Induction of systemic resistance by plant growth promoting rhizobacteria against red rot disease in sugarcane

Abstract

Plant growth promoting rhizobacteria (PGPR) belonging to fluorescent pseudomonads group were isolated from sugarcane rhizosphere. Selected strains were studied for the induced systemic resistance (ISR) againstColletotrichum falcatum Went causing red rot disease in the sugarcane stalks by three different resistance evaluation methods. The talc based formulations of the PGPR strains were prepared and applied through different methods and in different growth phases of the crop in the field. The pathogen was inoculated artificially later in the upper internodes and ISR was assessed. All the tested PGPR strains have significantly reduced the disease development in the stalks. ISR effect was more pronounced when the resistance was evaluated by nodal method of testing. In another trial the PGPR strains were applied to the basal stalk region in the marcotting mixture. When the pathogen was inoculated later on the upper internodes, disease development was significantly reduced in the PGPR treated canes as compared to the untreated controls. The induced resistance was maintained upto 90 days in the host after the PGPR treatment. In all these studies disease development was contained in a highly susceptible sugarcane cultivar CoC 671. When the pathogen load in the diseased canes was assessed by ELISA it was found that the PGPR treated canes recorded low titer than the control treatments. Biochemical studies indicated enhanced levels in the defense related enzymes like chitinase and peroxidase in the treated cane tissues. The pathogen inoculation resulted in lower brix, purity and commercial cane sugar percent in the PGPR untreated canes compared to the PGPR treated ones. Moreover acid and neutral invertase levels were significantly higher in the former than the latter. The induced resistance in sugarcane especially in a highly susceptible variety offers a possible alternative approach to tackle the disease under field situations and to enhance sugarcane yield.