Manipulation of the post-flowering source/sink ratio differentially affects protein composition and gluten quality in contrasting bread wheat genotypes

Abstract

Studies of the impact of assimilate availability during grain filling on protein composition and gluten quality ofbread wheat are scarce. Therefore, this work aimed to analyze the responses of wet gluten percentage, SDSsedimentation index, and protein composition to changes in the source/sink (S/S) ratio (post-flowering growthper grain) in six Argentinean wheat genotypes contrasting in baking aptitude (three quality groups), as well as toevaluate its interaction with early nitrogen-sulfur fertilization. For two years, rainfed field trials were carried outin the Humid Pampas in Southern South America, applying manipulative S/S treatments (shading, defoliation,thinning, and trimming). Gluten percentage showed a negative linear trend against the increase in S/S ratio withdifferences among genotypes even within the same quality group (slope range: 0.0248 to 0.6566). The associationsbetween the main protein fractions (i.e., GLI/GLU, HMW/LMW) with the S/S ratio were not significant,while the proportions of specific high molecular weight glutenin subunits were relevant, such as Glu-A1x/HMW (slope range: 0.00027 to 0.00147) and Glu-D1y/HMW (0.00029–0.00139). Early nitrogen-sulfurfertilization increased the influence of the S/S ratio on gluten percentage while stabilizing the sedimentationindex. These results apport another approach, based on S/S ratio, to understanding the determination of grainquality under changing contexts.