[Pathogen identification of leaf-spot and its biological characteristics on Gentiana spp].

OBJECTIVE: To clear the pathogen of leaf-spot on (Gentiana spp. in Gansu province, and to control the disease theoretically. METHODS: The symptoms were obsersed and described in the field. The pathogen was identified on the base of morphology. The factors influencing the colony growth, myceliuim gross and sporulation were studied by the suspension and solid meedia. RESULTS: The pathogen was identified as Septoria gentionae. PDA and PSA were benefitial for colony growth and sporolation. The optimum temperature for colony growth, sporulation and mycelium gross were 25 degrees C. 20 degrees C and 20 degrees C respectively. The optimum pH was 7 for the pathogen growing and sporulation. 12h light plus l2 h dark, 8 hours UV plus 16 h light were beneficial to colony growing and sporulation. All-dark, 8 hours UV plus 16 hours dark were good for mycelium gross. Among 11 carbon sources, xylose, sucrose and soluble starch were very good for colony growth. Sucrose was best for sporulation, while raffilose best for mycelium gross. Among nitrogen sources, colony growth and sporulation quality reached highest on alanine, urea and NANO2 were not utilized very well. NH4H2PO4 was the best for sporulation and mycelium gross.