We report here the annotated genome sequence of Xanthomonas arboricola strain 3004, isolated from barley leaves with symptoms of streak and capable of infecting other plant species. We sequenced the genome of X. arboricola strain 3004 to improve the understanding of molecular mechanisms of the pathogenesis and evolution of the genus Xanthomonas.

The Volga region is one of the main grain-producing regions of Russia. Wheat stem rust caused by Puccinia graminis f. sp. tritici is among the most destructive fungal diseases of wheat. Recently, its harmfulness has increased in the Volga region. In this regard, an analysis of the resistance and diversity of the Sr genes in the Russian wheat cultivars is necessary. In this work, 126 wheat cultivars (including 23 durum wheat cultivars and 103 bread wheat cultivars) approved for use in the Volga region were evaluated for their resistance to two samples of P. graminis f. sp. tritici populations from different Volga region areas at the seedling stage. Specific DNA primers were used to identify resistance genes (Sr2, Sr24, Sr25, Sr26, Sr28, Sr31, Sr32, Sr36, Sr38, Sr39, and Sr57). Highly resistant cultivars (30 from 126) were identified. In bread wheat cultivars, the genes Sr31 (in 19 cultivars), Sr24 (in one cultivar), Sr25 (in 15 spring wheat cultivars), Sr28 (in six cultivars), Sr38 (in two cultivars), and Sr57 (in 15 cultivars) and their combinations—Sr31 + Sr25, Sr31 + Sr38, Sr31 + Sr28, Sr31 + Sr57, Sr31 + Sr28 + Sr57, and Sr31 + Sr24—were identified. The obtained results may be used to develop strategies for breeding rust-resistant cultivars.

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Global climate warming and involvement of new regions with endemic populations of microorganisms in commercial seed production have led to an increase in the diversity of phytopathogenic bacteria that are affecting major crops, including the fruit trees. As a rule, emergence of new pathogens is associated with importation of infected seeds and planting material, cultivation of new species and varieties of plants, and expansion of agricultural trade with foreign countries. One of the leaders in diversity among phytopathogens is the genus Xanthomonas bacteria, affecting more than 400 plant species. Among the characteristic signs of xanthomonads is the high frequency of horizontal gene transfer both within the genus and between phylogenetically removed bacterial taxa – up to 25% of the genes are of this origin. In this paper, we consider another source of increasing the number of phytopathogenic species – by the epiphytic populations. These bacteria are the likely ancestral form of the phytopathogenic bacteria of the genus Xanthomonas.

Potato spindle tuber viroid (PSTVd) is a harmful quarantine disease with wide geographic distribution. To date, experimentally proved resistance or tolerance of potato cultivars to PSTVd has not been reported. The aim of this study was to evaluate responses to four PSTVd strains of 39 modern potato cultivars of different origin. Four PSTVd strains of different origin, the intermediate VP35, VP87, and two sever strains FP10-13 and NicTr-3, deposited in GenBank, were used. Transcripts of these strains were used to inoculate tomato plants of the cv. Rutgers. Before PSTVd inoculation with tomato sap, all plants were tested for viral infection by ELISA. The presence of PSTVd in infected plants was verified by RT-PCR as well as by RT-qPCR at sixty days post-inoculation (dpi). The strain-specificity in the response of cultivars to viroid infection was revealed. Five cultivars were identified in which, after the first inoculation of plants with all PSTVd strains, normal in shape tubers were formed. All plants of the next generation derived from infected but normally shaped tubers showed strong symptoms of disease. PSTVd and mixed viroid/viral infection (PVY + PSTVd, PVM + PSTVd, and PVY + PVS + PSTVd) led to a significant decrease in the number and weight of tubers in most of the cultivars studied.