Water-saving potatoes: exploring and characterizing drought tolerance mechanisms

The world’s third most important food crop, potato, suffers yield reductions during drought stress. Drought scenarios are predicted to become more frequent and severe due to climate change. Therefore, we investigated the feasibility of improving drought tolerance in potato using a set of 103 European potato cultivars. We employed a multidisciplinary approach in our study including the phenotyping of multi-location and multi-year field trials, modelling of potato canopy growth and tuber size distribution, association mapping of tuber size distribution parameters with a 14K SNP array, magnetic resonance imaging of xylem and phloem conduits, microscopic study of stem cross-sections and transcriptomic analyses. We observed that late foliage maturity and a delayed attainment of maximum canopy cover favoured tuber yield during drought conditions. We found a marker-trait association of a region on chromosome three with marketable tuber size and spread of tuber size distribution under drought. Our findings indicate that water and assimilate transport are critical for carbon partitioning to tubers during drought. We observed that increased xylem density per unit stem area and reduction of xylem vessel diameter under drought contributed to tolerance. An integration of these findings in potato breeding programs will facilitate the improvement of drought tolerance in potato.