Drought is one of the major constraints limiting crop production globally. Commonly
drought can be prevented by irrigation. However as modern agriculture utilises more
than three quarters of the available freshwater, increasing irrigation might not be a
viable solution due to increased concerns on environmental sustainability. Future
growth in the global population predicts that the agricultural output will have to
increase considerably if malnutrition and famine are to be prevented. On this basis,
the development of crops capable of producing higher yields under water scarce
situations is being developed. The fourth most commonly grown crop, potato
(Solanum tuberosum L.) has the potential of providing nourishment for a larger part
of the increasing population. However potato is known to be drought sensitive, which
renders it unsuitable for future climate scenarios. If potato is to be a part of the
solution the crop has to be able to tolerate drought. In this study, a dihaploid potato
mapping population has been used to investigate clonal performance in intrinsic
water use efficiency (WUEi) under progressive drought achieved in greenhouse and
under field conditions. The mapping population revealed relative large differences in
WUEi and parameters influencing WUEi. It was found that three clones had an
increased WUEi. In the greenhouse, net photosynthetic rate (An) was found to
attribute to the variation in WUEi. Also An was shown to be affected by the plant
nitrogen metabolism. However, under field conditions, stomatal conductance (gs)
seemed to be the primary factor influencing WUEi. Modelling on gs revealed the
simplistic Ball-Woodrow-Berry model to perform better than other tested models.
Model accuracy was however not different and all models predicted gs reasonably
well. In addition, to achieve progression in the development of drought tolerant crop
cultivars, faster screening methods have to be developed. Here, it was found that the
chlorophyll content index could be a useful screening method for higher WUEi under
greenhouse conditions. However, such methods must rely on physiological trait
evaluation in conjunction with agronomical trait evaluation.