Aim:To investigate the role of the leading saffron endophyte Burkholderia gladioli strain E39CS3 (BG-E39) in the inhibition of corm-rot and induced systemic resistance (ISR) in the host against the saffron specific pathogen, Fusarium oxysporum. Methods and Results: We studied the interaction between BG-E39 and the corm-rot pathogen F. oxysporum in vitro and in vivo. BG-E39 strongly inhibited both the F. oxysporum strains and other saffron-specific and non-specific pathogens used in this study. Confrontation and microscopic analyses revealed that the endophyte possessed fungicidal activity against the pathogens and effectively induced cell death in the mycelia. The endophyte produced chitinases as well as β-1,3-glucanase that may be involved in the pathogen cell wall degradation. BG-E39 did not cause corm-rot in Crocus sativus and the closely related plant, Gladiolus, thus establishing that it is non-pathogenic to these plants. The endophyte reduced corm-rot through antibiosis and enhanced the endogenous jasmonic acid (JA) levels and expression of JA-regulated and other plant defence genes. Conclusions:The bacterial endophyte BG-E39 provides resistance to the host plant against F. oxysporum corm-rot in nature. Significance and Impact of the Study: The current study discovers the role of the saffron endophyte BG-E39 in providing resistance to the host against corm-rot. Therefore, this endophyte is a potential candidate for developing a microbial formulation for the biocontrol of the most common disease of C. sativus.

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