Sweetpotato Cultivar Responses to Interactive Effects of Temperature, Drought, and Carbon Dioxide.

Projected changes in climate warrants developing climate-ready agronomic crops. Among the abiotic stress factors, temperature and drought either alone or in combination impact crop growth yield. The objective of this study were to test the hypothesis that sweetpotato cultivars (Beauregard, Hatteras, and Louisiana 1188) differ in their response to carbon dioxide concentrations (410 and 760 µmol mol^-1), temperature (30/22 and 38/30^oC), and drought stress (well-watered, 100% evapotranspiration, ET and 50% ET) and their interactions. A control treatment consisted of 30/22^oC, 400 µmol mol^-1 (CO₂), and well-watered plants. All treatments were imposed at planting with the exception of irrigation treatments, which were imposed at 36 days after transplanting (DAP) and continued to 83 DAP. Plant growth and developmental parameters and plant-component dry weights were measured at the end of the experiment. Gas exchange, pigments and cell membrane stabilities were measured several times during the experiment. Treatment variables significantly affected all the measured parameters in all cultivars. Cultivars differed significantly for many of the measured parameters. Well-watered conditions favored stem and leaf growth more than storage root growth. Elevated carbon dioxide ameliorated some of the damaging effects of drought and high temperature in all the cultivars. Elevated temperature either alone or in combination depressed storage root yield in all cultivars. Cultivars were classified based on total stress response index, developed from the cumulative sum of response indices of vegetative, physiological, and parameters, varied among the three cultivars. Among the three cultivars tested, Hatteras (+23.92) was classified as drought and temperature tolerant and Beauregard (-12.61) and Louisiana 1188 (-12.67) were identified as drought and high temperature sensitive. This suggests that large scale screening of sweetpotato germplasm for abiotic stresses are needed to develop climate-ready germplasm.