Final grain weight in wheat as affected by short periods of high temperature during pre- and post-anthesis under field conditions

Individual grain weight is an important source of variation for grain yield in wheat. The aim of this study was to investigate the effect of short per iods of high temperature immediately pre-anthesis, or during post-anthesis, on grain weight under field conditions. Thus, two wheat cultivars of diffe rent grain weight potential were sown on four different sowing dates to pro vide different temperature conditions during the pre- and post-anthesis per iods. In addition, for two sowings, acrylic boxes were installed to increas e spike temperature either immediately before anthesis, or during the linea l phase of the grain-filling period. Final grain weight was significantly a ffected by sowing date, genotype and grain position on the spike. Grain wei ght showed a clear relationship with the average temperature of the grain f illing period, but this relationship was either linear or curvilinear, depe nding on the cultivar. Both high temperature treatments, i.e. at pre- or po st-anthesis, significantly diminished final grain weight, and their effect was similar with the exception of heavier grains, which were unresponsive t o the high temperature treatment at pre- anthesis. Finally, a better unders tanding of final grain weight was reached when temperatures from the pre- a nthesis period were included in the analysis of grain weight response to te mperature.