Identification, Culture, and Fungicide Toxicity of Root Rot Pathogens Infecting Glutinous Yams

Objective Pathogens that cause root rot on Shaxian glutinous yams were identified, and their culture and effective fungicides were investigated.

Method Diseased yam samples were collected to isolate and purify the pathogens by tissue separation followed by species identification with Koch's postulates, morphological observation, and multi-locus phylogenetic analysis (ITS-LSU-TUB). Biological characteristics including optimal culture temperature and pH as well as in vitro toxicity of 7 fungicides were determined.

Results Two strains, SGF03 and SGF08, were isolated and identified as Fusarium solani and Colletotrichum alatae, respectively. The colony diameter of F. solani was significantly larger at 28°C and pH 7.0, and that of C. alatae, at 28°C and pH 6.0, than those under other conditions (P＜0.05). Among the tested fungicides, AITC, Fluazinam, and difenoconazole showed superior efficacy with EC₅₀ of 0.09, 1.25, and 6.27 μg·mL⁻¹, respectively, against F. solani and that of 0.08, 0.49, and 0.26 μg·mL⁻¹, respectively, against C. alatae.

Conclusion The Shaxian glutinous yam root rot disease was caused by coinfection of F. solani and C. alatae. In culture, F. solani grew optimally on medium at 28°C and pH 7.0, and C. alatae at 28°C and pH 6.0. Fungicides, AITC, Fluazinam, and difenoconazole, exhibited significant in vitro effectiveness on the pathogens.