Taxonomic and phylogenetic study of rust fungi forming aecia on Berberis spp. in Sweden

Abstract: Rust fungi are important plant pathogens that have been studied for a long time. They are of great economic importance due to the severe damage they cause on agricultural crops. Rust fungi are very interesting organisms in terms of biology because their life cycle is quite complex: it alternates between two hosts and consists of up to five distinct spore stages. This makes these organisms difficult to study. The barberry plant was known to be associated with cereal rusts from the Middle Ages but only recently these plants were identified as an alternative hosts for stripe rust of important cereal crops and grasses Puccinia striiformis (Jin et al. 2010). Since 1994 barberry eradication is no longer taking place in Sweden so these plants can be found around the country. The aecial stage in the rust fungi life cycles have got less attention because it is not economically important compared with uredinial and telial stages that have been studied a lot for the species infecting cereal crops. That is why the main objective of this study was to identify aecia of rusts species that may be found on Berberis spp. collected in different parts of Sweden. To answer this question spore measurement and aecia description as well as DNA sequences analysis (using ITS region, EF1-α and β-tubulin partial genes) were performed. Also phylogenetic analysis of obtained sequences was conducted.According to spore and aecia morphology four different species were distinguished. DNA sequences analysis (by the comparison of obtained sequences with BLAST library) identified four different species P. graminis f.sp. avenae, P. graminis f.sp. tritici, P. poae-nemoralis and P. striiformis that fitted well to the morphology data. The identity of the Berberis spp. was also checked. Phylogenetic analysis showed that all obtained species and formae speciales are distinct from each other and form separate clades with high branch support.