Poster Presentation Science Protecting Plant Health 2017

Influence of high and low levels of potassium in field soil on common scab symptom development – a glasshouse experiment (#145)

Tonya J Wiechel 1 , Justin Verstraten 1 , Greg Patterson 2
  1. AgriBio, Centre for AgriBioscience, Agriculture Victoria, Bundoora, VIC, Australia
  2. A&L Canada Laboratories, London, Ontario, Canada

Common scab, caused by pathogenic strains of Streptomyces scabies, is an important disease in potato worldwide that affects the quality of the potato by producing superficial, raised and deep pitted lesions on the tuber surface. Anecdotal evidence from potato growers suggests that soil that has had a high level of dairy manure deposited in holding yards near a dairy shed and areas of field that have had wood piles burnt get increased common scab. Both these scenarios produce elevated levels of potassium in soils. We identified a field in the Koo Wee Rup region with a common scab hotspot. To better understand why some potato fields get common scab and others do not, we sought to characterise the soil inside and outside the hotspot. Soil nutrient analysis found elevated levels of potassium in the hotspot (13%) compared with 4.5% outside the hotspot. Field soil was collected and a glasshouse trial was established to reduce the level of K in the hotspot soil by treatment with either gypsum (CaSO4) or lime (CaCO3), and increase the level of K in soil collected from outside the hotspot with the addition of murate of potash (KCl). We demonstrated that the addition of inoculum at planting produced common scab in all soils except those with low K + KCl. DNA analysis of harvest soil found pathogen DNA in all inoculated treatments. Common scab was significantly reduced in hotspot (high K) soil by the addition of gypsum and lime. Further studies are required to understand the mechanism of control.