Some root colonizing bacteria have been found to have beneficial effects on plant growth, and have thus been dubbed plant growth promoting rhizobacteria (PGPR). Now Indian researchers have grown pigeonpea with and without a couple of different strains of PGPR, and also with and without rhizobium infection, and have then infected the plants with the fungus that causes wilt. ((S. Dutta, A.K. Mishra and B.S. Dileep Kumar. Induction of systemic resistance against fusarial wilt in pigeon pea through interaction of plant growth promoting rhizobacteria and rhizobia. Soil Biology and Biochemistry, In Press, Uncorrected Proof, Available online 11 October 2007))
It turns out that pigeonpea plants infected with either PGPR or rhizobium developed “induced systemic resistance” to the fungus. But the resistance was actually best when both were present. I found this pretty amazing, but actually some googling reveals that it’s not that weird. It may have something to do with the increased levels of phenols in the leaves of bacterized plants. Or the reduced production of fusaric acid by the pathogen. In any case, “the results promise the combined use of PGPR and rhizobia for induction of systemic resistance against fusarial wilt in pigeon pea.” They are also another pretty amazing example of the interactions among agrobiodiversity.
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