Biological Characteristics of Tobacco Target Spot Pathogens in Hubei Province

To clarify the biological characteristics of Rhizoctonia solani, the pathogen causing tobacco target spot in Hubei Province, the biological characteristics of 33 strains, including mycelial growth rate, sclerotial number, optimal growth carbon source, nitrogen source, temperature, were evaluated using the mycelial growth rate method. The host range of the pathogen was determined using the needle inoculation method. The results showed that strains of the tobacco target spot from different geographical origins in Hubei Province exhibited differences in mycelial growth rate and sclerotia production. The optimal carbon source and nitrogen source for the three different pathogenic types of strains were soluble starch and peptone, respectively. The optimal growth temperature was 25°C, and the lethal temperature for mycelia was 50°C. Host range tests indicated that the highly pathogenic strain XEMS25-1 could cause symptoms consistent with tobacco target spot on Solanum melongena var. serpentinum, Solanum lycopersicum, Cucumis melo, Cucurbita pepo, and Capsicum annuum var. longum, but could not infect Brassica campestris ssp. pekinensis, Lactuca sativa var. longifolia, Lactuca sativa, Lactuca sativa var. angustana, Cucurbita moschata, Brassica rapa subsp. chinensis, or Oryza sativa. These findings provide a theoretical basis for the green control of tobacco target spot in Hubei Province.