Identification of Phytophthora alni subspecies in riparian stands in the Czech Republic

Abstract

In the Czech Republic, Phytophthora alni was first confirmed in 2001 and the pathogen has been quickly spreading and occupying almost the whole area of the country. The pathogen attacks Alnus glutinosa or A. incana to a lesser extent and causes considerable losses of alder trees along hundreds of kilometres of riverbanks. The aim of our work was to perform the identification of P. alni isolates at the subspecific level using PCR and to determine the frequencies and distribution of particular subspecies. The allele-specific PCR primers focused on allele diversity of orthologs of ASF-like, TRP1, RAS-Ypt, and GPA1 genes were selected for identification. Eighty-eight per cent of the 59 analysed isolates belonged to P. alni ssp. alni while 12% were P. alni ssp. uniformis. P. alni ssp. multiformis has not been recorded in the country till now. The two subspecies differed in distribution. P. alni ssp. alni dominated in riparian stands along broader rivers in lowlands and the results confirmed the more effective spreading of P. alni ssp. alni based on its higher aggressiveness and ecological advantage. P. alni ssp. uniformis was acquired rather from riparian stands of small watercourses at higher altitudes. The insular distribution of P. alni ssp. uniformis may represent the remains of its former occurrence. Therefore, P. alni ssp. uniformis may be an indigenous subspecies suppressed by the more aggressive related taxon.