Polysaccharide Elicitor from the Endophyte Bionectria sp. Fat6 Improves Growth of Tartary Buckwheat under Drought Stress

Drought can limit the growth and reduce the yield of crops, but the safeand effective bio-approach to improve the drought resistance of crops is very little. We conducted an experiment in which we monitored the effects of polysaccharide from the endophyte Bionectria sp. Fat6 on the growth of Tartarybuckwheat (Fagopyrum tataricum (L.) Gaertn) seedlings under control anddrought-stressed conditions by determining gas exchange, photosynthesis parameters, photosynthetic pigment contents, and metabolite accumulation. Resultsindicated that the polysaccharide from endophyte stimulated plant growth andincreased the aboveground biomass, root mass, and root/shoot ratio of Tartarybuckwheat. Application of the polysaccharide to drought-stressed plants resultedin a significant increase in the net photosynthetic rate, stomatal conductance, andtranspiration rate of Tartary buckwheat and decreased the intercellular CO₂ concentration. The contents of chlorophyll a, chlorophyll b, chlorophyll a + b, andcarotenoids in leaves were higher in polysaccharide-treated seedlings than thatin control. Polysaccharide notably increased the soluble protein and proline content and decreased the malondialdehyde content in Tartary buckwheat leaves. Theendophytic polysaccharide may protect Tartary buckwheat against drought byimproving leaf gas exchange and photosynthetic capacity, and altering concentrations of protective metabolites. Together, these changes may compensate for thenegative impacts of drought stress on the growth of Tartary buckwheat. Thus,the polysaccharide from the endophyte Bionectria sp. Fat6 may be an effectivebiotic elicitor and a promising bio-approach to improve Tartary buckwheat production worldwide.