Bacteria isolated from roots and rhizosphere of Vitis vinifera retard water losses, induce abscisic acid accumulation and synthesis of defense‐related terpenes in in vitro cultured grapevine

Abstract

Eleven bacterial strains were isolated at different soil depths from roots and rhizosphere of grapevines from a commercial vineyard. By 16S rRNA gene sequencing 10 different genera and 8 possible at species level were identified. From them, Bacillus licheniformis Rt4M10 and Pseudomonas fluorescens Rt6M10 were selected according to their characteristics as plant growth promoting rhizobacteria (PGPR). Both produced abscisic acid (ABA), indole-3-acetic acid (IAA) and the gibberellins A1 and A3 in chemically-defined medium. They also colonized roots of in vitro grown Vitis vinifera cv. Malbec plants. As result of bacterization ABA levels in 45 days-old in vitro plants were increased 76-fold by B. licheniformis and 40-fold by P. fluorescens as compared to controls. Both bacteria diminished plant water loss rate in correlation with increments of ABA. Twenty and 30 days post bacterization the plants incremented terpenes. The monoterpenes α-pinene, terpinolene, 4-carene, limonene, eucalyptol and lilac aldehyde A, and the sesquiterpenes α-bergamotene, α-farnesene, nerolidol and farnesol were assessed by gas chromatography-electron impact mass spectrometry analysis. α-Pinene and nerolidol were the most abundant (µg per g of tissue in plants bacterized with P. fluorescens). Only α-pinene, eucalyptol and farnesol were identified at low concentration in non-bacterized plants treated with ABA, while no terpenes were detected in controls. The results obtained along with others from literature suggest that B. licheniformis and P. fluorescens act as stress alleviators by inducing ABA synthesis so diminishing water losses. These bacteria also elicit synthesis of compounds of plant defense via an ABA independent mechanism.

Abscisic Acid as Pathogen Effector and Immune Regulator

“…Plants synthesize their ABA via their plastids (an organelle that does not exist in fungi or animals) as a compound derived from large (40 carbons) carotenoid precursor molecules generated via the plastidial 2- C -methyl-D-erythritol 4-phosphate (MEP) pathway (Schwartz et al, 2003; Finkelstein, 2013). Rhizosphere and endophytic bacteria, such as Achromobacter, Bacillus and Pseudomonas , have all been shown to produce ABA in axenic cultures (Forchetti et al, 2007; Salomon et al, 2014). Also marine Streptomyces isolates have been shown to produce ABA and several other phytohormones without any obvious interaction with plants (Rashad et al, 2015).…”

“…Emerging evidence also indicate that ABA plays an important role in compatible interactions in mutualistic plant-microbe interactions (Stec et al, 2016). For example, ABA is promoting infection and establishment of compatible interactions with arbuscular mycorrhizal fungi (Herrera-Medina et al, 2007; Charpentier et al, 2014; Fracetto et al, 2017) and several kinds of root-associated bacteria produce ABA in the rhizosphere (Salomon et al, 2014). Not only does ABA suppress immune responses, but immune responses are also able to suppress ABA signaling.…”

Endophytic Bacterium Pseudomonas fluorescens RG11 May Transform Tryptophan to Melatonin and Promote Endogenous Melatonin Levels in the Roots of Four Grape Cultivars

“…Numerous plant-associated microbes are beneficial components of plant micro-ecosystems (Chebotar et al, 2015) because they provide protection against phytopathogens (Lindow and Brandl, 2003; Jetiyanon, 2007), enhance mineral nutrient acquisition (Elbeltagy et al, 2001; Johnson, 2008; Richardson et al, 2009), and help plants withstand abiotic stresses (Castiglioni et al, 2008; Zhang et al, 2008; Khan et al, 2015). The most researched role of plant-associated microbes is their potential to regulate plant growth by acting as suppliers of diverse phytohormones, including gibberellins (Bottini et al, 2004; Shahzad et al, 2016), indole acetic acid (Patten and Glick, 1996; Etesami et al, 2014), cytokinins (Ie et al, 2001; Arkhipova et al, 2007), jasmonates and abscisic acid (Forchetti et al, 2007; Belimov et al, 2014; Salomon et al, 2014). …”

Root-associated bacteria promote grapevine growth: from the laboratory to the field

“…These powerful properties have been shown at laboratory scale using in vitro assays (Zamioudis et al 2013;Salomon et al 2014) , soil microcosm tests (Sabir et al 2012;Suarez et al 2015), and field-like conditions (Shishido 1996;Chanway 1997;Aslantas et al 2007;Magnin-Robert et al 2013;Rolli et al 2015). However, the role these symbionts play in field-scale agricultural environments remains poorly understood (Bashan et al 2014 and reference therein; Berger et al 2015;GarciaSeco et al 2015;Garima and Nath 2015).…”