Identification, Biological Characteristics, and Effective Fungicide of Pathogen Causing Leaf Spot Disease on Vicia faba in Jiangsu Province

Objective Pathogen that caused the leaf spot disease on Vicia faba in Jiangsu Province was identified, its biological characteristics studied, and effective germicide determined.

Method  Suspected pathogens of the leaf spot disease were collected by tissue isolation culture, and subsequently, identified by a pathogenicity test, morphological observations, and a phylogenetic analysis based on ITS and GAPDH sequence. Biological characteristics and sensitivity to 10 fungicides of the identified pathogen were determined.

Results  Alternaria alternata was identified as the pathogen that infected V. faba in Jiangsu. It grew optimally on a potato dextrose agar or an oatmeal agar medium containing maltose or glucose for carbon source and yeast or beef extract for nitrogen at 25 ℃ and pH 6.0-9.0 under continuous light exposure or 12h alternating light and dark conditions. Among the 10 fungicides tested, sophocarpidine and fluazinam exhibited the greatest inhibition on the growth of the isolate at EC₅₀ of 0.0220 mg·L⁻¹ and 0.6309 mg·L⁻¹, respectively.

Conclusion  The pathogen of the leaf spot disease on V. faba in Nantong, Jiangsu was identified to be A. alternata. Its biological characteristics and high in vitro toxicity by sophocarpidine and fluazinam were determined.