Identification of Pathogen and Biocontrol Agents on Southern Blight of Pseudostellaria heterophylla

  Objective  Pathogen and potential biocontrol agents of the southern blight, a major soil-borne disease, of Pseudostellaria heterophylla were identified.

  Method  P. heterophylla plant parts and tubers showing the typical southern blight symptoms were collected for the pathogen isolation. The isolate was examined by morphological, molecular biological, and pathogenicity tests for taxonomic confirmation. Microbes with an antibacterial property against the isolate were screened using the plate confrontation culture method to evaluate the potential of their being used as a biocontrol agent on the blight.

  Result  On culture plate, the round colonies of the suspected pathogen had white, silky, spreading mycelia with septa and ramifications that, at later stage, formed sclerotia in different colors. The isolate was further identified as Athelia rolfsii by ITS, LSU, and TEF-1α gene sequence analyses. The disease symptoms on the plants inoculated with the isolate were identical to those observed in the field and in accordance with Koch's rule. On the biocontrol efficacy evaluation, Bacillus velezensis FJAT-17931 and B. siamensis FJAT-52595 displayed high inhibitory effect against A. rolfsii with the rates of 72.23 % and 71.16%, respectively.

  Conclusion  The pathogen of the southern blight on P. heterophylla was identified as A. rolfsii. Two Bacillus strains were found to be potentially applicable as biocontrol agents on the disease that can cause serious yield loss on the crop.