Perhaps one of the only upsides to come from COVID-19 is the familiarity that many people now have with rapid antigen tests (RATs), and it’s this type of test that researchers and winemakers believe shows promise for quickly and cheaply quantifying Botrytis.
Over the recent harvest, winemakers and growers have been working with Professor Chris Steel from Charles Sturt University with funding from Wine Australia to evaluate a commercially produced Botrytis test kit under Australian conditions. Preliminary data of the rapid test kits shows that the results are comparable with those from more complex, time consuming or costly methods.
If found to be suitable in a wine sector setting, the kit will provide a rapid and simple method to not just detect, but also to quantify the amount of Botrytis present in grape and wine samples.
The RAT-like tests are produced by Global Access Diagnostics (GADx) with the result measured on a device called a ‘cube reader’ which fits in the palm of the hand and estimates the amount of Botrytis present in a grape sample in ten minutes.
“For the first time growers and winemakers can specifically and rapidly detect botrytis bunch rot in grapes in the vineyard,” said lead researcher, Professor Steel.
“Being able to quantify Boytytis bunch rot contamination in real-time empowers winegrape growers, agronomists and scientists to objectively make management decisions.”
Professor Steel said unlike other rapid methods for fungal detection such as PCR, the antigen detection requires a relatively low level of operator skill.
“Grape samples are crushed and then a test strip is placed in the juice. The test strip is then inserted into the cube reader, and after 10 minutes a numerical result is obtained.”
In association with the research team at Charles Sturt University, a number of wineries are currently evaluating the applicability of the method in a winery setting.
“Participating wineries are comparing the GADx antigen detection kit with their existing methods of Botrytis estimation at the winery receival area during vintage,” said Professor Steel.
“Preliminary data indicates that results obtained by the GADx kit are comparable with existing methods for Botrytis contamination of grape samples.”
Professor Steel said the findings were exciting, because bunch rot caused by Botrytis was a serious problem in some vintages, particularly when rain falls close to harvest. Aside from a loss of grape yield, the fungus has a negative effect on quality.
The 2023 vintage year has been particularly challenging, with some wine regions experiencing wetter conditions than usual leading to higher rates of fungal growth like botrytis and loss of yield and effect on quality.
Professor Steel said detection of the Botrytis fungus with the naked eye is difficult, as it is often hidden from view within the interior of the bunch.
Image: AdobeStock
More accurate methods of Botrytis generally involve longer analysis times and access to sophisticated laboratory equipment and the necessary skill set to perform the analysis.
“Requiring time frames of hours or even days for analysis, the applicability of these alternative methods for Botrytis estimation in a wine sector setting during the busy vintage period is limited.
“On the other hand, the GADx kit has the potential to provide a quantitative estimate within a matter of minutes. The portability of the cube reader means that analysis can easily be conducted in a winery or vineyard setting.”
Professor Steel said the technology had the potential to improve both the accuracy of Botrytis determination as well as the turn-around for samples.