Biostimulant potential of agro-industrial side-streams - sustainable sugar beet cultivation and drought tolerance in wheat

The biostimulant potential of three agro-industrial side-streams (hydrolysed wheat gluten (HWG), potato protein (PP/PF) and the chitosan derivative KitoFlokk™ (KF/KF200) and two chitosan types (KA and KB) was compared to that of untreated controls and nutrient solution in trials with three sugar beet genotypes (Volga, Armesa, Mustang) and two spring wheat genotypes (204, 276). In general, 1-2 g/kg HWG or PP/PF applied as a soil mix enhanced sugar beet growth and physiology. Sugar beet also responded positively to increasing concentration (4-6 g per kg or L) of chitosan (KF/KF200, KA and KB), irrespective of application method (soil mix, soil drenching, foliar spray). In addition, bio-pellets containing 15% KB consistently improved growth and physiology of sugar beet. Transcriptome analysis attributed the biostimulant effects of HWG and PP/PF to upregulation of genes associated with metabolic processes (e.g. photosynthesis, protein synthesis and aromatic amino acids) compared with untreated controls. In wheat, bio-priming with 2% or 4% KF200 and foliar application of HWG, PP or 2% KF200 enhanced growth and yield components during early and late drought, with wheat genotype 276 showing better yield performance during drought than genotype 204, when primed/sprayed with biostimulants. Therefore side-streams from wheat and potato starch processing (HWG and PF) and chitosan (KA, KB and KF/KF200) from seafood processing, have biostimulant capacity, triggering metabolic processes that improve growth and bio-macromolecules in sugar beet and drought tolerance in wheat when applied as a soil mix, soil drench, foliar spray or bio-pellet.