Multifunctional Exopolysaccharides from Pseudomonas aeruginosa PF23 Involved in Plant Growth Stimulation, Biocontrol and Stress Amelioration in Sunflower Under Saline Conditions

Abstract

Isolate PF23 selected from among 110 fluorescent pseudomonads, identified as Pseudomonas aeruginosa, displayed salinity tolerance and exopolysaccharides (EPS) production up to 2,000 mM NaCl concentration. EPS-defective mutant PF23(EPS-) of the isolate showed 86 % reduction in EPS production in comparison with wild strain. Defect in EPS production brought loss in salt tolerance capability. Purified EPS obtained from PF23 displayed multiple roles. At low concentration EPS functioned as biocontrol agent, at high concentration EPS behaved as osmoprotective or stress ameliorating metabolite and when introduced in saline soil, served as a plant growth promotor along with seed biopriming agent. Both in planta and in vivo studies were performed taking sunflower as a test crop and it was observed that PF23 showed plant growth promotion and significant biocontrol potential against dreadful phytopathogen Macrophomina phaseolina (under saline conditions). The mutant PF23(EPS-) was ineffective under saline conditions both in growth enhancement as well as in disease suppression. The study reports a potent strain, Pseudomonas aeruginosa PF23, capable of enhancing production of sunflower crop in semiarid regions and minimizing the incidence of charcoal rot disease in sunflower.

Role of salicylic acid from Pseudomonas aeruginosa PF23EPS+ in growth promotion of sunflower in saline soils infested with phytopathogen Macrophomina phaseolina

“…The positive role of bacterial EPS, as an elicitor, for the induction of systemic resistance against various phytopathogens of different crop species has been reported by Prashar et al (2013), Thenmozhi and Dinakar (2014). EPS production under stress conditions act as a strategy to protect bacterial cells from salinity stress damages (Tewari and Arora 2014a;. Both these metabolites being induced under saline conditions may have some connection in between them at biochemical or molecular level.…”

“…EPS produced by PGP microbes is known to intensify soil aggregation, enhance soil texture, increase water holding capacity of soil, reduce water loss during stress conditions and protect plant from pathogenic invaders (Tewari and Arora 2014a). Roberson and Firestone (1992) also reported that EPS producing strains increase root-associated soil and hydrophilization of soil leads to improved supply of nutrients that is responsible for increasing stem width and plant growth promotion.…”

“…EPS producing strain P. aeruginosa PF23 EPS+ and its mutant PF23 EPS− displaying biocontrol against M. phaseolina were routinely grown on Davis minimal medium (DMM) (g/l) supplemented with trace element solution as described by Tewari and Arora (2014a). Strains were grown at 28 °C and maintained on DMM agar slants at 4 °C.…”

“…Combination of PGPR and microbial product(s) for enhancing plant growth particularly under salinized field conditions infested with phytopathogens is a novel approach (Arora and Mishra 2016). In the present study, saline tolerant, EPS producing fluorescent Pseudomonas PF23 EPS+ and its mutant taken from author's collection (Tewari and Arora 2014a) were monitored for SA production. Authors already have reported the role of EPS produced by PF23 EPS+ in plant growth promotion and biocontrol (Tewari and Arora 2014a).…”

“…In the present study, saline tolerant, EPS producing fluorescent Pseudomonas PF23 EPS+ and its mutant taken from author's collection (Tewari and Arora 2014a) were monitored for SA production. Authors already have reported the role of EPS produced by PF23 EPS+ in plant growth promotion and biocontrol (Tewari and Arora 2014a). However, in the present study it was further noticed that the bacterial strain PF23…”