The present investigation deals with the phenotypic, biochemical and plant growth promoting activities of root nodule bacteria of Melilotus indicus. A total of 51 isolates were isolated from different sites in the Central Aravalli region. In this study, we found that bacterial colonies showed variation in their colonial characteristics, but most of the colonies were white, opaque, mucilaginous and raised. In salinity tolerance, most of the isolates showed high tolerance and grew up to 4-5% salt concentration, but growth was reduced. In the pH tolerance test, all isolates showed growth from pH 5 to 10. In our investigation, we found that root nodule bacterial strains of Melilotus indicus plants have diverse biochemical and plant growth promoting activities. Sugar utilization and antibiotic resistance varied among isolates; fructose was the most utilized sugar, while adonitol was the least. Most isolates were resistant to nitrofurantoin and carbenicillin. Catalase and oxidase activities were present in most isolates. Many isolates produced IAA (42), ammonia (43), and solubilized phosphate (14). Pectinase, cellulase and amylase activity were also noted in a few isolates. The findings highlight the functional diversity of Melilotus indicus root nodule bacteria and their potential applications in sustainable agriculture. Overall results indicated that Melilotus indicus is associated with a wide range of rhizobia. Such type of root nodule bacterial strains can be utilized as a part of biofertilizers to enhance legume crop productivity, sustainable agriculture and reduce the use of chemical fertilizers.

Keywords:Aravalli; Root Nodule Bacteria; Plant Growth Promoting Activity; Melilotus Indicus