Effects of Nitrogen and Sulfur Fertilizers on Gliadin Composition of Several Cultivars of Durum Wheat

Four fertilizer treatments were applied to 10 cultivars of durum wheat (Triticum turgidum var. durum L.) in three seasons of designed field trials. The fertilizer treatments were N0S0 ‐ neither N nor S applied; N1S0 ‐ only N applied; N1S1 ‐ both N and S applied; N0S1 ‐ only S applied. It was found, through densitometric SDS‐PAGE, that the relative proportion of different gliadin components was influenced by the distinct regimes, even though our region in the center of the Argentinean Pampa is not considered to be deficient in soil S‐availability. The effects observed were more marked in one particular season of the three studied, were principally associated with the treatment expected to produce the maximum degree of grain S‐deficiency (N1S0), and were consistent with the hypothesis that the relative content of S‐poor gliadins increases under conditions of S‐deficiency, as has been found in related crops. Multivariate reverse‐phase high‐performance liquid chromatography (RP‐HPLC) analysis of samples from the season most affected generally supported these observations, but refined them in identifying quantitative differences between all four fertilizer treatments for the cultivars studied. These findings imply that differences in industrial quality might also be expected between the fertilizer treatments. RP‐HPLC also identified numerous genetically controlled qualitative differences in the gliadins between the cultivars studied, adding to previous published work on these cultivars based on SDS‐PAGE. These observations confirmed that one particular cultivar of very low gluten strength showed a gliadin profile markedly distinct from the remaining cultivars studied.