can be applied to studies on screening fungicides for disease control. The advantages of the fluorochrome bioassay used in this study are that it is faster than measuring germination of conidia, and that it gives a quantitative estimate of survival of the pathogen.

Survival of Phomopsis viticola in grapevine cuttings after hot water treatment

Hot water treatment (HWT) at 50°C for 30 min reduced the survival of Phomopsis viticola in infected grapevine cuttings from 75.6% to 0.7%. Submerging cuttings in chlorinated water did not affect survival of the pathogen. Survival of P. viticola in cuttings of Sultana and Waltham Cross (cultivars of Vitis vinifera) after hot water treatment varied, indicating that the effects of HWT may be cultivar dependent. The incidence of P. viticola in untreated cuttings of different cultivars and from different sources was also variable. The results indicated that HWT of cuttings can be used to substantially reduce, but not eliminate, infections of P. viticola in grapevine planting material.

Observations on spot caused by Fusicladium oleagineum on olives (Olea europaea) in New South Wales, Australia

The first record of peacock spot on olives in New South Wales, Australia, was made informally in 1947 but no herbarium specimen was deposited nor descriptions made. Subsequent descriptions of this disease in Australia have been sketchy and generally reported in extension articles for olive growers. We provide here a consolidated report and description of the occurrence of Fusicladium oleagineum on the lamina, veins and petioles of leaves, fruits and pedicels of fruits of olives (Olea europaea) in New South Wales.

First report of Macrophomina phaseolina on olives (Olea europaea) in Australia

Macrophomina phaseolina was isolated from diseased olive roots. This is the first record on this host in Australia. Infection studies demonstrated that two isolates of the fungus were capable of inducing typical charcoal rot symptoms on rooted olive cuttings.