Characterization of Plant Growth-Promoting Potential of Root Nodule Endophytes from Albizia lebbeck (L.) Benth

Abstract

Albizia lebbeck (L.) Benth. is a leguminous tree with significant potential in agroforestry. Root nodules are known to harbour rhizobia as well as non‑rhizobial endophytes with plant growth‑promoting (PGP) traits. The present study was undertaken to isolate and characterize endophytic bacteria from root nodules of A. lebbeck. A total 48 bacterial isolates were isolated and purified from root nodules of A. lebbeck and were screened qualitatively for four PGP traits; IAA production, ammonia production, phosphate solubilization and chitinase activity. Identification of the effective PGP bacterial strains were done by sequencing of 16S rRNA gene. Results revealed that 52.08% of bacterial isolates exhibited IAA production, 50% of bacterial isolates exhibited ammonia production, while 31.25% isolates showed phosphate solubilization. Chitinase activity was present in only one bacterial isolate (Al-DOB7). Pseudomonas sp. Al-DOB7 were identified as multifunctional PGP bacteria and showed all four PGP activity screened. Three bacterial isolates; Rhizobium sp. Al-Am1, Rhizobium sp Al-Kh2 and Ensifer sp. Al-Rs5 exhibited IAA production, ammonia production and phosphate solubilization. Further quantitative screening and greenhouse validation of these nodule-associated bacteria are essential for their sustainable application in agricultural and agroforestry systems.