Journal of Pure and Applied MicrobiologyVol. 9 No. 2

Studies on Factors Affecting Root Colonization of Root and Nodule Endophytic Bacteria from Mungbean Rhizosphere

Navprabhjot Kaur1 and Poonam Sharma2

1Department of Microbiology, 2Department of Plant Breeding and Genetics, Punjab Agricultural University, Ludhiana 141 004, India.

Received on 06 April 2015 and accepted on 19 May 2015

 

ABSTRACT

The present study was designed to study the factors affecting the root colonization by plant growth promoting endophytic bacteria. A total of 17 isolates (8 from root and 9 from nodule) of endophytic bacteria from mungbean rhizosphere were selected on the basis of their multifunctional traits and further studied for root colonization and growth parameters under in-vitro conditions. Highest biofilm formation was calculated at 12 hrs ranged between 0.180 to 0.411 (OD 595nm). Enhancement in autoaggregation was recorded after 24hrs (25.6 to 45.3%). Endophytic reactivity to antibiotics revealed that 58.8% of isolates were resistant to ampicillin (10 ?g disc-1). All the cultures exhibited significant increase in percent seed germination ranged from 80.8% to 90.0% in mungbean variety SML 668 and SML832 (except LREB1) as compared to nonbacterized control. Endophytic bacterization improved total length and fresh weight of seedlings in mungbean. Root endophytic Klebsiella sp. LREK25, nodule endophytic Bacillus sp. LNEB1 and Pseudomonas sp. LNEP16 were found to be most promising PGPR showing highest root colonization and seed vigor index. Phenotypic characteristics and genotypic distinctiveness of isolated strain from other phylogenetic neighbours of Klebsiella, Bacillus and Pseudomonas species, strain LREK25, LNEB1 and LNEP16 have been designated as Klebsiella sp. LREK25 (GenBank accession number KF424316), Bacillus aryabhattai LNEB1 (KF853102) and Pseudomonas aeruginosa LNEP16 (KF853103). These potential endophytes can be considered as highly competent microorganisms for better colonization, competitiveness and establishment in rhizosphere for improving mungbean productivity.

Keywords : Biofilm, Endophytic bacteria, Mungbean, Vigor index.