| Abstrakt: |
In order to obtain chickpea (Cicer arietinumL.) rhizosphere-competent bacteria, 256 bacterial strains, representing different morphological types, were screened for their biocontrol activity against Fusarium oxysporumf.sp. ciceri, Rhizoctonia bataticolaand Pythiumsp. under in vitro conditions. Pseudomonassp. NBRI9926 and Rhizobiumsp. NBRI9513 were selected for further work because of their unique ability to inhibit all three fungi. Spontaneous rifampicin-resistant (Rifr) derivatives of Pseudomonassp. NBRI9926 and Rhizobiumsp. NBRI9513 showing a growth rate and membrane protein composition comparable to the wild-type were selected to elucidate their rhizosphere competence on chickpea. Both strains showed no difference to their corresponding wild-type strains in terms of chickpea rhizosphere competence. However, when Pseudomonassp. NBRI9926P3 was mixed in an equal or lower ratio with Rhizobiumsp. NBRI9513R7, both in sterile soil and non-sterile soil assays, Rhizobiumsp. NBRI9513R7 consistently failed to achieve titres similar to Pseudomonassp. NBRI9926P3. These results suggest that antibiotic resistance-marked strains should be compared with wild-type parents before being used as monitors of parental strain survival. Pseudomonassp. NBRI9926P3 was a better chickpea rhizosphere coloniser compared to Rhizobiumsp. NBRI9513R7. Greenhouse results demonstrated a superior biocontrol potential of Pseudomonassp. NBRI9926P3 to control F.oxysporumf.sp. ciceri, R. bataticolaand Pythiumsp. compared to Rhizobiumsp. NBRI9513R7. The screening method should prove useful in identifying rhizosphere bacteria with the greatest potential for controlling diseases caused by phytopathogenic fungi. |
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