Quick Dips

Useful Yeasts

Yeasts from foods like Vegemite, bread and yoghurt are being examined to see if they can be used to stop fungi growing on fresh fruit and vegetables. This approach is the latest research undertaken by Dr Charles Wilson of the Appalachian Fruit Research Centre. He is in New Zealand for two months, working with Dr Lian-Heng Cheah at Crop & Food Research's Levin Research Centre.

They have successfully developed a rapid screening process for identifying yeasts that have the properties needed for biocontrol agents of diseases in fruit and vegetables.

"We've isolated a yeast in Vegemite that looks pretty good and Dr Cheah has found one in yoghurt that also looks promising," Wilson says.

Wilson and Cheah have collaborated for several years and are continuing to look for non-chemical solutions to prevent disease or rots on fresh produce.

As well as screening yeasts, the pair are investigating the use of ultraviolet light treatments to "switch on" disease resistance in fresh produce and they are looking for strains of pathogens, like botrytis, which do not cause disease. Cheah's collection of 60 strains of botrytis is being screened at Levin; any strains that don't cause disease will be tested for their ability to protect against disease-causing types.

Wilson is a world-renowned pathologist who was the first research scientist to patent a biological agent, a yeast which shows control of postharvest rots in citrus fruits and apples.

He says he was initially repelled by the idea of patenting organisms, particularly because it inhibited the free exchange of ideas between scientists. However, Wilson has come to realise that it is necessary for companies to have priority rights to make it worth their while to commercialise an organism.

"The moral issue for me is that we should not deny the public the right to something that is more helpful and useful than it would be if left in nature," Wilson says.

He has also patented a bacteria, Baccillus subtilis, which acts as a biological control agent for rot diseases on peaches and bananas after harvest. Wilson compares the introduction of biocontrol agents for the control of postharvest produce to the introduction of the first aeroplane.

"It's a nerve-wracking and exciting time," he says.