Nitrogen-sulfur fertilisation effects on gluten composition and industrial quality in Argentinean bread wheat cultivars differing in apparent sulfur recovery

Increasing wheat yield and grain quality is crucial for achieving profitable production systems. Genotype has an important role in determining potential grain end-use quality, because it defines the protein subunits stored in the endosperm. Nitrogen (N) and sulfur (S) availability modulate the expression of the genotype by determining variations in quantitative gluten composition. The aim of this work was to analyse the responses of grain quality to N and S fertilisation and relate them to the relative quantitative composition of different subunits of gliadins and glutenins in 24 Argentinean bread wheat cultivars differing in apparent S recovery (ASR), cycle length and protein pattern. Two field experiments were conducted in the Humid Pampas of Argentina. Gluten composition was analysed by electrophoresis and densitometry, and grain quality by N/S ratio, protein content, sedimentation test, and alveograms. Most genotypes presented high quality potential according to their pattern of high molecular weight glutenin subunits, although they differed in grain quality performance. Under an environment of low soil fertility (i.e. where the soil has a low capacity to supply N and S), N fertilisation reduced the sedimentation test values at low S level (67 vs 54 mm, on average) and increased this parameter at high S level (62 vs 81 mm, on average), with different responses among genotypes. Also, S fertilisation at high N level increased dough strength by 52% for long cycle genotypes and decreased it by 9% for those of short cycle. Genotypes with contrasting ASR, cycle length and protein pattern modified the responses of baking strength to S fertilisation in different ways (positive, neutral or negative), whereas genotype x N interaction modified the responses only in their magnitude. Outstanding genotypes (e.g. Klein Proteo) were identified according to baking quality stability. We conclude that S fertilisation had a notable effect on baking quality, especially in long cycle genotypes and a low soil-fertility environment, correcting S deficiency at high N availability. ASR was not a useful classificatory trait for predicting grain quality. Instead, the study of variants for the protein subunits coded by particular genes (e.g. Glu-A3, Glu-B3, Glu-D1x and Glu-D1y) that partially determine baking quality should be intensified, in order to optimise genetic improvement in wheat.