Effects of temperature and nitrogen nutrition on the grain composition of winter wheat: Effects on gliadin content and composition

The effects of two major ennironmental factors, temperature and nitrogen supply, on grain weight, protein content and especially gliadin content and composition were studied with a new sequential extraction method coupled with RP-HPLC separations. The thermal effects after anthesis were studied at canopy level in climate transparent tunnels in 1993, 1994, 1996 and 1997 under natural light. The nitrogen effects a ere studied in field experiments in 1994, 1995 and 1997. Grain weight, protein content, gliadin content and composition were differently modified by temperature and N supply. The % of proteins and gliadins in the flour increased with the increase of temperature and nitrogen supply, whereas the quantity of proteins or gliadins per grain were affected negatively by the high temperatures and positively by N fertilisation. The proportion of omega-gliadins in total gliadin increased with both factors whereas the alpha- and beta-gliadins increased with the temperature and decreased with the N, and gamma-gliadins decreased with the temperature and increased with the N. These different effects of temperature and nitrogen on the gliadin content in proteins and on the gliadins composition of flour were explained by the total quantity of proteins or gliadins accumulated in the grain. It was concluded that the two approaches at flour and grain level are complementary: the first one was useful to characterise the raw material and the second one to understand and model variations of the grain composition. (C) 2000 Academic Press.