Molecular Identification, Effector genes and Virulence of Isolates of <i>Parastagonospora nodorum</i> from Altai Krai (Russia)

Abstract

Septoria blotches represent some of the most harmful wheat diseases that encompass all grain-producing countries worldwide. They are caused mainly by fungi of the genera Parastagonospora and Zymoseptoria. The aims of the research were to analyze the nucleotide sequences of two phylogenetically informative DNA loci, ITS and tub2, of Parastagonospora nodorum isolates from the Altai Krai, to detect the presence of Tox1, Tox3, ToxA effector genes and to study the virulence of the isolates. Microscopic analysis of fragments of affected plant tissue was used for primary identification of the Septoria blotch. The causative agent from the studied plant samples was identified as P. nodorum. Fungal colonies cultivated on potato-glucose agar displayed a well-developed light brown velvety mycelium with dark periphery (mixed type) and numerous pycnidia exhibiting high sporulation capacity. Microbiological diagnostics were complemented by molecular genetic studies. Sequencing of ITS and tub2 loci isolates revealed complete genetic identity of all eight studied monoconidial isolates obtained from different samples. PCR-based detection of tree Tox-genes demonstrated that the only Tox3 was present in the geno-types of 80 tested P. nodorum monoconidial isolates. The ToxA and Tox1 genes were not found in the studied isolates. The virulence of P. nodorum isolates was evaluated in laboratory conditions using an isolated wheat leaves assay. Mixture of four isolates from spring wheat and one isolate from winter wheat, were characterized as virulent. When spring and winter wheat cultivars were infected with two isolates obtained from oats, pathogenic but avirulent properties were detected. The isolate from triticale was avirulent to winter wheat cultivars and virulent to spring wheat cultivars.