Levan differentially primes barley defence against infections by Fusarium graminearum, Rhizoctonia solani and Pyricularia oryzae

Abstract

The widespread use of pesticides poses significant challenges to the safety of agricultural products and the ecological environment. Levan‐type fructans have the ability to act as an induced resistance stimulus, enhancing plant disease resistance, which aligns with the principles of green development. This study showed that levan polysaccharide, produced by Halomonas smyrnnensis levansucrase, could induce the resistance of barley to Fusarium graminearum much better than inulin‐type fructans or low‐molecular‐weight chitosan oligosaccharide. Three different application methods of levan, namely seed soaking, leaf spraying or their combination, all decreased the necrotic areas caused by F. graminearum and Rhizoctonia solani. When inoculated with F. graminearum, the content of hydrogen peroxide, proline or jasmonic acid and the activities of peroxidase and ascorbate peroxidase in levan‐treated barley were higher than those in the control. In contrast, when inoculated with R. solani, the hydrogen peroxide content and peroxidase activity in levan‐treated leaves showed a faster induction than the control at the early priming and the content of proline and methyl salicylate was higher than that of the control. Thus, levan induces distinct pathways in response to different pathogens.

Exploring Synergistic Effects of Levan and Levan‐MetabolizingBacillaceae in Promoting Growth and Enhancing Immunity of Tomato and Wheat

“…Levan and LOS do not cause immediate defense responses (ROS burst) upon application, preventing temporal growth retardation effects (Janse . Data presented here and elsewhere (Lian et al, 2024) reduced B. cinerea disease symptoms on tomato leaves by 25% when applied to the roots (Cawoy et al, 2014) and by 50% on bean leaves when applied to the leaves (Samares et al, 2021a). Foliage treatment with 12.5 g L À1 COS-OGA, a sugar complex of chitooligosaccharides associated with oligogalacturonides (commercially available as Fytosave), resulted in an average 50% reduction in powdery mildew disease symptoms on tomato leaves, depending on the powdery mildew inoculum present in the greenhouse at the start of the experiment (van Aubel et al, 2016).…”

“…More research is required on a wider array of monocot species to conclude whether monocots may be less receptive to treatments with fructans, fructan-metabolizing bacteria and their combinations. However, it was recently demonstrated that levan from Halomonas smyrnensis could generate biological effects on barley, protecting the plants against several diseases (Lian et al, 2024),…”