The behaviour of populations of potato cyst eelworm Heterodera rostochiensis Woll. Towards resistant potato varieties derived from Solarium tuberosum ssp. andigena Juz & Buk

Abstract

SUMMARYMany populations of Heterodera rostochiensis mostly from the main potato growing areas of England and Wales, were tested with eelworm‐resistant potato varieties (andigena hybrids). Except in the Eastern Region, where resistant varieties were planted alongside commercial varieties in infested fields, tests were done in pots inoculated with a standard number of cysts extracted from a single soil sample from each field. The tests showed that England and Wales could be divided into areas according to the percentage of cysts(< 10%, 11–70%,> 70%) produced on the resistant compared with a commercial non‐resistant variety. On the peat soils of the East Anglian fens and in Bedfordshire, Essex and Kent (area A) most populations produce few cysts on resistant varieties. In much of the East Midlands and Yorkshire (area D), populations produce many cysts on resistant varieties which behave much as ordinary susceptible potatoes. Populations in the rest of England and Wales (areas B, C) vary and in many districts every field must be tested separately.If the pathotypes occurring in Britain had separate origins in South America, the present distribution in England and Wales is probably due to chance introductions dispersed with seed and following the patterns of trade in seed potatoes. As all commercial varieties, before the release of eelworm‐resistant ones, were about equally susceptible to the different pathotypes, the varieties themselves probably played little part in determining the present distribution of pathotypes.