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Australasian Plant Pathology Volume 31, 2002 © Australasian Plant Pathology Society 2002 A journal for the publication of original research in all branches of plant pathology
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Australasian Plant Pathology, 2002, 31, 193–194
DISEASE NOTES OR NEW RECORDS An unusual bunch rot of grapes in sub-tropical regions of Australia caused by Colletotrichum acutatum Kevin J. Melksham, Melanie A. Weckert and Christopher C. SteelA National Wine & Grape Industry Centre, School of Wine and Food Sciences, Charles Sturt University, PO Box 588, Wagga Wagga, NSW 2678, Australia. A Corresponding author; email:
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Abstract. An unusual bunch rot of wine grapes in the Hunter and Hastings Valleys of New South Wales (NSW) was identified as being caused by Colletotrichum acutatum. Symptoms included a salmon-pink discharge of conidia from infected fruit and a characteristic bitter taint to both grapes and wine. The disease was found to be widespread in sub-tropical grape growing regions of NSW. This is believed to be the first report of Colletotrichum acutatum on Vitis vinifera in Australia. AP02013 K. J.Melksham, M.A. Wecekrtand C.C.Stel
K.JMelksham etal.
Fungal rots of grapevine berries (Vitis vinifera) are a serious limiting factor in wine production worldwide. In recent years, a berry rot of grapes has been observed in sub-tropical regions of Australia with symptoms uncharacteristic of the known fungal pathogens of winegrapes. Initial symptoms include a loss of berry turgor with a characteristic bitter taint to the fruit. Stems of bunches may also be affected. As the disease progresses, a salmon-pink coloured discharge of conidia is observed. Berry drop can occur in infected bunches and yield is affected. The taint that this organism produces in the fruit is also found in wine made from infected grapes. As the taint is difficult to correct, this results in wine of an inferior quality. Furthermore, non-traditional wine grape cultivars are affected to the same extent as V. vinifera. Symptoms of this rot have been observed in vineyards in Mudgee, Tenterfield, in the Hunter and Hastings Valleys of New South Wales and at Stanthorpe, Queensland. Occurrence is related to wet, humid conditions at flowering and at harvest. Our initial observations indicate that vineyard practices used to control Botrytis cinerea (a common cause of bunch rot of grapes), such as an open canopy, actually favour development of this non-Botrytis bunch rot. Furthermore, fungicides used to control B. cinerea appear to be ineffective against this particular organism. The organism was isolated from V. vinifera berries from a number of cultivars, including Cabernet Sauvignon, Merlot, Pinot Noir and Shiraz and also from berries of Chambourcin, a V. vinifera hybrid of mixed parentage, close to harvest (Brix > 20 in all cases). The organism was also isolated from stems and rachises of these grapes. The salmon-pink discharge observed on infected plant material was transferred to plates of potato-dextrose agar amended with lactic acid (LAPDA) using a sterile needle. Cultures were incubated for 7 days at 25°C. All isolates grew readily on LAPDA supplemented with benomyl (10 mg/L) and iprodione (10 mg/L). The © Australasian Plant Pathology Society 2002
colony morphology was examined after incubating for 7 days in the dark, using methods based on those of Pitt and Hocking (1997). On Czapek’s yeast-agar (CYA), malt-extract agar (MEA) and PDA, abundant conidia were formed on aerial mycelium, developing from the solitary phialides of simple conidiophores (Fig. 1). Conidia were aseptate and mostly
Fig. 1. Colletotrichum acutatum (DAR 75574) showing an appresorium (A) and conidia (C) from solitary phialides (P) of simple conidiophores.
10.1071/AP02013
0815-3191/02/020193
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K. J. Melksham et al.
fusiform, i.e. cylindrical with both ends pointed, although this was variable. Conidial sizes were also variable but mostly 2.5 – 4 × 8 – 13 µm. Light orange superficial conidial masses were seen at the centre of older colonies. Mycelium was slender (2.5 µm thick) and hyaline with broader, dark, much septate mycelium (5 µm thick) appearing later. Dark terminal and intercalary chlamydospores (4.5 µm diameter) were present in older cultures from dark hyphae. Appressoria which formed on PDA slide cultures were brown, obovate (i.e. inversely ovate) and mostly simple, not lobed, 5–15 × 13–23 µm, borne on hyaline hyphae (Fig. 1). These morphological characteristics agree with those of Colletotrichum acutatum (Simmonds 1965). The identity of the organism as C. acutatum was further confirmed by Dr Michael Priest, NSW Agriculture, Orange. Although reported to occur on Vitis rotundifolia (Muscadine grapes) (Kummuang et al. 1996), and on Vitis vinifera table grapes (Yamamoto et al. 1999), we believe this to be the first report
of this organism on V. vinifera grapevine berries in Australia. An isolate of this organism (DAR 75574) has been lodged with the Plant Pathology Herbarium (DAR) at Orange, New South Wales. References Kummuang N, Smith BJ, Diehl SV, Graves CH Jr (1996) Muscadine grape berry rot diseases in Mississippi: disease identification and incidence. Plant Disease 80, 238–243. Pitt JI, Hocking AD (1997) ‘Fungi and food spoilage (2nd edn).’ (Blackie: London) Simmonds JH (1965) A study of the species of Colletotrichum causing ripe rots in Queensland. Queensland Journal of Agricultural Science 22, 437–459. Yamamoto J, Sato T, Tomioka K (1999) Occurrence of ripe rot of grapes (Vitis vinifera L.) caused by Colletotrichum acutatum Simmonds ex Simmonds. Annals of the Phytopathological Society of Japan 65, 83–86.
Accepted 7 March 2002
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