Do some potato-growing soils suppress powdery scab?

A research project in New Zealand is determining if different field soils affect development of powdery scab on potatoes, and whether soil physical, chemical and/or biological characteristics influence this important potato disease.

The project is developing new knowledge that may provide a basis for manipulating soil factors to reduce the harmful effects of the powdery scab pathogen.

Powdery scab can severely reduce the quality and marketability of seed, fresh market and processing potatoes.

The powdery scab pathogen (Spongospora subterranea) also reduces tuber yields, by disrupting root function (water and nutrient uptake) in actively growing potato plants, and causes severe galling on roots. A research initiative that began in March 2016 aims to identify soil factors that influence development of powdery scab in potato crops.

The study involves scientists at the New Zealand Institute for Plant & Food Research Limited, and is funded as project PT16002 by Horticulture Innovation Australia Limited (Hort Innovation) and Potatoes New Zealand Incorporated.

Previous results from a long-term potato/onion trial carried out in the Pukekohe vegetable-growing region near Auckland, New Zealand, indicated that continuous potato cropping over ten growing seasons (years) did not result in increased incidence or severity of powdery scab on harvested potatoes. This suggested that the trial site soil was “suppressive” to the powdery scab pathogen. Multiple potato cropping is usually associated with severe outbreaks of powdery scab, particularly in potato cultivars that are susceptible to the disease and to Spongospora root infection.

Data gathered from these different analyses will be integrated to determine if individual or combinations of soil physical, chemical or biological characteristics are associated with suppression of Spongospora diseases.

The next phase of the project will determine details of the microbial populations in the soils, and will then identify individual disease-affecting soil factors that could be manipulated to reduce disease.

These will then be tested for effects on powdery scab and associated root diseases.

The key outcome from this project will be new knowledge on which soil factors affect powdery scab in potato crops. This could form the basis for future research initiatives, to test new practical methods for management of root and tuber diseases caused by the powdery scab pathogen.

Manipulating soil nutrients or microbial populations could be used to enhance suppression of these key potato diseases.