CONSEQUENCES OF WHEAT BREEDING ON NITROGEN AND PHOSPHORUS YIELD, GRAIN NITROGEN AND PHOSPHORUS CONCENTRATION AND ASSOCIATED TRAITS

Several studies have analysed the effects of wheat breeding on dry matter accumulation and partitioning. but little has been done to understand the effects on nutrient economies. The objective of this study was to identify the changes produced by wheat breeding in the economy of nitrogen and phosphorus under field conditions. Two experiments were carried out with seven genotypes (including a commercial hybrid) representing different eras of plant breeding. Wheat breeding has increased grain nitrogen and phosphorus yield but total absorbed nutrients have not shown any trend during this century. The main attribute closely related to the increase in grain nitrogen and phosphorus yields was their harvest indices. The higher nutrient partitioning in the newer cultivars was associated with lower grain nitrogen and phosphorus concentrations in their grains. Therefore, there was a negative effect of genetic improvement in grain nitrogen and phosphorus concentrations. The main cause for the decreased concentration of these nutrients in the grains of the modern cultivars appeared to be a dilution by an even more increased dry matter partitioning. It is suggested that future breeding should be aimed to select for higher nitrogen uptake as a way to increase the level of this nutrient in grain. (C) 1995 Annals of Botany Company