Abstract
Thirty isolates of fluorescent pseudomonads were obtained from rhizosphere of different crops in Raichur, India. The fluorescent pseudomonad strains were characterized in vitro for biochemical traits, antimicrobial traits, and pyoluteorin antibiotic production. All the isolates that showed fluorescent pigment production under UV light were rod shaped, Gram negative, positive for oxidase, catalase and citrate utilization tests, and negative for indole test. Out of 30 isolates, 07 isolates were positive for HCN production, 15 isolates were positive for H2S production, and all the isolates were positive for siderophore production. Among all the isolates, RFP-22 showed the maximum percent inhibition of mycelium (46.66 %) of Rhizoctonia solani, the pathogen, and the remaining isolates showed the moderate to least inhibition of mycelium growth of R. solani. The 16S rRNA analysis confirmed that the antibiotic positive isolates belonged to genus Pseudomonas. The amplification of 779 bp region in isolates RFP- 4 and RFP-19 corresponded to pyoluteorin antibiotic-coding pltB gene. Further characterization of pyoluteorin antibiotic through TLC and TOF–MS analysis confirmed the presence of pyoluteorin at 274.26 (g/mol) peak and 2.10 min retention time. Biochemical and molecular analyses confirmed the antagonism of Pseudomonas and isolate through pyoluteorin production.
Highlights
Some of the rhizobacteria positively influence on plant growth and health which were referred as Plant Growth Promoting Rhizobacteria (PGPR)
Out of 30 isolates, 07 isolates were positive for hydrogen cyanide (HCN) production, 15 isolates were positive for H2S production, and all the isolates were positive for siderophore production
Further characterization of pyoluteorin antibiotic through thinlayer chromatography (TLC) and Time-of-Flight– Mass spectroscopy (TOF–MS) analysis confirmed the presence of pyoluteorin at 274.26 (g/mol) peak and 2.10 min retention time
Summary
Some of the rhizobacteria positively influence on plant growth and health which were referred as Plant Growth Promoting Rhizobacteria (PGPR). These rhizobacteria are abundant in rhizosheric soil of several crops, and these maintained the ecological balance in niche needed for their survival. These PGPR played a pivotal role in both growth promotion and plant disease control. Biological control of diseases by plant growth promoting rhizobacteria was well-established phenomenon (Shaikh and Sayyed 2015; Shaikh et al 2016). The antibiotics, HCN, H2S, and siderophore have been shown to play a major role in the suppression of several plant pathogens (Handelsman and Stabb 1996; Shaikh et al 2014)
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