Spatial distribution and basic ecology of Heterodera schachtii and H . betae wild populations developing on sea beet, Beta vulgaris ssp. maritima
Résumé
Most populations of crop pathogens have wild relative populations from which they can originate but for which basic knowledge of their ecological requirements in natura is 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 on Heterodera schachtii and H. betae, two cyst nematodes that cause severe damage to sugar beet (Beta vulgaris ssp. vulgaris) crops and can develop on a wild beet relative, the sea beet (B. vulgaris ssp. 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 host B. v. ssp. maritima along the European Atlantic and North Sea coastlines. Results showed that H. schachtii mainly occurred in the colder environments of northern Europe, whereas H. betae was preferentially distributed in the warm environments of southern Europe. It was previously established that H. betae only 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.