Plant Probiotic Endophytic Pseudomonas flavescens D5 Strain for Protection of Barley Plants from Salt Stress

Abstract

Soil salinity has become a global issue that is directly related to land degradation and results in many changes in climate, ecosystem services, and biodiversity. The present study focuses on the investigation of beneficial properties of a plant probiotic bacterial strain as an eco-friendly and sustainable approach to promote crop growth in saline soil. The endophytic halotolerant strain Pseudomonas flavescens D5 isolated from common chicory (Cichorium intybus L.) was able to grow on a medium containing 15% NaCl; produced indole-3-acetic acid (45.2 μg mL−1) and polyhydroxyalkanoate (1.72 g L−1); and had amylolytic, cellulolytic, and proteolytic activities. Polyhydroxyalkanoate had a pronounced antifungal activity against Fusarium graminearum, F. solani, F. oxysporum, and Alternaria alternata. Under salt stress conditions, inoculation with Ps. flavescens D5 increased the shoot biomass of barley plants by 8–30%, root biomass by 7–20%, chlorophyll a by 18–52%, and chlorophyll b by 7–15%. The content of proline decreased by 1.5–1.8 times. An increase in the activity of antioxidant enzymes (catalase, guaiacol peroxidase, and ascorbate peroxidase) was determined. In inoculated plants growing in saline soil, the content of Na+ ions was lower by up to 54.8% compared to control. This strain is promising for stimulating plant growth and protecting them from diseases and other adverse environmental factors, including salt stress.

Endophytic Fungi from Salt Adapted Plants Confer Salt Tolerance in Barley

“…Furthermore, Ignatova et al (2022) found that the endophytic halotolerant strain Pseudomonas flavescens D5 isolated from chicory had a complex of beneficial effects on plants under abiotic stress including IAA synthesis and enzymatic activity (amylolytic, cellulolytic, and proteolytic).…”

Improving crop salt tolerance through soil legacy effects

“…Moreover, beneficial rhizosphere microorganisms in plants can not only enhance salttolerant properties but also synergistically improve plant responses to salt stress by altering physiological growth processes, including seed germination, morphological structure, and biomass accumulation and partitioning (Pan et al, 2020). Regarding the inoculation of beneficial microbial strains to help crops tolerant salinity, studies have demonstrated that inoculation with Pseudomonas flavescens D5 strain effectively increased the biomass and antioxidant enzyme activities of barley, while reducing the adverse effects of salt stress on barley (Ignatova et al, 2022). Inoculation of candidate strains of Azotobacter has also been found to increase the potassium-sodium ratio, polyphenol and chlorophyll content, and decrease proline concentration in maize, thereby alleviating salt stress in maize by integrating multiple mechanisms (Rojas-Tapias et al, 2012).…”

Biopolymers as Seed-Coating Agent to Enhance Microbially Induced Tolerance of Barley to Phytopathogens

“…flavescens D5, and pullulan, produced by the yeast strain A. pullulans C7, were used. PHA was included in the mixture due to its antifungal properties, as previously identified in earlier studies [15,16].…”

“…Furthermore, some PHAs exhibit antagonistic activity against bacteria [13,14]. In our previous studies, we demonstrated that PHA produced by the strain Pseudomonas fluorescens D5 has pronounced antifungal activity against Fusarium graminearum, Fusarium solani, Fusarium oxysporum [15], and Penicillium expansum [16].…”