Bioprospecting Plant Growth-Promoting Rhizobacteria That Mitigate Drought Stress in Grasses

Abstract

This study reports the application of a novel bioprospecting procedure designed to screen plant growth-promoting rhizobacteria (PGPR) capable of rapidly colonizing the rhizosphere and mitigating drought stress in multiple hosts. Two PGPR strains were isolated by this bioprospecting screening assay and identified as Bacillus sp. (12D6) and Enterobacter sp. (16i). When inoculated into the rhizospheres of wheat (Triticum aestivum) and maize (Zea mays) seedlings, these PGPR resulted in delays in the onset of plant drought symptoms. The plant phenotype responding to drought stress was associated with alterations in root system architecture. In wheat, both PGPR isolates significantly increased root branching, and Bacillus sp. (12D6), in particular, increased root length, when compared to the control. In maize, both PGPR isolates significantly increased root length, root surface area and number of tips when compared to the control. Enterobacter sp. (16i) exhibited greater effects in root length, diameter and branching when compared to Bacillus sp. (12D6) or the control. In vitro phytohormone profiling of PGPR pellets and filtrates using LC/MS demonstrated that both PGPR strains produced and excreted indole-3-acetic acid (IAA) and salicylic acid (SA) when compared to other phytohormones. The positive effects of PGPR inoculation occurred concurrently with the onset of water deficit, demonstrating the potential of the PGPR identified from this bioprospecting pipeline for use in crop production systems under drought stress.

Biofilm Producing Rhizobacteria With Multiple Plant Growth-Promoting Traits Promote Growth of Tomato Under Water-Deficit Stress

“…Among them, 13 strains (61.9%) were identified as Pseudomonas comprising 8 species [P. fluorescens (ESR7 and ESR25), P. azotoformans (ESR4), P. chlororaphis (ESR3 and ESR15), P. poae (ESR6), P. gessardii (ESR9), P. cedrina (ESR12, ESR16, and ESR23), P. veronii (ESR13 and ESR21), and P. parafulva ESB18] and 6 strains (28.6%) were Bacillus with 4 species [B. cereus (ESD3, ESD21, and ESB22), B. horikoshii (ESD16), B. aryabhattai (ESB6), and B. megaterium (ESB9)] ( Table 1). Pseudomonas and Bacillus are well-known plant-growth promoters (Kumar et al, 2012;Backer et al, 2018;Chandra et al, 2018;Naseem et al, 2018;Jochum et al, 2019). Among the identified rhizobacteria, B. cereus (Yan et al, 2017), P. chlororaphis (Selin et al, 2010), and P. fluorescens (Ude et al, 2006) were only reported to form biofilms under laboratory conditions.…”

“…When required, the pots were transferred in the rain shelter. The pot was watered with sterile deionized water to field capacity [when water was leached through bottom holes of the pots, this was considered maximum field capacity (Chandra et al, 2018;Jochum et al, 2019)] every day up to 45 days post planting (DPP). In order to impose water stress, the soil in the root region of each plant was carefully loosened.…”

“…They also induce systemic tolerance by bacterial compounds, expression of antioxidant enzymes, and production of extracellular polymeric substances (EPS) (Timmusk et al, 2014;Naseem et al, 2018;Niu et al, 2018). To date, numerous PGPR (e.g., Azospirillum brasilense, Bacillus cereus, B. subtilis, B. amyloliquefaciens, B. licheniformis, B. thuringiensis, Burkholderia sp., Citrobacter freundii, Paenibacillus polymyxa, Proteus penneri, Pseudomonas fluorescens, P. putida, P. aeruginosa, Ochrobactrum pseudogrignones, and Azotobacter chroococcum) were identified that promote plant growth under water-deficit stress conditions in greenhouse experiments (Wang et al, 2012;Ngumbi and Kloepper, 2016;Vurukonda et al, 2016;Chandra et al, 2018;Martins et al, 2018;Saikia et al, 2018;Van Oosten et al, 2018;Jochum et al, 2019;Meenakshi et al, 2019). However, screening of bacterial strains for PGPR functions in the laboratory/greenhouse not always results in identifying strains that promote plant growth under field conditions.…”

Co-application of bio-fertilizer and salicylic acid improves growth, photosynthetic pigments and stress tolerance in wheat under drought stress

“…It has been known that PGPR belonging to different genera and host plants are capable to alleviate abiotic stresses in plants by augmenting their defense system ( Amna et al, 2020 ; Jochum et al, 2019 ; Yasmin et al, 2017 ). Similarly, the application of SA enhances tolerance to drought stress, thereby not only mitigating the damaging effects of drought stress but also enhancing its tolerance ( Khan et al, 2018 ).…”

Diversidade, mecanismos de atuação e potencial agrícola de bactérias promotoras de crescimento de plantas, usando milho como cultura exemplo

“…agropec. pernamb., Recife,25(2), e2282252020, 2020 fixação de nitrogênio atmosférico CEREZINI;IKEDA et al, 2020;MAHMUD et al, 2020;MORETTI et al, 2020); atua na produção de sideróforos (ZAREI et al, 2019;KOUR et al, 2020;PURI;PADDA;CHANWAY, 2020;TORRES et al, 2020); redução do efeito de estresse oxidativo (FUKAMI et al, 2018;SARKAR et al, 2018;HARMAN;UPHOFF, 2019;JOCHUM et al, 2019;YOOLONG et al, 2019); e como controle biológico e redutor do efeito de fitopatógenos (STURZ;NOWAK, 2000;TIAN;YANG;ZHANG, 2007;VERMA;WHITE, 2018).…”