While the winegrape harvest accelerates across Australia, research at the National Wine and Grape Industry Centre (NWGIC) is arming grapegrowers and winemakers with increased knowledge about how bunch rot can impact a final wine – and how much is too much.
Led by Charles Sturt University (CSU) Professor Chris Steel, Wagga Wagga, the research, funded by Wine Australia, aims to determine thresholds for bunch rot contamination, building on an earlier project that examined Botrytis or grey mould contamination of Chardonnay grapes in 2016.
“Bunch rot, or fungal rot of wine grapes, is a worldwide problem, particularly when rain falls close to harvest,” Professor Steel said.
“Bunch rots reduce yield and can impact on wine quality by producing off flavours and taints. Growers have to decide when and if they harvest impacted fruit, and at the winery it can lead to the downgrading or possible rejection of fruit.
“This project will determine the thresholds for bunch rot contamination that can be tasted in wine, and provide grapegrowers and winemakers with tools to handle fruit when these thresholds are exceeded.”
For this vintage, the new research will be extended to include Cabernet Sauvignon grapes.
“Aside from continuing to evaluate ergosterol as a measure of fungal contamination, we will also look at other techniques including measuring gluconic acid and loop-mediated isothermal amplification (LAMP), a molecular biology based technique for detecting Botrytis in grapes,” Professor Steel said.
Wine Australia general manager of research, development and extension Dr Liz Waters said bunch rots can be a significant cost impact on grapegrowers and winemakers.
"This project is exciting because it will help us determine how much bunch rot is too much, so that an objective measure can be set to assist growers and winemakers in their decisions at harvest,” Dr Waters said.
The NWGIC is an alliance between CSU, the NSW Department of Primary Industries and the NSW Wine Industry Association.