Characterisation of Fusarium oxysporum f. sp. radicis-lycopersici in Infected Tomatoes in Inner Mongolia, China

Fusarium crown and root rot (FCRR), caused by <i>Fusarium oxysporum</i> f. sp. <i>radicis-lycopersici</i> (FORL), is an economically important disease that affects tomatoes worldwide and has become more prevalent in China in recent years. In 2021 and 2022, tomato plants in greenhouses in Hohhot, Inner Mongolia, were observed showing symptoms of stunting, premature loss of lower leaves, and root rot. Fungal pathogens were isolated from 20 infected tomato plants and identified based on morphological observation and DNA sequencing. Twelve isolates were consistently identified as <i>Fusarium oxysporum</i> f. sp. <i>radicis</i>-<i>lycopersici</i> (FORL) via an analysis of the <i>ITS</i>, TEF-<i>1α</i>, and <i>pgx4</i> genes. This is the first report of FORL in Inner Mongolia, China. The isolates were examined for their pathogenicity by inoculating them on tomatoes, eggplants, peppers, and chickpeas. The fungicide sensitivity of the isolates was determined. Effective concentrations for 50% growth inhibition (EC₅₀) were measured using seven fungicides. The EC₅₀ values of tebuconazole and prochloraz were <1.0 μg·mL^-1, exhibiting the most effective inhibition among the fungicides tested. Additionally, FORL resistance screening of tomato germplasms was performed. One tomato variety was resistant to FORL, and the remaining 43 germplasm lines showed various levels of resistance. The rates of highly susceptible, moderately susceptible, susceptible, and moderately resistant germplasms accounted for 29.55%, 22.73%, 40.91%, and 4.55% of the 44 germplasms tested, respectively.