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

Abstract

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 × 106 to 8 × 107 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.

Antibacterial Activity and Phytochemical Screening of Tagetus erecta L. and Pelargonium Graveolens Against Xanthomonas Axonopodis Pv. Punicae

“…It is considered as the "Fruit of Paradise" because it is most economically benificial and it shows various medicinal properties. 1 Maharashtra, Karnataka, Andhra Pradesh, Rajasthan, Gujarat, and Tamil Nadu are among the Indian states where it is cultivated. 2 In field this plant is susceptible to various diseases namely Anthracnose caused by Colletotrichum sp., Fruit blight caused by Alternaria sp., Leaf spot and fruit spot caused by Cercospora sp., Scab caused by Sphaceloma sp., wilt caused by Ceratocystis fimbriata and Fusarium oxysporum and bacterial blight caused by Xanthomonas axonopodis pv.…”

“…In India it is resulting in severe production losses of about 60-80% depending on disease severalty. 1 In the year 2000, about 90% of Karnataka's pomegranate cultivated land was damaged in the districts of Bagalkot, Belgaum, Bellary, Bijapur, Chitradurga, Gulburga, Koppal, Raichur, and Tumkur. 4 Xanthomonas axonopodis pv.…”