Plant growth promoting potential of rhizobacteria from Ulmus wallichiana: An endangered plant of Western Himalayas

This paper presents a pioneer study on the evaluation of plant growth promoting potential of bacteria associated with rhizosphere of Ulmus wallichiana, considering the endangered status of this taxon. Ulmus wallichiana (family: Ulmaceae) is a rare and endemic mountain tree of western Himalayas and is one of the richest emporiums for medical taxa. Three sites viz., Chansari, Jari and Naggar were selected for the collection of rhizospheric soil samples of Ulmus wallichiana in Kullu district of Himachal Pradesh, India. Collected samples were processed for the enumeration of rhizobacteria using Standard Plate Count Technique. In total, 21 different bacterial morphotypes were obtained from all the samples. All the isolates were screened for their multifarious plant growth promoting attributes viz., phosphate solubilisation, nitrogen fixation, siderophore, HCN, ammonia production and lytic enzymes production etc. Out of total 21 isolates, 9 were found to be P-solubilizers while 7 were siderophore producers. All the isolates were found to be positive for nitrogen fixing ability as well as ammonia production. Similarly, all isolates showed the production of IAA-like auxins ranging from 2.2-187.8 μg mL-1. These rhizobacteria were also screened for their lytic enzymes production. Of these, only 6, 2, 3 and 1 isolates displayed considerable protease, pectinase, lipase and cellulase activities, respectively. Evaluation of their in-vitro PGP potential suggests their substantial role as growth promoters and biocontrol agents.