Identification and biological characteristics of Colletotrichum americae-borealis causing alfalfa anthracnose in Heilongjiang

In August 2019, a disease survey was conducted on the 2nd-age cultivated alfalfa (Medicago sativa) in Minzhu Township, Daowai District, Heilongjiang Province. Symptoms appeared oval or irregular, small black spotson the surface of the alfalfa stalks. This disease can seriously damage phoem tissue. This study identified the pathogen and the biological characteristics of the pathogen. According to both morphological characteristics, analysis of multiple loci, and pathogenicity test, the pathogen was identified as Colletotrichum americae-borealis. Studies on the biological characteristics of pathogen showed that the optimal medium, nitrogen source and carbon source for mycelial growth of C. americae-borealis were PDA, peptone, soluble starch and sucrose, with 1.02, 0.91 and 0.82 cm·d^–1, respectively; the optimum sporulation conditions were PDA, peptone and glucose, with 1.3 × 10⁶, 1.8 × 10⁵ and 3.6 × 10⁶ spore·mL^–1, respectively.