Biocontrol potentiality and plant growth-promoting traits of endophytic Enterobacter cloacae RO2 isolated from Portulaca oleracea L. against Bipolaris sorokiniana

Abstract

In agricultural applications, plant growth-promoting bacteria (PGPB) have demonstrated their efficacy as both biofertilizers and biocontrol agents against several phytopathogens. This study reports, for the first time, the isolation of an endophytic Enterobacter cloacae from the medical plant Portulaca oleracea L., which produces iturin-like lipopeptides effective against B. Sorokiniana that causes severe diseases that affects several important crops. The present study investigates the ability of E. cloacae as a PGPB and a producer of bioactive metabolites that participate in the biological control of Bipolaris sorokiniana. Twelve endophytic bacterial isolates obtained from P. oleracea, grown in El-Sharkia Governorate, Egypt, were examined for their antagonistic activity against B. sorokiniana through the disk diffusion method. Also, the most active isolates (2, 5, 7 and 8) were investigated using a dual culture technique against B. sorokiniana in vitro, and the percentages of inhibition were 43.48, 40.55, 36.60, and 35.57%, respectively. Therefore, the most active endophytic bacterial isolate (2) was molecularly identified as E. cloacae strain RO2 with accession number PV739238. In vitro assessment of PGP traits of E. cloacae strain RO2 proved that it can produce protease, amylase, cellulase, in addition to nitrogen fixation, siderophore production, phosphate and calcium carbonate solubilization and ammonia production. E. cloacae caused irregular mycelial growth and morphological deformation in B. sorokiniana hypha. HPLC analysis of E. cloacae's lipopeptide extract revealed the occurrence of lipopeptide like Iturin that had inhibitory effects on B. sorokiniana. In addition, the growth-promoting potential of E. cloacae was evaluated on wheat (Triticum aestivum L.) seeds bio-primed with it, and the results showed enhanced shoot height, radicle length, fresh and dry weight of seedling as compared to the control. Consequently, E. cloacae strain could be used as biofertilizers and biocontrol agent in agriculture to reduce the risk of chemical pesticides.