study of interaction between mycorrhiza glomus fasciculatum and pseudomonas fluorescens on control of common root rot of wheat caused by bipolaris sorokiniana

the common root rot of wheat caused by bipolaris sorokiniana is considered as an important disease of world wide distribution including iran. biological control of b. sorokiniana can be an effective method for control of this disease. for this purpose, the biocontrol potential of mycorrhiza glomus fasciculatum, pseudomonas fluorescens sh4 and a mixture of the two was evaluated for the common root rot in greenhouse condition(22-25oc). 7 wheat seeds variety chamran were sown in 200 ml polyethylene pots. half of them were inoculated by g. fasciculatum and another half remained uninoculated. they were irrigated by hogland's nutritient solution. thirty five days later the plantlets were transferred to the polyethylene pots containing one kg. autoclaved soil. depending on the different treatments, the pots were inoculated or not, with causal agent of disease b. sorokiniana, p. fluorescens or mixture of two,. experiment was arranged as a factorial test using completely randomized design with 8 treatments and 4 replications. the plants were irrigated normally and harvested 5 weeks after transplanting of the plantlets. the roots were washed with care, and noted for disease index on the roots and fresh weights of roots and shoots were recorded. the results showed that the presence of mycorrhiza, pseudomonas and the mixture of them around and on the roots of plants, inoculated by b. sorokiniana, decreased significantly the severity of disease at the rate of 43, 50.75 and 78.75 % respectively in comparison with controls (no mycorrhiza and no pseudomonas. comparable results were noted for the fresh weight of roots and aerial parts of plants in the same treatments. it could be concluded that application of mycorrhiza g. fasciculatum, p. fluorescens and a mixture of the two on wheat decrease not only the severity of disease caused by b. sorokiniana but also increases the weights of both bipolaris infected and non infected plant. this increase in yield was significantly higher in the treatments inoculated with the mixture of mycorrhiza and pseudomonas as compared to the treatments inoculated with only one of each biocontrol agent.