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3rd International Powdery Scab Workshop, Einsiedeln, Switzerland 17th – 21st July 2016
The 3rd International powdery scab workshop was hosted by Dr Ueli Merz, ETH Zurich, with 21 participants from 12 countries. Powdery scab remains an important disease of potato worldwide, causing significant economic losses.
However, the research effort is relatively limited compared with other potato diseases, no doubt in part due to the challenges of working with Spongospora subterranea. The causal organism of powdery scab and root galling in potato is biotrophic, soil-borne, has a complex and still incompletely described lifecycle and is also the vector of Potato mop-top virus. Potato pathologists, agronomists and breeders with an interest in powdery scab meet every 2-3 years at European or International workshops to review progress, present new findings and discuss the subject indepth.
Host resistance to powdery scab is one of the few very effective ways of controlling the disease and amongst several talks describing breeding and screening for resistance, I found the talk of Jose Miguel Cotes and Paola Gonzalez Jaimes ‘Development of five Solanum phureja varieties resistant to powdery scab’ of particular interest. Paola described the problems caused by powdery scab and late blight in Colombia and work to evaluate germplasm for resistance to powdery scab and root galling in soils with massive natural inoculum concentrations. Finally she presented the five resistant S. phureja varieties resulting from the work.
In addition to the visible powdery scab symptoms on tubers and root galls, S. subterranea infects roots, resulting in disrupted root function. Richard Falloon’s presentation considered the contribution of diseases caused by S. subterranea as components of suboptimum potato yields in New Zealand.
Work in NZ showed that fungicidal control of the incidence of powdery scab resulted in increased yields and S. sub- terranea was shown to reduce root function, water use and growth of potato plants, independent of cultivar susceptibility to powdery scab. Field assessments showed that soil-borne diseases are key causes of sub-optimum potato yields in NZ and Spongospora root diseases are commonly severe in potato crops.
The workshop included an excursion to The Swiss Agricultural College at Zollikofen where the participants were given an introductory talk by Andreas Keiser and were able to view plot trials on powdery scab, Dickeya/Pectobacterium and black dot first hand. After lunch, taken in beautiful surroundings with a superb view of the north face of the Eiger, Adrian Kraehenbuehl from SEMAG, a grower cooperative, gave a very interesting overview of seed production in Switzerland with a visit to field plots and a seed farm.
On the final morning of the workshop the participants together reviewed knowledge and progress that may contribute to the improved control of powdery scab. This includes improved disease prediction through knowledge of sources of contamination, soil inoculum levels and their relationship with disease development, symptom identification, breeding for disease resistance and chemical control. It is clear that progress in powdery scab research is always incremental and an integrated management approach is key.
Thanks to Ueli Merz for organising another excellent meeting and for his enthusiasm in bringing together powdery scab researchers in meetings and project collaborations over many years. We wish him well in his retirement. For anyone interested in Spongospora, Ueli’s webpage (http:// www. spongospora. ethz. ch/) will still be available.
I would like to thank the British Society for Plant Pathology for their financial support which allowed me to attend this workshop. I was able to present 2 talks, the first ‘New insights into the life cycle of S. subterranea; a microscopical study’ made on behalf of my colleague Alison Roberts at The James Hutton Institute and the second ‘Research on infection by S. subterranea and host resistance to powdery scab’, and to participate in the wide-ranging discussions.
Alison Lees The James Hutton Institute