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Ongoing project

Exploring Spongospora suppressive soils in potato production (PT16002)

Key research provider: The New Zealand Institute for Plant & Food Research

What’s it all about?

This project is seeking to confirm the presence of a soil (or multiple soils) with characteristics that suppress Spongospora diseases of potato, including tuber powdery scan and root galling. If suppression is demonstrated, the project team will identify the mechanisms for suppression and determine if the suppressive properties are transferrable to non-suppressive soils, for the benefit of the Australian potato industry.

The cross-disciplinary team, including plant pathologists and soil scientists, reports that the work identifying the types of bacteria and fungi in the soil samples is continuing, with no differences yet detected between soils that are more and less suppressive of Spongospora diseases.

A second lot of experiments is now underway comparing soils of one type but with different cropping histories. Soils have been put into large pots, assessed for soilborne pathogens, fertility, microbes and structure.

Seed tubers have been planted in the pots to test for susceptibility to Spongospora diseases of potato.

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The research team have been busy measuring biological, chemical and physical soil factors in potato-growing field soils, and assessing potential mechanisms for disease suppression – while also identifying any soils that actively encourage quality- and yield-limiting diseases.

To date, 12 different soils have been analysed from cropping fields in northern New Zealand. The soils have differed in cropping history – from long-term pasture to up to three recent potato crops – and have harboured different amounts of natural Spongospora inoculum. The soils have also differed in texture, plant nutrient status, organic matter content and microbial biomass.

The soils were entered into greenhouse trials last year, being placed into large pots and planted with seed tubers of a Spongospora-susceptible potato cultivar. They were then exposed to treatments of Spongospora inoculation or non-inoculation, and subsequent plant growth, disease incidence and severity, and tuber yields were assessed. The researchers report that different amounts of Spongospora root galling and powdery scab on harvested tubers occurred in the different soils, indicating that some of them were suppressive to these diseases, while others were disease-conducive.

The work here is ongoing, with closer inspection of the soils – including DNA analysis to understand each soil’s microbial profile – and further trials set to examine those soils that have shown signs of disease suppression.

In its initial months, the project has collected 12 soils from cropping fields in northern New Zealand, where possible differences in soil conduciveness or suppressiveness to diseases caused by Spongospora have been noted. The collected soils represent different soil types and cropping histories, and some having shown potential disease suppression.

The soils have been entered into greenhouse trials which, over their course, will look at the extent of possible disease suppression. Spongospora inoculation treatments have been applied to pots of the soils, and seed tubers planted. When harvested, assessments will be made of the severity of the development of Spongospora diseases.

Soil samples have also undergone testing to characterise their physical, biological and chemical properties.

Soils that show signs of soilborne disease suppression will progress into the second phase of the project in due course, where the project team will seek to identify mechanisms of this action. If biological, they may be transferrable or, if chemical or physical, they may be manipulable in other soils.

Details

This project is a strategic levy investment in both the Hort Innovation Potato – Fresh and Potato – Processing Funds