20 August 2012

Say no to botrytized wines? Biological control of Botrytis cinerea in vines


This blog post was written by postgraduate student Wei Liu as part of the course, Research Methods in Ecology (Ecol608). Wei revisits a Lincoln University study on biological control in grapes published in 1999 and assesses the progress made since then.

If you think it’s weird to see your friends appreciate red wines with heavy bitterness and astringency, I strongly recommend you try noble rot wine, a famous wine with particular sweetness, made from botrytized grapes. Noble rot wine is a special product, but we do not want all the grapes to be botrytized!
 Botrytis (noble rot) shrivels the grapes, concentrating their
 sugar and flavour, and lends unique flavours to the wine (by stoneboatvineyards)

Winemakers don’t set out to make noble rot wine. Grapes occasionally become infected with Botrytis cinerea, a kind of fungus. The crop yield of grapes suffers as a result. Botrytis cinerea usually happens during wet weather just prior to harvest. After harvesting, the pathogen survives on rotten canes and leaves in the vineyard floor, or infected tissues of the vines. Then they become active again next season!

During the growing season, one of the key controlling methods is applications of fungicides. However, Botrytis cinerea will become resistant to fungicides over time, and pesticide residues in grapes are harmful to human healthy as well.
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In 1999, S.R. Fowler and other Lincoln University staffs published an article about biological control using antagonistic fungi for the control of Botrytis cinerea. In their experiment, Epicoccum sp., Scytalidium sp. and Ulocladium sp. suppressed Botrytis cinerea effectively. The suppression was via competition for nutrients and space between antagonistic fungi and Botrytis cinerea, and production of toxic metabolites to Botrytis cinerea. There were some limitations to this research. This study was done only in two places: a vineyard of Lincoln University and one in Napier, and the only factor studied was in suppressing the sporulation of Botrytis cinerea on rachii of grapes.

How time flies! A research paper published in 2011 reported that Epicoccum is currently being developed commercially as a biological control method. Because Epicoccum produces metabolites which are toxic to Botrytis cinerea.

Another article published recently studied the infection of Botrytis cinerea on grapevine debris left on the ground of vineyard and inside the canopy in vineyards of Marlborough, New Zealand. Fowler’s method of measuring the severity of Botrytis cinerea, which was published in his article mentioned above, was used in this experiment.

The Botrytis cinerea problem in wine industry is a worldwide issue, but especially in New Zealand, which has a relative warm and wet winter that suits Botrytis cinerea. More advances in Botrytis cinerea control will benefit wine industry more. On one hand, unnecessary Botrytis cinerea infection could be better controlled. On the other hand, we would be able to make noble rot wine in New Zealand, and would not need to buy as much noble rot wine from France! We could just drop down to a local winery and enjoy the kiwi noble rot wine!
 

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