Promoting the growth of Sulla flexuosa L. by endophytic root nodule bacteria authors and affiliations.

Legume plants rely upon multipartite interactions between rhizobia and bacterial endophytes within root nodules to facilitate plant growth. This study aimed to isolate and identify indigenous endophytic bacteria from root nodules of Sulla aculeolata L. in Northeast Morocco. Based on their tri-calcium phosphate (TCP) solubilization capacity, five endophytes were chosen for further evaluation of their plant growth traits. All isolates were hydrogen cyanide (HCN) and siderophore producers, while only BCH24 tested positive for ACC deaminase activity. Indole-3-acetic acid (IAA) synthesis ranged from 1.27 mgL to 2.89 mgL, while soluble phosphate concentrations was between 7.99 mg L and 110.58 mg L. Additionally, all the endophytes were able to produce more than two lytic enzymes. Based on the analysis of 16 S rRNA gene sequences five isolates were identified as Enterobacter sp (BCH13, BCH2), Pseudomonas sp (BCH16, BCH24), and Serratia sp (BCH10). The strains inhibited the growth of three phytopathogenic fungi, with BCH13 exhibiting the highest rate against Aspergillus ochraceus (45%), followed by BCH24 against Fusarium oxysporum (40%) and Botrytis cinerea (35%), respectively. In vivo inoculation of halotolerant strains Enterobacter hormaechei (BCH13) and Pseudomonas moraviensis (BCH16) under gnotobiotic conditions revealed that co-inoculation with Rhizobium sullae KS6 improved plant development compared to single inoculation, making it a promising eco-friendly bio-inoculant for legume Sulla flexuosa L. production.