Evaluation and Control of Stem Rot in Adzuki Bean Caused by <i>Fusarium graminearum</i> and <i>F. oxysporum</i> in Northeast China

Adzuki bean [<i>Vigna angularis</i> (Willd.) Ohwi & H. Ohashi] is a high-value legume crop widely cultivated globally, primarily in Asia, for its nutritional benefits and economic importance. In 2023, an epidemic outbreak of stem rot disease was observed in commercial adzuki bean fields in Shangzhi City, Heilongjiang Province, China. Through tissue isolation and fulfillment of Koch's postulates, nine pathogenic fungal isolates were obtained from diseased stems. Morphological, molecular, and phylogenetic analyses identified <i>Fusarium graminearum</i> Schwabe and <i>F. oxysporum</i> f. sp. <i>glycines</i> as the causal agents, representing the first report of these fungi causing stem rot on adzuki bean in China. Pathogenicity testing of nine plant species (seven legumes and two cereals: corn and wheat) revealed that all tested crops commonly cultivated in Northeast China were susceptible to infection by <i>F. graminearum</i> and <i>F. oxysporum</i>. In vitro screening identified high sensitivity of <i>F. graminearum</i> to tebuconazole, with 80.0% mycelial growth inhibition at 4.3 × 10⁻⁴ g·mL⁻¹, and high sensitivity of <i>F. oxysporum</i> to ethylicin, with 82.7% inhibition at 8.0 × 10⁻⁴ g·mL⁻¹. This study provides a comprehensive characterization of the pathogens, defines their host range, and identifies tebuconazole and ethylicin as effective candidates for field control, offering management strategies to protect adzuki bean production in Heilongjiang Province.