New hypothesis on the ploidy of the hybrid species Phytopthora alni subsp. alni

Husson, Claude; Aguayo-Silva, Jaime; Revellin, Cécile; Marçais, Benoit; Frey, Pascal

New hypothesis on the ploidy of the hybrid species Phytopthora alni subsp. alni

2012

Husson, Claude | Aguayo-Silva, Jaime | Revellin, Cécile | Marçais, Benoit | Frey, Pascal

Alder decline caused by the Phytophthora alni complex is one of the most important diseases in natural ecosystems in Europe in the last 20 years. The emergence of Phytophthora alni subsp. alni (Paa), the pathogen responsible for the epidemics, is linked to an interspecific hybridization event between two parental species: Phytophthora alni subsp. multiformis (Pam) and Phytophthora alni subsp. uniformis (Pau). One of these parental species, Pau that has been isolated in several European countries and in North America, specifically in Alaska and Oregon, is exotic to Europe and a diploid species [1] [2]. Pam possesses a polyploid genome and should normally be tetraploid [2]. In this study, our aim was to determine the ploidy of the hybrid species Paa by using flow cytometry and Real‐Time PCR. Firstly, flow cytometry analysis on suspensions of zoospores allows us to compare the genome size of the three species. Secondly, we designed allele‐specific primers and probes in order to quantify the number of copy of alleles from three single copy nuclear genes by using quantitative PCR. Both results are consistent and indicate that Paa should be a triploid species.

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