Plasmopara elegantissimasp. nov. (Oomycota, Peronosporales), a Downy Mildew Species Specialized toImpatiens textori(Balsaminaceae)

Abstract

Over the past 15 years, downy mildew became the most destructive foliar disease in cultivatedImpatiensspecies (Balsaminaceae) worldwide. A previous study had revealed that the causal agent was notPlasmopara obducens(Oomycota, Peronosporales) butPlasmopara destructoronImpatiens walleriana, andPlasmopara velutinaonImpatiens balsamina. This hints to a relatively high degree of specialization ofPlasmoparaon Balsaminaceae. Therefore, it was the aim of the present study to perform multigene phylogenetic analysis and detailed morphological investigation for several Korean downy mildew samples parasitic to cultivatedI. walleriana, andI. balsamina, but also to a northeast Asian wild plant,Impatiens textori. It was revealed thatI. textoriharbors a new species, which is introduced and described here asPlasmopara elegantissima.