Microbiological Control of Xanthomonas Induced Bacterial Leaf Streak Disease of Wheat via Phytocompounds and ROS Processing Enzymes Produced Under Biotic Stress

Common wheat, consumed widely as a human food is severely affected by biotic stresses. The use of plant beneficial bacteria in the management of biotic stresses is increasing due to its abundance, low inoculant production cost and no environmental risks. This study assessed the impact of bacterial phytopathogen, Xanthomonas sp. on the performance of wheat including phytocompound production and evaluated the biocontrol potential of beneficial rhizobacteria against Xanthomonas induced bacterial leaf streak (BLS) disease. The rhizobacteria, Azotobacter chroococcum Beijerinck, Bacillus megaterium, and Pseudomonas fluorescens produced biocontrol related antimicrobial compounds (ammonia and hydrogen cyanide) and hydrolytic enzymes (cellulase and amylase). In-planta , infected plants had visible BLS symptoms which included yellowing of leaves and necrotic lesions etc. Upon foliar inoculation, Xanthomonas sp. adversely affected growth and significantly reduced dry biomass, plant length, total chlorophyll content and seed yield by 42%, 26%, 59%, and 16%, respectively, over uninfected control. The Xanthomonas infection significantly enhanced the secretion of non-enzymatic and enzymatic phytocompounds, proline, malondialdehyde and reactive oxygen species (ROS) processing enzymes, catalase, superoxide dismutase and glutathione reductase in BLS wheat. Scanning electron microscope (SEM) and confocal laser scanning microscope (CLSM) showed cellular damage in Xanthomonas infected leaf tissues. The bacterial inoculations profoundly enhanced the biological and physiological growth of stressed wheat plants but significantly declined the production of phytocompounds and the activity of the three ROS processing enzymes. These findings demonstrate that microbial antagonists, A. chroococcum , B. megaterium, and P. fluorescens , endowed with potential biocontrol activity provides a promising option for the long-term management of BLS disease, optimize wheat production and fulfil human food demands.