Attempts at Avoiding the Yield Constraints of Bread Wheat ( T. aestivum ) in Mediterranean Environments

In bread wheat, in spite of the upward trend of grain yield, the Italian average production remains far below that of Central or Northern Europe. Recognized constraints are water availability to plants and the increase of air temperature during the grain filling period. To quantify these aspects, three varieties remarkably different in several morphophysiological traits were grown for three years under different water regimes in two locations of North and Central Italy. The grain yield potential of the two locations was similar although if in the Southern location the plants were taller, with a denser canopy and a greater number of smaller seeds. Irrigation after flowering increased yield and yield stability; however, at high air temperatures, dry matter accumulation ceased even though water in the soil was abundantly available. These results suggest the possibility of applying irrigation during grain filling, but a more realistic approach seems to be selection of new varieties characterized by moderate carliness and capacity to sustain kernel growth for a longer period even in the presence of high air temperatures.