The Effects of Bacillus pumilus, Isolated from Wheat Rhizosphere, on Resistance in Wheat Seedling Roots against the Take-all Fungus, Gaeumannomyces graminis var. tritici

The aim of this study was to verify that induced resistance was another mechanism through which Bacillus pumilus 7 km can suppress Gaeumannomyces graminis (Sacc.) Von Arx and Oliver var. tritici Walker (Ggt). Also, plant growth-promotion activity of B. pumilus 7 km and its effect on disease severity of take-all were evaluated. Soil was drenched with B. pumilus 7 km and disease severity, root and shoot fresh weights and root and shoot heights were evaluated. The activities of soluble peroxidase (SPOX), ionically cell wall-bound peroxidase (CWPOX), b-1,3-glucanase, b-1,4-glucanase and the contents of total phenolic compounds were also determined. The results indicated that disease severity in the bacterized roots was significantly less than the pathogen control roots. Also this isolate promoted root height, root and shoot fresh weights, compared with the healthy control plants. Wheat plants treated with B. pumilus 7 km showed increased presence of SPOX, CWPOX, b-1,3-glucanase, b-1,4- glucanase and phenolic compounds in bacterized roots challenged with the pathogen. In this treatment, maximum SPOX, b-1,3-glucanase and b-1,4-glucanase activities on day 4 and CWPOX activity on day 8 were recorded. Also, maximum total phenolic concentration on day 6 was recorded. The results suggest that the inhibitory effect of B. pumilus 7 km on the take-all may be related to its ability to enhance defense responses in the wheat roots