In Vitro and In Planta Antagonistic Effect of Endophytic Bacteria on Blight Causing Xanthomonas axonopodis pv. punicae: A Destructive Pathogen of Pomegranate

Pomegranate bacterial blight caused by Xanthomonas axonopodis pv. punicae ( Xap ) is a highly destructive disease. In the absence of host resistance to the disease, we aimed to evaluate the biocontrol potential of endophytic bacteria against Xap . Thus, in this study, we isolated endophytes from pomegranate plants, identified them on the basis of 16S rDNA sequencing, tested them against Xap , and estimated the endophyte-mediated host defense response. The population of isolated endophytes ranged from 3 × 10 6 to 8 × 10 7 CFU/g tissue. Furthermore, 26 isolates were evaluated for their biocontrol activity against Xap , and all the tested isolates significantly reduced the in vitro growth of Xap (15.65% ± 1.25% to 56.35% ± 2.66%) as compared to control. These isolates could reduce fuscan, an uncharacterized factor of Xap involved in its aggressiveness. Lower blight incidence (11.6%) and severity (6.1%) were recorded in plants sprayed with endophytes 8 days ahead of Xap spray (Set-III) as compared to control plants which were not exposed to endophytes (77.33 and 50%, respectively%) during in vivo evaluation. Moreover, significantly high phenolic and chlorophyll contents were estimated in endophyte-treated plants as compared to control. The promising isolates mostly belonged to the genera Bacillus , Burkholderia , and Lysinibacillus , and they were deposited to the National Agriculturally Important Microbial Culture Collection, India.