We have shown that the YM stage of pollen development
is the weakest link in wheat reproductive development.
Drought stress reduces sink strength in both anthers and
ovaries, but the effect on anther and pollen development
is irreversible. At the meiotic stage, the female gametophyte
appears to be more resilient to drought stress than
anthers. We have identified germplasm that is better able
to maintain grain number and pollen fertility under
drought conditions and we have shown that this germplasm
is characterized by an ability to maintain sink
strength in the reproductive organs. Grain size is affected
by water stress conditions from anthesis onwards and germplasm
that is able to maintain grain number is not better
in maintaining grain size. This suggests that the genetic
control for grain number and size is different. The results
of this paper pave the way for QTL identification and
breeding of wheat varieties with higher resilience for
maintaining grain number during reproductive stage
drought conditions.