Clay spray set to fight grape rot

Researchers at the Tasmanian Institute of Agriculture are leading a world-first project to investigate the use of BioClay to supress botrytis bunch rot disease in wine grapes.

It could be a game-changer for the wine industry, offering an innovative alternative to chemical fungicides. Working on the project are Professor Kathy Evans, Dr Tory Clarke, and PhD student Akeem Taiwo.

“This is the first time in the world the BioClay technology is being tested for suppression of botrytis in wine grapes. The goal of our project is to investigate how the technology can work in this crop, and this will support the long-term development of a potential product for use here in Tasmania and around the world,” Dr Clarke said.

It is estimated the processed value of wine grapes in Tas- mania could be 24 per cent higher if costs due to botrytis disease are recuperated.

BioClay is a biodegradable spray solution of clay particles that binds double-stranded (ds) RNA and releases it slowly, working with the plant’s naturally occurring mechanisms to stimulate the immune system.

“At the moment we are working without the clay component to confirm the RNA science works in grapevines.

We are treating grape berries with the dsRNA product and then inoculating the berries with the botrytis fungus,” Dr Clarke said.

She said botrytis bunch rot was a major challenge for growers as it results in major yield losses and could lead to problems during winemaking despite management practices during the season.

“Botrytis can be triggered by weather events like rainfall in the weeks leading to harvest. Mould can appear really quickly, and you can go from having perfect grapes to losing your crop in a matter of days,” Dr Clarke said.

While the disease is seen in ripening fruit, infection may have occurred in flowers or unripe fruit so the team has set up a novel system to have access to flowering grapevines all year. “Wine grape plants flower just once a year. We know that floweringisacriticalpointin the disease development and so we’ve set up a system where wecanhaveaccesstoflowering grapevines all the time.

“We propagate commercial cuttings of vines, get their roots growing and then put them in the glasshouse where we control temperature and light to

replicate flowering conditions. “Our little grapevines think it’s spring and start flowering. It takes around four months from cuttings to having vines with berries, but we now have regular batches of plants which flower and produce grape berries.”

The research team now need to inoculate the plants with botrytis so they can further test and develop the BioClay product.

“We will inoculate plants by puffing spores onto the flowers or fruit to replicate what would happen in the environment where spores would be in the air,” Dr Clarke said.

“It will be interesting to see the results because coupling dsRNA to a clay stabilises it and results in a sustained release, so we can get longer protection for the crop compared to current chemical solutions that might be washed away by rain.”

The final part of this project will involve working with growers and testing the technology in commercial vineyards, which may be several years away.

Professor Evans said producers were desperate for more options to control botrytis.

“Good viticultural practices can counter some of the bad weather; however, a well-timed crop protectant can make the difference.”