Physiological Characteristics Determining Drought Tolerant in Peanuts.

90% peanuts in Alabama grows under rain-fed conditions, which makes the crops sensitive to drought stress during the pod filling stage. Under these conditions, achievement of high peanut productivity is mainly based on whether or not that cultivar is drought tolerant. Although breeders and farmers have been selecting for drought tolerant peanuts for years, the physiological characteristics responsible of drought tolerance are still unknown. In other crops, some drought tolerant cultivars are able to maintain a higher photosynthetic activity for longer at the expense of higher water use that they obtain thanks to deeper roots. By the contrary, other drought tolerant cultivars shut down the stomata and perform a lower photosynthesis in order to save water. The objective of this experiment was to test which of these two strategies are more prevalent in drought tolerant cultivars developed at Auburn University Breeding Program. With that aim four different peanut cultivars, two selected for being drought tolerant, one selected as drought sensitive, and a commercial check (G06G) were planted at two locations under irrigation and rainfed conditions. After the first flower, 5 sampling times were performed until maturity including physiological measurements such as photosynthesis, LAI, fluorescence, SPAD, and soil moisture. In those same times biomass samples were performed to study the C allocation in the different aboveground organs. Aboveground biomass was separated by different parts and weighted. The results indicated that photosynthesis, LAI and seed biomass was lower in rain-fed conditions, and differences between cultivars were observed.