Characterization and management of Pseudomonas syringae pv. syringae, causing basal kernel blight of barley (Hordeum vulgare L.)

Globally, basal kernel blight caused by Pseudomonas syringae pv. syringae (PSS) has been recognized as the most serious diseaseo of barley. Recently, polymerase chain reaction (PCR) based gene sequencing is a more powerful tool to identify bacterial pathogens from seeds as well as other plant materials. The disease can be controlled by chemical treatment in the field which has harmful consequences on the environment and biodiversity. The application of plant extracts for the eco-friendly management of seed-borne pathogens is a popular new biocontrol method. Therefore, this study aimed at isolating and identifying PSS from seeds of barley and assessing the antimicrobial potential of the extracts of some plants viz., Citrus limon, Hibiscus rosa-sinensis, Ricinus communis, Psidium guajava, Murraya koenigii, Withania somnifera, Eucalyptus globulus and Tecomella undulata to promote effective biocontrol strategy. A total of 28 bacterial pathogens were isolated and tested for various biochemical tests. Results of the LOPAT test (+---+) and GATTa test (++--) primarily indicated the presence of PSS. The 16S rRNA gene sequencing was performed on PCR-amplified products with 8F and 1492R primers. The two isolates HV 03 and KASS showed 99.8 and 99.6% homology with strain PSS strain KFB 86 which was isolated from Ficus carica in Serbia. The highest antibacterial activity in vitro was obtained with methanol extract of W. somnifera, P. guajava, E. globulus and M. koenigii. The results specified that the plant extracts which showed promising antibacterial activity may be considered an effective tool for the management of disease caused by PSS in barley.