Abstract
The present study was designed to compare the defense response of the host plant towards endophytic bacteria Pseudomonas aeruginosa PM389 and pathogenic bacteria Erwinia carotovora and to correlate the level of defense enzymes vis-a-vis bacterial colonization in the host. Wheat seedlings were treated with 107-108 cells ml-1 endophytic and pathogenic bacteria in the separate experimental set-up, and the level of plant defense enzyme was measured at various time intervals. Comparatively reduced level of most defense enzymes was produced in endophytic bacteria treated plants. While the endophytic bacterial population was almost constant after 24 HAI (hour after inoculation), the population of pathogenic bacteria kept fluctuating during the study period from 24 HAI. Unlike pathogenic bacteria, we observed attenuated defense response in challenged host plants towards endophytic bacteria, which helps endophytes establish inside plant. This study would be useful for understanding the mechanism of colonization and strategies of endophytes to fight against the host defense response.
Highlights
Plants harbor a diverse micro-flora of soil-borne bacteria and fungi that may have either beneficial or deleterious effects on the plant
During this period (24-48 HAI), pathogen treatment resulted in a significantly highest change in the activity of Peroxidase activity (PO) enzyme, while repressed enzyme activity was recorded in endophytic bacteria (PM389) treated plants in comparison to control treatment (Fig. 1a.)
No significant deviation in Polyphenol oxidase (PPO) activity was observed in plants treated with endophytic bacteria from the PPO activity noted in control plants (Fig. 1b.). β-glucanase
Summary
Plants harbor a diverse micro-flora of soil-borne bacteria and fungi that may have either beneficial or deleterious effects on the plant. Various studies suggest that entry of endophytes in root is facilitated through wounds, cracks, and the points of lateral root emergence.[3,4] The rhizosphere is the site of the complex interaction between plant and soil microflora, where plant exudates like organic acids, amino acids, and proteins etc., released from plants are responsible for initiating the colonization of bacterial endophytes in the plant interior.[5] Since both endophytic (beneficial) and pathogenic (harmful) bacteria are capable of colonizing the host interior, successful establishment of endophytic bacteria inside the plant depends on genotypic compatibility, physiological status, and extent of host plant defense response.[6] favored colonization of endophytes over pathogenic bacteria indicates interplay between plant and bacterial traits
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