Diversity of Fusarium Species Causing Storage Rot of Table Beet in the Moscow Region of the Russian Federation

Fusarium fungi are known to infect table beet (Beta vulgaris subsp. vulgaris) plants at various stages of development worldwide. Fusarium root rot, which develops post-harvest during long-term storage, is of particular economic significance. In Russia, there is no up-to-date information about the species diversity of pathogens causing this disease of table beets, which determined the purpose of this study. A total of 28 Fusarium isolates were collected from affected beet roots grown in the Moscow region of the Russian Federation from 2018 to 2023 years. Molecular phylogeny based on the TEF-1α and RPB2 genes in combination with morphological characterization showed that five Fusarium species were involved in the pathogenesis of Fusarium root rot of table beet during storage: F. acuminatum (43% of the total number of isolates), F. avenaceum, F. campestre (FTSC); F. sporotrichioides (FSAMSC) and F. solani (FSSC). At the same time, the species F. acuminatum, F. campestre, and F. sporotrichioides were first discovered on beet root in the Russian Federation. Temperature sensitivity of the identified species was studied at 5 °C and 25 °C. According to the value of the cold sensitivity index (CTI) on the nutrient medium and native substrate, the isolates were distributed differently: F. campestre (0.32) > F. acuminatum (0.22) > F. avenaceum (0.21) > F. sporotrichioides (0.19) > F. solani (0.20) and F. acuminatum (0.32) > F. campestre (0.21) > F. solani (0.03) > F. avenaceum and F. sporotrichioides (0.01), respectively. This confirms the need to study the pathogenic properties of isolates on a natural substrate (host plant) under different temperature conditions. When infected with the dominant and most aggressive species F. acuminatum, there was a high variation in the size of the affected area, depending on the genotype of the lines, under both temperature conditions (Va = 2–8 mm3 at 5 °C and Va = 31–1760 mm3 at 25 °C). Therefore, this species can be considered to be the most objective differentiating factor in assessing the resistance of table beet roots to fusarium rot, which determines the need to include it in the breeding process for creating resistant varieties and hybrids for the Central region of Russia. The data obtained in this study are of great importance for developing strategies for managing Fusarium fungi associated with Fusarium rot of beet-root during storage. The research results will also be relevant for other vegetable crops that remain fresh for long periods of time or undergo vernalization in the case of seed production at low temperatures.