Abstract
Symbiotic associations with microbes can contribute to mitigating abiotic environmental stress in plants. In this study, we investigated individual and interactive effects of two root endophytic fungal species on physiological and biochemical mechanisms of the crop Chenopodium quinoa in response to salinity. Fungal endophytes (FE) Talaromyces minioluteus and Penicillium murcianum, isolated from quinoa plants that occur naturally in the Atacama Desert, were used for endophyte inoculation. A greenhouse experiment was developed using four plant groups: (1) plants inoculated with T. minioluteus (E1+), (2) plants inoculated with P. murcianum (E2+), (3) plants inoculated with both fungal species (E1E2+), and (4) non-inoculated plants (E-). Plants from each group were then assigned to either salt (300 mM) or control (no salt) treatments. Differences in morphological traits, photosynthesis, stomatal conductance, transpiration, superoxide dismutase (SOD), ascorbate peroxidase (APX), peroxidase, (POD), phenylalanine ammonia-lyase (PAL), phenolic content, and lipid peroxidation between plant groups under each treatment were examined. We found that both endophyte species significantly improved morphological and physiological traits, including plant height, number of shoots, photosynthesis, stomatal conductance, and transpiration, in C. quinoa in response to salt, but optimal physiological responses were observed in E1E2+ plants. Under saline conditions, endophyte inoculation improved SOD, APX, and POD activity by over 50%, and phenolic content by approximately 30%, with optimal enzymatic responses again observed in E1E2+ plants. Lipid peroxidation was significantly lower in inoculated plants than in non-inoculated plants. Results demonstrate that both endophyte species enhanced the ability of C. quinoa to cope with salt stress by improving antioxidative enzyme and non-enzyme systems. In general, both FE species interacting in tandem yielded better morphological, physiological, and biochemical responses to salinity in quinoa than inoculation by a single species in isolation. Our study highlights the importance of stress-adapted FE as a biological agent for mitigating abiotic stress in crop plants.
Highlights
Abiotic stresses linked to climate change are a major factor restricting plant growth and distribution (Bartels and Sunkar, 2005)
Stress tolerance conferred by some fungal endophytes (FE) taxa seems to involve habitat-specific fungal adaptations, i.e., fungal species isolated from plants occurring in areas characterized by high levels of environmental stress are effective at enhancing host stress tolerance (Rodriguez et al, 2008; Giauque et al, 2018)
In a recent study (González-Teuber et al, 2017) characterizing the fungal endophyte community associated with roots of healthy quinoa plants growing in the Atacama Desert (Supplementary Figure 1), Talaromyces and Penicillium were identified as the dominant genera, with T. minioluteus and P. murcianum constituting the two most abundant FE (González-Teuber et al, 2017)
Summary
Abiotic stresses linked to climate change are a major factor restricting plant growth and distribution (Bartels and Sunkar, 2005). Several studies have reported that stress-adapted FE are able to mitigate negative effects of salinity by improving a range of physiological and biochemical plant responses, including photosynthesis, transpiration rate, antioxidant enzyme activity, and concentrations of osmoprotectant molecules, such as proline and soluble sugars (Rodriguez et al, 2008; Zarea et al, 2012; Azad and Kaminskyj, 2016; Li et al, 2017; Molina-Montenegro et al, 2020; Moghaddam et al, 2021) In this sense, stress-adapted FE may potentially be used as biological agents to assist in mitigating abiotic stress in plants
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