Grain weight is a trait which has hardly been
exploited for raising genetic yield potential of wheat. A clearer
understanding of physiological determinants of grain weight potential would be
useful in establishing the potential value of this trait in future breeding
programs. The objective of this study was to improve understanding of how
intra-spikelet competition for assimilates pre- and post-anthesis affect grain
weight potential, and to evaluate possible mechanisms determining final grain
weight in wheat. Two experiments were carried out under field con-ditions.
Proximal or distal grains from the two central spikelets of spikes of three
synthetic hexaploid lines were detached at heading or 7 d after anthesis.
Synthetic wheats were used since they represent a potential source of genetic
variability for grain weight potential. Carpel size at anthesis and grain
weight during the grain filling period were measured. The de-graining
treatment at heading significantly increased grain weight, especially in
distal posi-tions. On the contrary, the de-graining treatment carried out
after anthesis caused no increase in final grain weight. The largest response
to pre-anthesis de-graining occurred in grain positions with the lowest grain
mass. In addition, the effect of de-graining prior to anthesis was associated
hyperbolically with weight of carpels at anthesis within each grain position.
Therefore, carpel weight at anthesis could be partially associated with the
regulation of grain weight potential.