Assistant Research Scientist University of Georgia
Disclosure: Disclosure information not submitted.
Drought is a major abiotic stress limiting crop productivity worldwide. Frequently coupled with low water availability are high temperatures, with limited evaporative cooling exacerbating the effects of heat. Cultivated sunflower is a deep rooting (drought escape) oil seed crop that is vulnerable to temperature stress during grain filling. To determine the connections between root architecture, canopy temperature, and plant growth and yield we grew plots of 288 genotypes of cultivated sunflower under control (irrigated to replenish transpiration) and drought (10% of control treatment irrigation). At the field site (Imperial Valley area, CA, USA) plants could escape drought by tapping groundwater (~2m deep), but could not escape high temperatures ( >35 °C air temperature). We combined high-effort phenotyping (yield traits, root architecture, δ13C fractionation) with drone and tractor based high-throughput phenotyping (height, NDVI, canopy temperature). Drought modestly reduced seed number and 100 seed weight but oil content was largely unaffected. Interestingly, the effect of drought on canopy temperature was more pronounced and increased over the growing season. With temperatures reaching >40 °C under drought for some genotypes. Canopy temperature was a moderate predictor of yield with higher temperatures leading to lower yields in both conditions. Image based root architecture traits (DIRT pipeline) showed drought leading to a less dense and narrower profile. Greater root area and greater density at lower depth was related to lower canopy temperatures. Genome wide association of these traits to 1.5M SNPs showed multiple independent genomic regions underlying variation in yield, canopy, and root traits with limited overlap between traits. Taken together these results highlight the impact of heat during even a modest drought and the importance of root traits in drought escape. Independent genetic control of these traits shows the potential of mixing and matching traits to further improve drought escape and keeping flower heads cool.