Case study: Research into mungbean mildew solves 60-year mystery

Read about new research revealing the source of mungbean mildew.

Background

Mungbeans have a lower fertiliser requirement than many other summer crop choices. Also they have the added benefit of fixing nitrogen into the soil, which is then available to the following crop. These factors lead to healthier soils, improved Reef water quality and greater productivity from the next crop in that ground.

However, powdery mildew can be a significant threat to mungbean production, with the potential to cause more than 40% yield losses. This can be very costly to Australian growers, who are mainly based in Queensland and northern New South Wales.

Although powdery mildew has been present in Australia for at least 60 years, we have only recently identified the precise pathogens that cause it.

Purpose

The goal was to identify the powdery mildew species infecting mungbean, black gram and wild mungbean (V. radiata ssp. sublobata) in Australia.

When

Research took place between 2017 and 2020. The research paper was published in September 2021.

Location

Toowoomba

Who

Lisa Kelly, plant pathologist at the Department of Agriculture and Fisheries, collaborated with researchers at the University of Southern Queensland.

Research

Leaves, stems, and pods of mungbean, black gram, and wild mungbean plants with symptoms of powdery mildew were collected from 34 field sites throughout Queensland and Western Australia in 2017, 2018, 2019 and 2020. We also examined 15 historical powdery mildew specimens dating back to 1965.

The pathogen species were identified by examining specimens under a powerful microscope based on morphological features and through DNA sequencing.

The identified species were isolated and then inoculated onto fresh mungbean and black gram plants to prove that the species were in fact causing disease.

Outcome

Investigations found that 2 pathogens cause powdery mildew in mungbeans and black gram, potentially unlocking new solutions for the Australian industry, worth about $100 million.

Previously only one pathogen was suspected—Podosphaera xanthii. This research confirmed a second culprit and a newly described species—Erysiphe vignae sp. Nov.

Accurate identification of the species causing powdery mildew means growers can better manage the risk of fungicide resistance. Monitoring changes in fungicide resistance can now be targeted at the 2 species separately.

Additionally, mungbean breeders can now more accurately target the pathogens for host resistance.

In the future, growers will have access to cultivars with improved resistance to both pathogens, ultimately leading to fewer fungicide applications and less run-off into waterways and the Reef catchments.

Scientists around the world who work on mungbeans will also be able to see whether the newly discovered Erysiphe vignae infects crops outside of Australia.

Host resistance and host range testing are underway with further results expected in 2022.

Media release

Sleuth scientist solves mystery of the mouldy mungbean

Research paper

This research was published in the international journal Phytopathology