Molecular epidemiology of the disease causing agent Phytophthora x cambivora as a co-dominant factor of beech trees decline in European forests

• Applicant: Dr. Tetyana Tsykun
• Subject Area: Evolution and Systematics of Plants and Fungi
• Term: since 2019
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 420020032

European beech (Fagus sylvatica) is an important late successional tree species that is native and widespread in Europe. Their decline might have severe short- and long-term ecological and economic consequences. Results of the initial project entitled with "The role of the soil genepool as a recruitment source of Phytophthora plurivora genotypes virulent to beech trees" supported by the DFG confirmed that the disease of European beech is caused mainly by two Phytophthora species, P. plurivora and P. x cambivora. The study of Phytophthora spp. Diversity in soil and in symptomatic tree tissue in beech-dominated forests across European temperate forests showed that P. plurivora was the most frequent recovered species followed by co-dominant P. x cambivora. Novel, high-quality genomes of P. plurivora assembled to a chromosome level and published during the initial project provided a keystone information for further genomic comparison between populations retrieved from the environment (soil and water) and populations causing disease and lesion of tree tissue. The results of a range of genome-wide statistical tests allowed defining the genomic regions of the P. plurivora putatively involved in elevated virulence of genotypes causing the disease. Thereby, the outcomes of the initial project confirmed ist rationale and hypothesis, and achieved ist main objective. In the renewal project, I target genomic pattern in P. x cambivora genotypes that are pathogenic towards European beech. I aim to investigate the molecular epidemiology in the pathosystem P. x cambivora - Fagus sylvatica and test the hypothesis that virulent genotypes are recruited from a diverse genetic pool that inhabited soil microbiome, and that those virulent genotypes have genomic regions involved in elevated pathogenicity similar as was discovered for P. plurivora. Next three main objectives are proposed for that: (1) completion of chromosome level assembly and annotation of the likely polyploid genome of P. x cambivora species; (2) expansion of the existing isolate collection and assess the population genomic diversity of P. x cambivora in soil and tree tissue; (3) conducting genome-wide association study to determine whether the epidemiological process of soil-borne Phytophthora spp. Becoming aggressive pathogens in forests follows a common genetic pattern across species or if it is specific to a particular species. A better understanding of the genomic underlying aspects of the emergence of aggressive genotypes has also a critical importance for the risk assessment and management of expected future epidemics of soil-borne Phytophthora species.

• DFG Programme: Research Grants