SCREENING SYSTEMIC RESISTANCEINDUCING FLUORESCENT PSEUDOMONADS FOR CONTROL OF BACTERIAL BLIGHT OF COTTON CAUSED BY XANTHOMONAS CAMPESTRIS pv MALVACEARUM
V. Fallahzadeh-Mamaghani, M. Ahmadzadeh, R. Sharifi
Iron-regulated metabolites, such as siderophores are important determinants of fluorescent pseudomonads in induction of systemic resistance (ISR) of plants. In this work, King’s medium B supplemented with 120 ppm 8-hydroxyquinoline (8-HQ) chelator was used for screening of pseudomonads from the rhizosphere of cotton with a high capacity to produce siderophores. Use of this medium resulted in isolates with a high ISR capability equal or greater than the reference strain P. aeruginosa 7NSK2. All strains except 13Q and EQ significantly decreased the percentage of infected area on leaves. Siderophore production by both the strains 35Q and 16Q, that were the fastest growing strains on KB media supplemented with 8HQ, was significantly higher than that of the reference strain 7NSK2. In hydroponic cultivation assays, ISR ability of 35Q depended on one or a complex of several iron regulated metabolite/s, as its ISR was significantly reduced in pots with iron excess. Nonetheless, ISR by 35Q was not completely abolished under iron excess suggesting a possible role for other determinants.