Uncovering different physiological mechanisms of peanut drought tolerance under mid-season drought in automated Rain-out Shelters
Type of DegreeMaster's Thesis
Crop Soils and Environmental Sciences
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Peanut is an economic cash crop mainly planted in arid and semi-arid regions where the drought causes around 20% loss of peanut production every year. Research suggested that crops have various physiological mechanisms against drought stress, such as reduction of transpiration while maintaining photosynthesis which leads to water use efficiency (WUE), maintaining water extraction through a deeper and more complex root system, and differences in the partitioning of dry matter to pods. There are few field studies about which physiological characteristics are responsible for peanut drought tolerance in the Southeast United States. To find which physiological characteristics are responsible for mid-season drought tolerance in peanuts, a 2-year experiment testing cultivars known for their drought tolerance and sensitiveness was carried out in rain-out shelters. Plants were grown under irrigated conditions and at the beginning of pod filling (70 DAP), the drought treatment started and lasted until 100 DAP, at which time plants were rewatered until harvest. Photosynthetic rate and specific leaf area were measured 4 times at different development stages in 2019 and measured 7 times in 2020. After harvest, pod yield and HI were collected. 13C and 15N isotope discrimination and N content were measured for pods and shoot biomass. HI, seeds Δ13C, total N in the whole plant, photosynthesis, and stomatal conductance were strong and positively correlated with yield under drought. δ15N was negatively correlated with yield under drought. Different varieties have significant differences in photosynthetic rate, pod yield, and carbon isotope discrimination. Moreover, when photosynthesis and stomatal conductance were measured several times during the drought period these parameters had a stronger correlation with yield than Δ13C. In this research, we found two different mechanisms responsible for drought tolerance. The cultivars PI 502120 and AU-17 showed the highest yield under drought due to higher photosynthesis and stomatal conductance probably due to a higher capacity to extract water, and therefore they were classified as water spenders. On the other hand, two other high yield cultivars, AU 16-28 and Line-8 showed relatively high photosynthesis but low stomatal conductance, which means they might have high water use efficiency under drought and therefore were classified as water savers. In order to improve our understanding of the mechanisms involved in tolerance, a combination of physiological and genomics approaches needs to be applied in future research.