Identification and Pathogenicity of IFusarium/I Species Associated with Onion Basal Rot in the Moscow Region of Russian Federation

Fusarium basal rot of onions causes large losses during storage of commercial production of onion bulbs, which in turn adversely affects the food market situation in the off-season period. There are no data on the composition of Fusarium spp., which causes onion basal rot in the Russian Federation. Therefore, our research was aimed at Fusarium spp. causing onion basal rot in the Moscow Region of the Russian Federation and studying the pathogenicity of these species for the host plant. We studied 20 isolates of Fusarium spp. collected from affected mature bulbs and seed bulbs. Species identification of the isolates was carried out using analysis of the nucleotide sequences of the three genetic loci ITS, tef1 and rpb2, as well as was based on the macro- and micromorphological characteristics of these isolates. As a result, the species F. annulatum (F. fujikuroi species complex), F. oxysporum (F. oxysporum species complex), F. acuminatum (F. tricinctum species complex) and F. solani (F. solani species complex) were identified to involve in the pathogenesis of Fusarium basal rot. We have shown for the first time that the species F. annulatum and F. acuminatum are highly aggressive and capable of causing onion basal rot. The predominant species were F. annulatum and F. oxysporum. The proportion of these species in the total number of analyzed isolates was 60% and 25%, respectively. The largest proportion (33%) of highly aggressive on mature bulbs isolates was found in the species F. annulatum. The data obtained provide practical insights for developing strategies to manage Fusarium fungi responsible for onion basal rot Moscow Region of the Russian Federation. In addition, data about species composition and aggressive isolates may be used in onion breeding for resistance to Fusarium basal rot.