Phytophthora alni sp. nov. and its variants described as causal agents of a new disease of alder in Europe
In 1993, a new root disease of alders (Alnus spp.) causing tree mortality was reported by the United Kingdom. The disease (formerly on the EPPO Alert List – EPPO RS 99/134) was then found in: Austria, Belgium, France, Germany, Hungary, Netherlands and Sweden. Studies have shown that the alder Phytophthora comprised a group of hybrids, probably between P. cambivora and a species related to P. fragariae. These hybrids included a common ‘standard’ type occurring across much of Europe (from Scotland and Sweden to Hungary and south east France), and four other variant types (Swedish, Dutch, German and UK variants) showing some morphological and genetic differences. Whatever the precise origins of this new alder Phytophthora are, the pathogen is now considered as a behaviourally, morphologically and genetically unique entity, which is now well established and ecologically successful in several European countries. It is therefore considered as a species unit and the name Phytophthora alni Brasier & S.A. Kirk, sp. nov. is proposed. The standard hybrid type is now formally designated as Phytophthora alni subsp. alni. The Swedish variant is designated as P. alni subsp. uniformis, and the Dutch, German and UK variants collectively as P. alni subsp. multiformis.
Brasier CM, Kirk SA, Delcan J, Cooke DEL, Jung T, Man in’t Vled WA (2004) Phytophthora alni sp. nov. and its variants: designation of emerging heteroploid hybrid pathogens spreading on Alnus trees.
Mycological Research, 108(10), 1172-1184.