Effect of temperature on Botrytis cinerea, Colletotrichum acutatum and Greeneria uvicola mixed fungal infection of Vitis vinifera grape berries

Detached Vitis vinifera 'Cabernet Sauvignon' berries (12.5° Bé) were inoculated either singularly or in combination with spore suspensions of Botrytis cinerea, Colletotrichum acutatum and Greeneria uvicola and the degree of disease expression examined at either 20 or 27 °C. Berries were more susceptible to B. cinerea at 20 °C and to G. uvicola at 27 °C but were highly susceptible to C. acutatum at either temperature. In experiments involving inoculation of berries with mixtures of fungal organisms, B. cinerea infection was diminished at 27 °C by either C. acutatum or G. uvicola but only by C. acutatum at 20 °C. G. uvicola infection was diminished by C. acutatum at both temperatures investigated. B. cinerea reduced the level of infection of both C. acutatum and G. uvicola at 20 °C. The findings have implications for seasonal bunch rot management of grapes in relation to predicted changes in global temperature

Overwintering and presence of Colletotrichum acutatum (ripe rot) on mummified bunches, dormant wood, developing tissues and mature berries of Vitis vinifera

Colletotrichum acutatum, the casual agent of ripe rot in tropical and sub-tropical grape growing regions of Australia, affects crop yield and wine quality. To elucidate the epidemiology of the fungus, its presence was studied on shoots, pea sized and mature berries, mummified bunches, spurs and canes during two consecutive growing seasons and one winter season. The presence of C. acutatum was analysed by both traditional and real-time PCR methods. A protocol was developed to achieve PCR amplification for fungal DNA extracted from 'difficult' wood samples. C. acutatum was detected on mature berries, mummified berries, the peduncles of mummified berries, winter spurs and canes but not on the remaining analysed tissues. Thus the fungus overwinters on Vitis vinifera plant tissues and the conidia on spurs and dormant wood are likely to be the most important source of primary inoculum for the next growing season.

Pathogenicity of Botryosphaeria species isolated from declining grapevines in sub tropical regions of Eastern Australia

From 2002 to 2004, vines from 11 vineyards in the Hunter Valley region and from 4 vineyards in Mudgee (New South Wales, Australia) were inspected for foliar and wood symptoms of Eutypa dieback and Botryosphaeria canker. Eutypa lata was not isolated, however species of Botryosphaeria were frequently isolated from dead and declining spurs, cordons and trunks. Two species conforming to the anamorphs of Diplodia and Fusicoccum were isolated. Cultures on PDA producing a yellow pigment, and hyaline aseptate conidia (14-23.5 x 8-13 μm in size) were identified as B. lutea. Cultures with dark brown, 1-septate, ornamented conidia (15-25 x 8-14 μm in size) at maturity were identified as B. obtusa. Pathogenicity tests were conducted on detached green shoots, detached one-year-old canes and glasshouse-grown grapevines. In all situations, disease symptoms were reproduced and Koch’s postulates were fulfilled. The results demonstrate the potential of B. obtusa and B. lutea as primary pathogens of Vitis vinifera.

Association of Botryosphaeriaceae grapevine trunk disease fungi with the reproductive structures of Vitis vinifera

Several species belonging to the Botryosphaeriaceae were isolated from grapevine (Vitis vinifera) tissue other than wood during a survey of two vineyards planted to cultivars ‘Chardonnay’ and ‘Shiraz’ in the Hunter Valley, New South Wales, Australia over the 2007/08 and 2008/09 growing seasons. A total of 188 isolates corresponding to nine different species of Diplodia, Dothiorella and Neofusicoccum anamorphs were isolated from dormant buds, flowers, pea-sized berries and mature berries prior to harvest in addition to 142 isolates from the trunks of the same vines. Furthermore, the occurrence of Dothiorella viticola, Diplodia mutila and Neofusicoccum australe is reported here for the first time from grapevines in the Hunter Valley. These findings may provide important information for the management and spread of Botryosphaeriaceae in vineyards where they are considered serious wood-invading pathogens. Botryosphaeriaceae are occasionally found on bunches, however, until now they have not directly been related  to bunch rots. Control strategies for trunk diseases caused by Botryosphaeriaceae are currently limited to remedial surgery and wound protection. These strategies do not consider other grapevine tissue as potential inoculum sources for infection of Botryosphaeriaceae in the vineyard.

In vitro systems for studying the interaction of root-knot nematode with grapevine

The original publication can be found at www.springerlink.comA simple system for in vitro dual culture of grapevine (Vitis spp.) plantlets and root-knot nematode (Meloidogyne javanica (Treub) Chitwood) is described. Based on the presence or absence of mature females, or the total number of nematodes in the roots after 36-day co-culture, the system reliably discriminated resistant (cv. Ramsey) and susceptible (cv. Chardonnay) grapevines. The system was sensitive enough to differentiate between infestation levels of cvs Borner and Chardonnay, both susceptible in the in vitro conditions. A modification of the system to use plantlets from rooted petioles has reduced labour and space requirements and would suit mass screening of grapevine genotypes in traditional or genetic engineering-based breeding programmes. In both systems, nematodes in roots of cv. Ramsey tended to be associated with brown tissue and, compared with those in roots of cv. Chardonnay, were more likely to be con. ned to tips rather than be distributed along the root after co-culture for 11 or 36 days.Tricia K. Franks, Sandra Savocchia and Robyn Van Heeswijc

Organic control of grapevine powdery mildew in Eastern Australia

http://www.safecrop.org/english/events/pdmildew2006

Survey of Botryosphaeriaceae associated with grapevine decline in the Hunter Valley and Mudgee grape growing regions of New South Wales

Species belonging to the fungal family Botryosphaeriaceae are important pathogens of grapevines in Australia. A survey of declining grapevines inthe Hunter Valley and Mudgee grape growing regions of New South Wales revealed 36% were infected with species belonging to the Botryosphaeriaceae. Theincidence of Diplodia seriata was greatest, followed by Neofusicoccum parvum, Botryosphaeria dothidea and Lasiodiplodia theobromae. These identifications were made using a combination of molecular and morphological characters. Although D. seriata was the most common species found, its role as a primary pathogen of grapevines in Australia is yet to be ascertained. The accuracy of estimating the incidence of species was increased by surveying up to 25 grapevines per vineyard and by sampling both the trunks and cordons. Other pathogens capable of causing trunk diseases were also isolated in this survey, demonstrating that diagnosis based on symptoms alone is not sufficient and isolations on artificial media and sometimes DNA sequencing are required for a definitive diagnosis of the causal organism of decline