Isolation and evaluation of bacterial endophytes against Sclerospora graminicola (Sacc.) Schroet, the causal of pearl millet downy mildew

Pooja Sangwan,Leela Wati,Kushal Raj,Anil Kumar

doi:10.1186/s41938-021-00468-5

Abstract

BackgroundPearl millet remains prone to many diseases; among them downy mildew caused by Sclerospora graminicola (Sacc.) Schroet is economically more important. The use of endophytic bacteria for management of downy mildew of pearl millet as eco-friendly approach is increasing attention as sustainable alternative to pesticides. The objective of the present study was to isolate endophytic bacteria from roots of pearl millet cultivars and assess for biocontrol activity against Sclerospora graminicola.ResultsThirty pearl millet root bacterial endophytes (PMRBEs) were isolated and screened in vitro for biocontrol activities such as: siderophore production, hydrogen cyanide (HCN) production and 1-amino cyclopropane-1-carboxylate (ACC) deaminase activity. Sixteen isolates possessed siderophore production potential, 3 isolates were found to be HCN producers, and 30% of the bacterial endophytes showed a good growth on ACC supplemented plates. On the basis of biocontrol activities, promising endophyte PMRBE6 was selected for seed treatment as well as a foliar spray to manage downy mildew of pearl millet in screen house experiment. The isolate PMRBE6 was found to be effective in managing downy mildew disease. Grain yield, test weight, plant height and average number of productive tillers were found to be maximum on inoculation of seeds of different pearl millet cultivars with PMRBE6, and the results were statistically significant as compared to control.ConclusionsOn the basis of biochemical characterization and partial 16S rRNA sequencing, the isolate PMRBE6 was identified as Bacillus subtilis strain PD4 (Accession no. MN400209). Pearl millet root bacterial endophyte (PMRBE6) exhibiting biocontrol activities could be exploited in friendly, sustainable organic agriculture.

Highlights

Pearl millet remains prone to many diseases; among them downy mildew caused by Sclerospora graminicola (Sacc.) Schroet is economically more important
Isolation of pearl millet root bacterial endophytes and their evaluation for biocontrol activities A total of 30 pearl millet root bacterial endophytes of various morphology (PMRBE1-PMRBE30) were retrieved from roots of pearl millet raised during the fall of 2016 and 2017
All endophytic bacterial isolates were screened for biocontrol activity by assessing their ability for siderophore production, hydrogen cyanide (HCN) production and amino cyclopropane-1-carboxylate (ACC) utilization

Summary

Introduction

Pearl millet remains prone to many diseases; among them downy mildew caused by Sclerospora graminicola (Sacc.) Schroet is economically more important. The use of endophytic bacteria for management of downy mildew of pearl millet as eco-friendly approach is increasing attention as sustainable alternative to pesticides. The use of endophytic bacteria for managing pathogenic fungi and bacteria is receiving increasing attention as sustainable alternative to pesticides, etc. Endophytic bacteria have been found virtually in every plant, where they colonize internal tissues of their host plants and can form different relationships like symbiotic, mutualistic, commensalistic and trophobiotic. They influence plant growth by producing phytohormones such as indole acetic acid, cytokinins and gibberellins (Sandhya et al 2017). In most of the plants, roots have the higher endophytic population as compared to above-ground tissues (Rosenblueth and Martínez-Romero 2004); and their population decreases progressively from the stem to the leaves (Quadt-Hallman et al 1997)

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