Inoculation of Brevibacterium linens RS16 in Oryza sativa genotypes enhanced salinity resistance: Impacts on photosynthetic traits and foliar volatile emissions

Abstract

The emission of volatiles in response to salt stress in rice cultivars has not been studied much to date. Studies addressing the regulation of stress induced volatile emission by halotolerant plant growth promoting bacteria containing ACC (1-aminocyclopropane-1-carboxylate) deaminase are also limited. The objective of the present study was to investigate the salt alleviation potential of bacteria by regulating photosynthetic characteristics and volatile emissions in rice cultivars, and to compare the effects of the bacteria inoculation and salt responses between two rice genotypes. The interactive effects of soil salinity (0, 50, and 100 mM NaCl) and inoculation with Brevibacterium linens RS16 on ACC accumulation, ACC oxidase activity, carbon assimilation and stress volatile emissions after stress application were studied in the moderately salt resistant (FL478) and the salt-sensitive (IR29) rice (Oryza sativa L.) cultivars. It was observed that salt stress reduced foliage photosynthetic rate, but induced foliage ACC accumulation, foliage ACC oxidase activity, and the emissions of all the major classes of volatile organic compounds (VOCs) including the lipoxygenase pathway volatiles, light-weight oxygenated volatiles, long-chained saturated aldehydes, benzenoids, geranylgeranyl diphosphate pathway products, and mono- and sesquiterpenes. All these characteristics scaled up quantitatively with increasing salt stress. The effects of salt stress were more pronounced in the salt-sensitive genotype IR29 compared to the moderately salt resistant FL478 genotype. However, the bacterial inoculation significantly enhanced photosynthesis, and decreased ACC accumulation and the ACC oxidase activity, and VOC emissions both in control and salt-treated plants. Taken together, these results suggested that the ACC deaminase-containing Brevibacterium linens RS16 reduces the temporal regulation of VOC emissions and increases the plant physiological activity by reducing the availability of ethylene precursor ACC and the ACC oxidase activity under salt stress.

Inoculation of ACC Deaminase-Producing Brevibacterium linens RS16 Enhances Tolerance against Combined UV-B Radiation and Heat Stresses in Rice (Oryza sativa L.)

“…In addition, the inoculated plants resulted in a 8.2%, 9.4%, and 7% increase in the plant dry weight compared to the non-inoculated plants under combined stress conditions at 3, 4, and 5 days after the stress imposition, respectively. Such an increase in the plant dry weight can be corroborated with previous studies in which the inoculation of B. linens RS16 was able to enhance the dry weight of rice [21] and canola [23] under salt stress conditions. In addition, B. linens RS16 has the ability to secrete hormones such as indole-acetic acid and cytokinins that are important for enhancing plant growth and for the ability to decrease stress ethylene levels through its ACC deaminase activity [23].…”

“…The use of ACC deaminase-producing, plant growth-promoting bacteria (PGPB) has shown promising results in the enhancement of plant growth and stress alleviation under various environmental conditions [20][21][22]. However, there have been a lack of studies that explore the effectiveness of bacterial inoculation in enhancing stress tolerance under combined UV-B radiation and heat stresses.…”

“…Such studies will address the potential strategy to enhance plant growth and productivity in the recent climate change scenario. Brevibacterium linens RS16 is a characteristic ACC deaminase-producing bacteria that has the ability to alleviate a varied range of stresses [21][22][23] and recently we reported its ability to enhance tolerance against UV-B radiation in rice by regulating ethylene emission levels [7]. Hence, this study was conducted to evaluate the ability of B. linens RS16 in enhancing the stress tolerance of rice against combined UV-B radiation and heat stresses by monitoring ethylene emission, photosynthetic traits, plant biomass, and DNA damage.…”

Insights Into Microbially Induced Salt Tolerance and Endurance Mechanisms (STEM) in Plants

“…Increased photosynthetic rates and decreased stomatal resistance enhanced the plant biomass of PGPR-inoculated pea plants ( Wang et al, 2016 ). An interesting study by Chatterjee et al (2018) found that treatment of rice plants with ACC deaminase-containing Brevibacterium linens RS16B decreased volatile organic compound (VOC) emissions and enhanced photosynthesis by reducing the availability of ACC and ACC oxidase activity, suggesting that research on volatile emissions during salt stress can reveal new insights related to stress severity and the initiation of secondary metabolism with stress progression. Ansari et al (2019) demonstrated that PGPR inoculation increased root length, chlorophyll pigments, leaf number, relative water content (RWC), stomatal conductance (gs), and photosynthesis rate (Pn) in alfalfa plants under salt stress.…”

Paraburkholderia sp. GD17 improves rice seedling tolerance to salinity

“…In agricultural production, besides genetic breeding of salt-tolerant varieties, improvement of cultivation conditions is an important strategy. For example, optimizing rhizosphere bacterial community has been demonstrated to efficiently enhance plant tolerance to salt stress (Chatterjee et al 2018a(Chatterjee et al , 2018b. Plant growth-promoting rhizobacteria (PGPR) are a group of soil microorganisms, either rhizospheric (free-living) and/or endophytic (in symbiotic association with plant root interior).…”