EFFECT OF HEAT-SHOCK DURING GRAIN FILLING ON THE GLUTEN PROTEIN-COMPOSITION OF BREAD WHEAT

The present study was conducted to determine the role of the variation of the temperature during grain filling on the protein composition of bread wheat evaluated by SE-HPLC. Four cultivars were grown in four t ypical areas of wheat cultivation in Italy; at each location, four dif ferent temperature profiles were imposed during grain filling by antic ipating or delaying sowing date in the South of Italy (Foggia and Cata nia) or by covering the plots with plastic tunnels in the North (Milan o) and in Central Italy (Viterbo). Results indicated that, independent ly of the genotype, growth environment (location) and different temper ature regimes affect quality characteristics by allowing the synthesis of a different amount of total proteins or providing a different patt ern of protein fraction accumulation. In the latter case, more pronoun ced effects were observed during frequent episodes of daily maximum te mperatures above 35 degrees C, particularly in the plots covered with plastic tunnels during grain filling at Milano and Viterbo. At both lo cations, high temperatures seemed to mainly affect the composition of the polymeric fraction: particularly the formation of larger aggregate s, without influencing their total amount. The relative quantity of in soluble polymeric proteins for heat stressed samples was, in fact, sig nificantly lower than those for samples from the normal (control) and late sowings, whereas this situation was completely reversed when the relative amount of the easily soluble polymeric proteins was considere d. The possible influence of temperature on the mechanism by which int ermolecular disulphide bonds are formed and the effect on composition of polymeric fractions during the deposition of storage proteins are d iscussed. (C) 1996 Academic Press Limited