Effects of Pseudomonas fluorescens CHA0 on the resistance of wheat seedling roots to the take-all fungus Gaeumannomyces graminis var. tritici

The aim of this study was to verify that wheat seedlings treated with Pseudomonas fluorescens CHA0 (CHA0 hereafter) before inoculation with Gaeumannomyces graminis var. tritici (Ggt), a pathogen of take-all, acquire induced resistance to Ggt. The soil with wheat seedlings growing on it was drenched with a suspension of CHA0 cells and inoculated with Ggt 24 h later. Then, the seedlings were grown in a glasshouse, and severity of take-all disease, fresh weights of root and shoot and lengths of root and shoot,and also the activities of soluble peroxidase (SPOX), ionically cell-wall-bound peroxidase (CWPOX), beta-1,3-glucanase, beta-1,4-glucanase and the concentration of total phenolic compounds in the root of the seedlings were examined. The results indicated that the treatment with CHA0 before inoculation with Ggt mitigated the disease severity significantly, and increased the root and shoot lengths and root and shoot fresh weights. The treatment with CHA0 increased the activities of SPOX, CWPOX, beta-1-3-glucanase, beta-1,4-glucanase and phenolic compounds in the wheat roots and the activities of SPOX and beta-1,4-glucansee activities were highest at day 4 and those of CWPOX and beta-1,3-glucanase at day 6 after inoculation with Ggt. The concentration of total phenolic compounds was also highest at day 6 after the inoculation with Ggt. The results suggest that the take-all suppressing effect of CHA0 may be related to enhanced defense response of the wheat roots.