Research update on grapevine trunk diseases in New Zealand
1 August, 2008
Establishing how Blackfoot and other grapevine trunk diseases are spread
Petri disease causes the gradual decline in vigour and productivity of infected vines. The disease is common overseas and has become more prevalent in New Zealand in recent years. Sonya Whiteman of Lincoln University conducted research on the influence of nursery practices on the spread of Petri disease. She showed that Petri disease could be transferred from infected rootstock vines to new grafted vines and that hydration tanks used during grafting were a significant source of contamination. Dr Anna Graham from Corbans Viticulture undertook further research and discovered that vines with low to moderate levels of Petri disease infection did not always show symptoms and could therefore pass unnoticed through the nursery grading procedure.
A survey conducted by Dr Marlene Jaspers of Lincoln University showed that blackfoot disease, caused by Cylindrocarpon was present in all viticulture regions in New Zealand, but most commonly reported in Marlborough. It was most commonly reported in young vines of less than five years old and affected vines planted on a range of different rootstock. The symptoms of blackfoot disease include delayed budburst, with gradual stunting and decline in vigour followed by early scenescence and sometime eventual death of the vine.
Carolyn Bleach from Lincoln University has found and identified three species of Cylindrocarpon in New Zealand grapevines - Cylindrocarpon destructans, C. macrodidymum and C. liriodendri. Of the three species, C. liriodendri is the most virulent. Callused cuttings planted in the nursery were three times more likely to become infected by the soil-borne pathogens than young rooted cuttings planted in a vineyard.
Botryosphaeria is another grapevine trunk disease of significance overseas and more recently in New Zealand. Nicholas Amponash of Lincoln University is undergoing a PhD project on development and spread of Botryosphaeria disease in grapevines in New Zealand. He has found that Botryosphaeria infection traveled up the trunk of the vine faster than downwards. Visual symptoms of dieback did not occur until the disease had progressed to the tip of the shoots. This disease tends to affect vines that are at least eight years old or in younger vines that have been subjected to stress. In 2006, he surveyed vines and potential alternate hosts surrounding vineyards in Marlborough, Canterbury, Nelson, Gisborne and Auckland for Botryosphaeria disease. Botryosphaeria species were found in willow, native Ngaio, pine and several orchard trees. Several Botryosphaeria species were isolated mostly from woody tissue of older vines, and to a lesser extent from leaves, flowers, weak buds and green shoots. The more virulent
B. lutea and B. parva were found more commonly in the North Island, whereas
B. stevensii and B. obtusa were more common in Blenheim and Nelson.
Developing PCR techniques to diagnose trunk diseases
A group at Lincoln University lead by Hayley Ridgway is in the process of developing species specific markers for PCR detection of trunk diseases including Cylindrocarpon, Botryosphaeria and Phaeomoniella chlamydospora. The earliest work was completed in 2004 by Sonya Whiteman who developed PCR markers unique to Phaeomoniella chlamydospora. Her techniques allow for very sensitive detection of this disease in soils and rootstock used for grafting. Chantal Probst is currently working on the development of similar PCR probes to distinguish the different Cylindrocarpon species found in New Zealand.
Jayaseelan Baskarathevan has a PhD project aiming to develop PCR-based identification tools for the 13 species of Botryosphaeria known to cause disease in grapevines.
In 2007, Jason Shiller at the University of Auckland developed a single PCR method for detecting Petri disease and Phomopsis species and Eutypa in young vines.
Bevan Weir, in association with Corbans Viticulture and Landcare has developed another PCR method that detects several fungal species at once. These tools will be useful to nurseries to monitor infection s in young vines before symptoms develop.
Developing methods for the Control of grapevine trunk diseases
Hot water treatment, also known as HWT, is method developed overseas to treat grafting material grown in hot climates. It was found to significantly reduce the incidence of a range of fungi and bacteria causing trunk and root diseases. However, the protocols developed overseas were not suitable for New Zealand’s cooler climate. Dr Anna Graham, from Corbans Viticulture developed a HWT protocol suitable for cool climate viticulture. This method is effective for reducing Petri disease infection in grafting material and nursery vines. Subsequent trials have showed that HWT in conjunction with a range of soil amendments such as Trichoderma, mycorrhizal products, Mycorrcin™, Biolplex™ containing fish hydrolysate reduce pathogen incidence in young vines while increasing vine growth.
Carolyn Bleach from Lincoln University has conducted field trials at Corbans Viticulture nursery on control of Cylindrocarpon Blackfoot in young vines. Control methods tested have ranged from soil fumigation and fungicides to bio-control with use of plants and micro-organisms, use of mulches and active compost, and HWT. Hot water treatment was the most effective method of those trialed for control of Cylindrocarpon in young vines. This agrees with similar trials conducted in South Africa which found that HWT of dormant vines was the most effective control for Cylindrocarpon.
Fig 1.0 Incidence and severity of Cylindrocarpon with different treatments
Isolations from trunks showed that HWT was similarly effective in plants assessed immediately or grown in pots for 6 months, having 6-13% severity compared to 38-72% in control plants.
Regina Billones of Lincoln University has started a PhD project on inoculum sources for Botryosphaeria and effective control strategies for grapevine nurseries. She will investigate the use of HWT for control of Botryosphaeria in grafting material and in young vines.
Research updates are presented to the industry at the annual Bragato conference. In 2004 and 2005, Sonya Whiteman and Dr Anna Graham presented their work on Petri disease. In 2006, Carolyn Bleach and Chantal Probst reported their work on Cylindrocarpon. This year Nicholas Amponash will present a talk on Botryosphaeria.
As evident above a significant amount of viticulture research is currently being undertaken in New Zealand. Hopefully the benefits of this research will soon be evident in the bottle.
