Trends since 1900 in the yield potential of Italian-bred durum wheat cultivars

Changes in yield potential brought about by durum wheat breeding in Italy can be used to define future breeding objectives for durum improvement in Mediterranean environments. The grain yield of 20 durum wheat cultivars, grouped according to their period of release, into 'old' (up to 1950), 'intermediate' (1950-1973) and 'modern' (1974-2000), was compared in an irrigated 2-year field trial, in which two sowing dates and two nitrogen fertilisation rates were imposed. The grain yield of the intermediate cultivars was 39% higher than that of those in the old group, but 18% less than that of the modem material. This increase was associated with earliness, kernel number, harvest index and total nitrogen uptake. Total aboveground biomass and individual kernel weight, on the other hand, were largely unaffected by breeding. Sowing date did not affect the ranking of cultivars, although the more modem cultivars benefited most from the availability of more soil nitrogen. By accessing syriacum germplasm, Italian breeders achieved a substantial improvement in the earliness and productivity of durum wheat well before the introduction of Rht genes. The introduction of dwarfing genes reduced lodging susceptibility, increased harvest index, and marginally delayed flowering time. Modem cultivars also out-performed their predecessors both when sown later and when provided with suboptimal levels of N fertiliser. (C) 2007 Elsevier B.V. All rights reserved.