Identification and growth characteristics determination of sweet potato foot rot pathogens

【Objective】To isolate and identify the pathogen of sweet potato foot rot disease in Ninghai County, Zhejiang Province, and to realize the biological characteristics of the pathogen, so as to provide theoretical guidance for the prevention and control of sweet potato foot rot disease in field.【Method】Pathogen of sweet potato foot rot collected from Ninghai, Zhejiang Provence was isolated through tissue isolation method and it was verified according to Koch's rule. And the species of pathogen was identified by the morphological and molecular biological method. To confirm the biological characteristics of pathogen, the growth of pathogen in different mediums, temperature, pH, carbon and nitrogen sources were measured using mycelium cultivation method.【Result】One strain of fungus was isolated and purified from sweet potato foot rot sample, marked as RF-NH. According to Koch's rule, it was verified as pathogen of sweet potato foot rot disease. DNA of strain RF-NH was amplified with general primers of ITS, His3 and Cal genes, and length of gene segments were 579, 480 and 537 bp, respectively. Phylogenetic analysis showed that strain RF-NH were clustered with Diaporthe batata. Given the results of morphological and molecular biological identification, pathogen of sweet potato foot rot disease in Ninghai, Zhejiang Provence was identified as D. batatas. Results of pathogen biological characteristic determination of D. batatas:the suitable temperature for mycelial growth of D. batatas ranged from 15 to 35℃;and the optimum temperature for growth was 25℃ suitable pH for mycelial growth ranged from 4 to 12;and the optimum pH was 4;moreover, the optimal carbon and nitrogen sources for mycelial growth were dextrin and sodium nitrate, and the optimal medium was Sweet Potato Dextrose Agar. In addition, the lethal temperature for conidium growth was 50℃ for 10 min and the lethal temperature for mycelial growth was 49℃ for 15 min or 50℃ for 10 min.【Conclusion】D. batatas is the pathogen of sweet potato rot disease in Ninghai, Zhejiang Province. The temperature range for mycelial growth of D. batatas is narrow, and 25℃ is preferable for the pathogen. The pH range is wide, and the acid environment is more suitable for its growth. The most suitable medium is SPDA medium. According to the growth characteristics of D. batatas, changing cultivation environment, adjusting soil pH, applying fertilizer scientifically and rotating crops can inhibit the growth of D. batatas, so as to realize the decrease of sweet potato foot rot disease damage.