Spatial distribution and basic ecology of Heterodera schachtii and H. betae wild populations developing on sea beet, Beta vulgaris ssp. maritima

Abstract

Most populations of crop pathogens have wild relative populations from which they can originate but for which basic knowledge of their ecological requirementsin naturais scarce. However, the study of spatial distribution and ecology of wild pathogen populations may help control them in crops through a better understanding of the environmental factors driving population dynamics. Here, we focused onHeterodera schachtiiandH. betae, two cyst nematodes that cause severe damage to sugar beet (Beta vulgarisssp.vulgaris) crops and can develop on a wild beet relative, the sea beet (B. vulgarisssp.maritima). We investigated the occurrence of both nematode species in the wild and explored some environmental factors that may influence their geographical distribution. To do so, we sampled the wild hostB. v.ssp.maritimaalong the European Atlantic and North Sea coastlines. Results showed thatH. schachtiimainly occurred in the colder environments of northern Europe, whereasH. betaewas preferentially distributed in the warm environments of southern Europe. It was previously established thatH. betaeonly recently appeared in The Netherlands, which are in the north of Europe. Thus, our results do not support this hypothesis. Overall, this study accurately documents the geographical occurrence of two nematode crop pest species in the wild and helps identify the main environmental factors affecting their distribution range.