Fungus find bitter-sweet news for pulse industry

The discovery of a mutation in the pathogenic fungus Botrytis cinerea (also known as grey mould) in an isolate from a chickpea crop has bitter-sweet implications for the pulse industry, particularly in South Australia.

While the finding has underlined the need for pulse growers to exercise strict adherence to fungicide label restrictions to reduce the potential for fungicide resistance, identification of the mutation will enable the development of better disease management strategies for growers.

The mutation has been found by researchers at Curtin University where research into fungicide resistance is led by Richard Oliver and funded by the Grains Research and Development Corporation (GRDC).

"This mutation, quite common in European vineyards, occurs in the â-tubulin gene which is the target of the methyl benzimidazole carbamates (MBC) fungicides, a very important group of anti-fungals worldwide," Professor Oliver said.

"MBC fungicides have been used for plant disease control since the late 1960s. MBC fungicides that are registered in Australia include carbendazim and thiabendazole - the latter is in P-Pickel T liquid fungicidal treatment which is recommended for all chickpea and lentil seed in the southern region of SA."

SA Research and Development Institute senior pulse pathologist Jenny Davidson said the grey mould fungus attacked chickpeas and lentils and could be found on faba beans and vetch, as well as in vineyards.

"Chickpeas in SA are rarely treated with carbendazim but usually have thiabendazole on the seed (as part of the P-Pickel T seed treatment) while most lentil and faba bean crops have at least one spray of carbendazim," Ms Davidson said.

"The label for carbendazim states that only two sprays per crop are permitted, to reduce the chance of selecting out resistant types. Farmers are well advised to stick to this strategy, particularly in light of the new finding."

Although resistance has been recorded in Australian vineyards for many years, it is the first time the mutation has been detected in a broadacre crop. The resistant strain of the fungus was isolated in 2003 in a chickpea crop at Kingsford in SA's Lower North.

Chickpea crops in this area are not heavily treated with fungicide, highlighting the very real risk of fungicide resistance and the need for the establishment of effective on-farm fungicide resistance monitoring procedures, according to Professor Oliver.

He said identification of the mutation did have positive consequences.

"It not only means that researchers now understand how grey mould becomes resistant to MBC fungicides, it also means we can help Australian pulse and grape growers to manage the disease in a better way by developing rapid analysis methods for isolates coming from crops in which growers have observed MBC control failure," he said.

"The analysis of the resistance of a bigger B. cinerea population will give us an idea of the situation of the resistance to currently used fungicides and new active ingredients to the Australian market in this pathogen."