Effect of high temperatures during grain filling on the amount of insoluble proteins in durum wheat

The effect of the variation of the temperatures during grain filling on the amount of insoluble proteins was evaluated by reversed-phase high performance liquid chromatography (RP-HPLC) in four durum wheat cultivars grown in four locations. At each location four different temperature profiles were imposed during grain filling by anticipating or delaying sowing date in the South of Italy (Foggia and Catania) or by covering the plots with plastic tunnels in the North (Milan) and Central Italy (Viterbo). The more pronounced effects on the amount of insoluble proteins were observed in presence of frequent episodes of daily maximum temperatures above 35 degree C, like in the plots covered with plastic tunnels during grain filling at Milan and Viterbo. In these cases the quantity of insoluble proteins of heat stressed samples was significantly lower than those of samples from the normal (control) and late sowings. However, the extent of the change in the amount of insoluble proteins related to temperature fluctuations appeared to vary with the genotype involved and with their interaction with growth environment. The weakness of doughs observed in heat shocked plants could be explained by a lower degree of polymerization of glutenin subunits. This also leads to the possible effect of temperature on the mechanism by which intermolecular disulphide bonds are formed during the deposition of storage proteins.