What was it all about?

Powdery scab disease of potato is a common blemish disease that affects potato roots and can result in significant yield losses and impact on the economic competitiveness of the industry. This project ran from 2014 to 2017 and improved current understanding of the pathogen that causes powdery scab. It found that any treatment that delays initial onset of root infection (such as reducing soil inoculum, chemical treatments, and developing host resistance) will delay or slow the infection cycle, leading to reduced root infection, reduced impact on plant growth, and reduced subsequent tuber disease.

The project investigated the lifecycle of the pathogen including how its spores can enter a dormant phase within the soil, how chemicals released by the roots of the host plant can cause spore germination, and how released spores are then attracted to the host’s roots via these same chemicals. The influence of variety, plant stress and environment on these processes was also examined.

The project team identified opportunities for improved disease management, however they noted that further work would need to be done to refine these tools for commercial use. Some findings that are suitable for adoption by industry include:

• Monitoring root infection. The project developed new detection methods that can be used to identify early onset of infection, with the research noting that delaying infection can alter the overall progression of the disease. The monitoring approaches will be useful in any future research to test the effectiveness of chemical treatments and the resistance of new varieties, and complements direct microscopic examination of root infections. The project also developed a new lab test that quantifies infection in roots, which means that the impact of management strategies in reducing or delaying root infection can be properly measured in future research. Further information on these tests can be found in the full final research report, which can be downloaded above.

• Resistant varieties. The project conducted trials on resistance to root infection and galling. This identified some varieties with enhanced (but not complete) resistance that could be used by growers as a management tool. This included a number of publicly available cultivars and further details can be found in the final report available for download above.

• Alternate hosts (weeds and cropping species). Weed control and volunteer potato control are essential as many weed species have been noted to increase and/or sustain soilborne powdery scab levels. These species include blackberry nightshade, sow bane, sow thistle, hedge mustard and clustered dock. Additionally, the crop species, opium poppy and pyrethrum, were shown to partially support powdery scab. Consideration of rotation scheduling should be given to avoid planting crops prior to potato that exacerbate inoculum levels.

As fungicides have limited impact on dormant spores, the project also conducted field trials on the use of stimulatory compounds that encourage spore germination whilst there is an absence of suitable host plants. Active spores only persist for a few hours in the soil without a host, so this method could potentially be used to deplete soil pathogen inoculum.

ACT NOW

Watch the lead researcher of this project, Professor Calum Wilson, present to industry on the recent advancements in tackling both powdery and common scab of potato.

Read an article in Potatoes Australia that summarises the projects findings.