Role of iron in rhizobacteria-mediated suppression of root-infecting fungi and root-knot nematodes in tomato


  • I. A. Siddiqui
  • S. S. Shaukat


The comparative efficacy of Pseudomonas aeruginosa strain 1E-6 and its streptomycin resistant strain 1E-6 S+ was assessed to cause suppression against root-infecting fungi including Macrophomina phaseolina, Fusarium solam' and Rhizoctonia solani and the root-knot nematode Meloidogyne javanica in tomato. 1E-6 and 1E-6S+ markedly suppressed nematode population densities in root and subsequent root-knot development. Strain 1E-6S+ significantly suppressed K solani infection. Both the bacteria failed to suppress M. phaseolina and F. solani. Whereas bacterial populations declined in the rhizosphere and inner root tissues of tomato, the colonization pattern of the two bacteria was identical. When iron concentration in the soil was lowered by the addition of an iron chelator, suppression of F. salam' and K salam' by strains 1E-6 and 1E-6S+ was substantially increased. However, against M. phaseolina and M. javanica, efficacy of the two strains was uninfluenced by the addition of the iron chelator.