In this study, we carried out large-scale leaf spot symptom observation on vineyards in the Krasnodar Krai of Russia and determined their distribution. The incidence and severity of leaf spot were higher on the Euro-American grapevine hybrids (Bianka, Levokumskij, Avgustin, Moldova, Pervenets Magaracha, Dunavski lazur). A total of 433 isolates that belonged to the genus Alternaria were isolated from samples with leaf spot. Pathogenicity testing confirmed the ability of the representative isolates to cause necrosis on the grapevine. The isolates of Alternaria sp. were typed by the loci of internal transcribed spacer (ITS), glyceraldehyde-3-phosphate dehydrogenase (gapdh), Alternaria allergen a1 (Alt a1), β-tubulin (tub), and translation elongation factor (tef1). Isolates from grapevine causing leaf spot were shown to cluster with isolates of Alternaria. alternata (Fr.) Keissl. and Alternaria. arborescens E.G. Simmons species complex. Of the fungicides tested to inhibit Alternaria growth, the most effective were mixtures, such as pyrimethanil and fluopyram, cyprodinil and fludioxonil, and those that included difenoconazole. The results of the study expand our knowledge of the biodiversity of Alternaria sp. fungi and can be used to limit the spread of Alternaria leaf spot of the grapevine.

In this study, an analysis of the virome of 51 grapevines from the Don ampelographic collection named after Ya. I. Potapenko (Russia) was performed using high-throughput sequencing of total RNA. A total of 20 previously described grapevine viruses and 4 viroids were identified. The most detected were grapevine rupestris stem pitting-associated virus (98%), hop stunt viroid (98%), grapevine Pinot gris virus (96%), grapevine yellow speckle viroid 1 (94%), and grapevine fleck virus (GFkV, 80%). Among the economically significant viruses, the most present were grapevine leafroll-associated virus 3 (37%), grapevine virus A (24%), and grapevine leafroll-associated virus 1 (16%). For the first time in Russia, a grapevine-associated tymo-like virus (78%) was detected. After a bioinformatics analysis, 123 complete or nearly complete viral genomes and 64 complete viroid genomes were assembled. An analysis of the phylogenetic relationships with reported global isolates was performed. We discovered and characterized the genomes of five novel grapevine viruses: bipartite dsRNA grapevine alphapartitivirus (genus Alphapartitivirus, family Partitiviridae), bipartite (+) ssRNA grapevine secovirus (genus Fabavirus, family Secoviridae) and three (+) ssRNA grapevine umbra-like viruses 2, -3, -4 (which phylogenetically occupy an intermediate position between representatives of the genus Umbravirus and umbravirus-like associated RNAs).

This study analyzed the microbiome of three varieties differing in genotype and technical purpose: Cristal, Riesling, and Avgustin, all exhibiting decline symptoms of unknown etiology. A total of 92 symptomatic and asymptomatic grapevines were analyzed using ITS and 16S rRNA amplicon sequencing and molecular genetic methods. Phytoplasmas and the pathogenic bacteria Xylella fastidiosa and Xylophilus ampelinus were not present in the samples. The decline symptoms were associated with a cocktail of fungal pathogens that cause grapevine trunk diseases. In particular, the analysis revealed the causative agents of Botryosphaeria dieback (Sphaeropsis spp. and Botryosphaeria spp.), fungi associated with the Esca complex (Phaeomoniella spp., Phaeoacremonium spp., Inonotus spp., Seimatosporium spp., Stereum spp., and Cadophora spp.), and the causative agents of Phomopsis dieback (Diaporthe spp.). The symptoms of decline may be increased by several facultative grapevine pathogens that have been identified in microbiome (genera Stemphylium, Alternaria, Aspergillus, Penicillium, Talaromyces, and Fusarium). The metagenomic data of the grapevine microbiome provides opportunities for developing disease control strategies, which is important for the sustainable management of vineyards.

Ampelographic collections play an important role in the conservation of grapevine genetic resources and therefore require continuous phytosanitary monitoring. In this study, the virome of grapevines from the Magarach ampelographic collection in Russia was analyzed using total RNA high-throughput sequencing. A total of twenty-seven grapevine viruses and four viroids were identified. Two viruses were characterized as putative novel species: (+) ssRNA grapevine umbra-like virus 5 (GULV-5) and the bipartite (+) ssRNA grapevine Magarach secovirus (GMSV), which, together with related viruses, may represent a novel genus within the family Secoviridae. Among the economically important viruses, the most prevalent were grapevine fanleaf virus (76%), grapevine leafroll-associated virus 1 (39%), and grapevine virus A (33%). Mixed infections involving two or three of these viruses were detected in 50% of the analyzed grapevines. Grapevine virus D was detected in Russia for the first time. Phylogenetic analysis of 222 assembled virus and viroid genome sequences revealed high genetic diversity. The obtained results were summarized and compared with previous virome studies conducted on four Russian ampelographic collections.