Bioprospecting of endophytic bacteria for enhancing plant growth and its effect on the growth and productivity of betel leaf plants

A total of 27 endophytic bacteria isolated from betel leaves were screened for PGP traits using both qualitative and quantitative methods under invitro conditions. All bacterial isolates demonstrated positive results for IAA production, phosphate solubilization, ammonia production, siderophore production, pectinase, lipase, amylase activity, although they show variable result in hydrogen cyanide (HCN) production. Specifically, the bacteria produced IAA in the range of 1.7 to 224.7 µg/ml, solubilized phosphate between 17.8 and 35.17 µg/ml, produced ammonia in concentrations of 0.14 to 0.51 µmol/ml, and exhibited siderophore production ranging from 38.92% to 71.9%. The bacterial isolates were also tested for their tolerance to different pH levels, salt concentrations and temperature. Four top bacterial isolates were selected based on their superior PGP traits, identified through 16S rRNA gene analysis as Pseudomonas aeruginosa , Bacillus velezensis , Enterobacter cloacae and Serratia marcescens . Among these, Pseudomonas aeruginosa showed the most significant enhancement of all growth parameters in betel plants under greenhouse conditions. This research aims to identify potent strains of endophytic bacteria from Piper betle L. that exhibit a broad range of in vitro plant growth-promoting (PGP) characteristics and to assess their effectiveness in promoting plant growth in vivo through greenhouse experiments.