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

The aim of this research is to identify potent strains of endophytic bacteria from Piper betle L. that exhibit a wide range of in vitro plant growth-promoting (PGP) characteristics and to assess their effectiveness in promoting plant growth in vivo through greenhouse experiments. A total of 27 endophytic bacteria isolated from betel leaves were screened for PGP traits using both qualitative and quantitative methods. All bacterial isolates demonstrated positive results for IAA production, phosphate solubilization, ammonia production, siderophore production, pectinase activity, and 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 38.92–71.9%. Four bacterial isolates, selected for their superior PGP traits, were 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.