Species membership of the sunflower stem blight isolates collected in some fields near Krasnodar

The prevalence of a dangerous quarantine pathogen, the sunflower stem blight pathogen (Phomopsis helianthi Munt.-Cvetk. Mihaljc. & M. Petrov), varies depending on weather conditions and the reserves of its infectious matter in the soil. In 2010, it was proposed to keep the name of the pathogen Diaporthe, which was used in the literature before all potential synonyms. Currently, of the 14 species of Diaporthe that can be potential pathogens of sunflower stem blight in Russia, there have been identified species other than D. helianthi: D. phaseolorum and D. gulyae, D. monetii and D. vangoghii sp. (confirmed by molecular genetic studies). There is a possibility that these stem blight species will spread in Russia with infected seed material. We selected stem and seed samples with the affection symptoms characteristic of Diaporthe helianthi in sunflower sowings from the fields near Krasnodar to clarify the species membership of the pathogen. We identified a total of 39 isolates of the pathogen as a pure culture. We conducted the study of cultural features according to the methods of experimental mycology. Isolates of the pathogen differed in cultural characteristics, but only р-spores were formed in pycnidia, which is characteristic of Diaporthe helianthi. We carried out the identification of the species membership of 17 pathogen isolates in the sequencing department of TsKP "Biotechnology". Of these, 16 isolates were identified with 99-100 % probability as Diaporthe helianthi and one isolate as Xylaria ellisii.