Pseudomonas fluorescens Rt6M10 ameliorates the response of Arabidopsis thaliana to salt stress

COHEN A C; AGÜERO F; GONZÁLEZ, C; BOTTINI R; PICCOLI P N

La Falda

Workshop; II Latin american PGPR worshop; 2014

II PGPR Latinoamérica

Introduction Rhizobacterial species that stimulate plant biomass production and increase crop performance are defined as plant growth promoting rhizobacteria (PGPR). Pseudomonas sp. are a well-studied group of bacteria that promote plant growth because of their competitive ability to survive and to respond rapidly to environmental modifications. Furthermore, this group of bacteria has been studied as biocontrol agents against plant diseases. In a previous work, our group isolated Pseudomonas fluorescens Rt6M10 from roots and rhizosphere of grapevines from a commercial vineyard. P. fluorescens Rt6M10 was able to produce abscisic acid (ABA), indole-3-acetic acid (IAA) and the gibberellins A1 and A3 in chemically-defined medium. Also, the strain colonizes roots of in vitro grown Vitis vinifera cv. Malbec plants and reduces plants water loss rate in correlation with increments of ABA (Salomon et al. 2013). The aim of this study was to evaluate the effect of P. fluorescens Rt6M10 in plants of A. thaliana Col-0 subjected or not to salt stress conditions Materials and methods Seeds of Col-0 were surface disinfected and placed in plastic pots containing peat moss and perlite. Then, pots were put into each tray and located in a growth chamber with a 12/12 h photoperiod (100 μmolm?2 s?1), 22 ±2º C. The plants were watered to keep soil water status close to field capacity. Plants with two fully expanded leaves were inoculated in the root with 10 μL of PBS containing 106 CFU mL?1 of P. fluorescens Rt6M10 in PBS (I) or with 10 μL of with PBS. After that, some 30-day-old plants were subjected to well-watered (W) or salt stress (S, 100 mM NaCl) conditions, resulting in the following treatments: (1) W, (2) W+I, (3) S and (4) S+I. The treatments were arranged in a completely randomized design. After 60 days, stomata and total number of leaf epidermal cells, leaf area (LA), photosynthetic and photoprotective pigments, relative leaf water content (RLWC) and the dry weight (DW) of rosettes were measured. Also, the percentage of plant survival and the total seeds production per plant (yield) were evaluated Results P. fluorescens Rt6M10 increased LA and the stomatal index, augmented photosynthetic and photoprotective pigments levels, RLWC and DW and retarded water losses. Also inoculation increased growth, dry weight, seed yield, photosynthetic and photoprotective pigments so improving survival in plants submitted to salt stress. The S+I plants reached the wilting point later than S plants, indicating that inoculation alleviated the saline stress. This is the first study showing physiological mechanisms by which P. fluorescens Rt6M10 is able to counteract salt effects in Arabidopsis plants helping the plant tissues to tolerate conditions of salt stress. Conclusion Inoculation of Arabidopsis with P. fluorescens Rt6M10 improved the vegetative and reproductive success of the plant´s performance, especially under salt stress. This opens new alternatives for a strategy against salt stress. Areas temáticas propuestas: Taxones PGPR [Bacillales, Azospirillum, Pseudomonas, actinomycetes, y otros] [1] e Interacciones bióticas y abióticas [7]