Environmental effects on the quality of two wheat genotypes: 1. quantitative and qualitative variation of storage proteins

A new method of sequential extraction of proteins followed by quantitative and qualitative determination by reverse-phased high-performance liquid chr omatography (RP-HPLC) was used to analyse the effect of environmental condi tions (3N fertilisation rates, two varieties, two sites and two growing sea sons) on quantitative and qualitative variation of wheat storage proteins. The results showed that N supply (fertilisation and site) was the most impo rtant environmental factor affecting protein content and composition. The m ost important effect was quantitative: the total protein, protein unit and subunit contents increased with the supply of nitrogen to the grain. As gra in protein increased, the gliadin and glutenin contents and the gliadin to glutenin ratio increased. Gliadin showed a higher correlation with total pr otein content than glutenin. In the variety Rinconada, glutenin content was higher than that in Bancal. As total glutenin increased, both high and low -molecular weight (HMW and LMW) fractions increased and their ratio (HMW/LM W) did not change significantly, despite a slope of LMW subunits two times greater (0.69) than that of HMW fractions (0.31). The quantity of each HMW subunit (RP-HPLC peak) increased with total HMW-glutenin, but their relativ e percentage increased for some peaks and decreased for others. The composi tion of the HMW subunit was more stable in Bancal than in Rinconada. This g eneral pattern of variation was also characteristic of the LMW subunit. Con cerning gliadin composition we noted that the content of different gliadin monomers (RP-HPLC peaks) or pools of monomers (alpha-, beta-, gamma-, omega -gliadin) increased with total gliadin content. The proportion of certain p eaks was stable whereas the contribution of other peaks was related to the variation in gliadin content and depended on the variety. (C) 2000 Elsevier Science B.V. All rights reserved.