Isolation and selection of fluorescent pseudomonads based on multiple plant growth promotion traits and siderotyping

Abstract

Fluorescent pseudomonads, acclaimed plant associated bacterial group, are well-known plant growth promoting-biocontrol agents in rhizosphere arena. In this study, 144 fluorescent pseudomonad isolates from rhizosphere soil samples were screened with King's medium B supplemented with 8-hydroxyquinoline (8-HQ) chelator and comprehensively profiled for plant growth promotion viz., production of indole acetic acid (IAA), siderophore, ammonia, hydrogen cyanide, motility, phosphate solubilization, root growth promotion, and biofilm forming ability, along with two known control strains of pseudomonads. Iron and IAA regulated secondary metabolite siderophore production were investigated quantitatively. All isolates were positive for ammonia production and motility; 46% isolates were positive for hydrogen cyanide, 44% shown positivity for phosphate solubilization, and 40% isolates for siderophore production. Siderotyping showed production of hydroxamate type of siderophores which are known to be more efficient biocontrol agents. All isolates stimulated root growth to varying extent and had potentiality to form biofilms, a critical constituent for survival on different environments. Forty-two isolates of pseudomonads showed antagonistic behavior against the deleterious fungal pathogen Fusarium oxysporum (MTCC1755). Based on the above observations and statistical analysis, 11 isolates were shortlisted for further scrutiny. The study of biogeographic correlation and secondary metabolite profiling in association with plant growth promotion focalizes significant assessment on the behavior and antagonistic action, which probably brings out a competent biocontrol agent in a sustainable eco-friendly dimension.

Diversity and Metabolic Potential of the Dominant Culturable N<sub>2</sub>-Fixing and P-Solubilising Bacteria from Tea (<i>Camellia sinensis</i> L.) Rhizosphere

“…A number of bacterial species belonging to genera Bacillus, Pseudomonas, Paenibacillus, Stenotrophomonas, Arthrobacter, Serratia, and Burkholderia were the most common NFB and PSB in the tea rhizosphere. All genera encountered, according to this study, have been already described as PSB and/or BNF bacteria, such as Pseudomonas [4,25,26], Bacillus and Paenibacillus [27,28], Burkholderia [4,24,29], and Arthrobacter [10]). B. pumilus was the most dominant NFB and PSB in the acidic tea rhizosphere, followed by B. subtilis, B. licheniformis, B. laevolacticus, P. fluorescens, P. putida, S. maltophilia and B. megaterium.…”

Modified microplate method for rapid and efficient estimation of siderophore produced by bacteria

“…The present study also proved that fluorescent pseudomonads were the most proficient siderophore producers in comparison with other strains. Many researchers have reported fluorescent pseudomonads to be prolific producers of siderophores (Pandey et al 2005 ; Subramanian and Satyan 2014 ; Pattan et al 2017 ; Kotasthane et al 2017 ). In fact, P. aeruginosa are amongst the most efficient producers of siderophores reported from rhizosphere or other habitats as shown by this work also (de Villegas et al 2002 ; Unni et al 2014 ; Sasirekha and Srividya 2016 ).…”

Promising bacterial genera for agricultural practices: An insight on plant growth-promoting properties and microbial safety aspects

“…has been reported. In addition, HCN (Subramanian and Satyan, 2014) and ammonia production (Rashid et al, 2012;Subramanian and Satyan, 2014) as well as phosphate solubilization (Subramanian and Satyan, 2014) and nitrogen fixation (Pham et al, 2017) by Pseudomonas spp. was described.…”