High Throughput Phenotypic Evaluation of Drought-Related Traits in Soybean.

The effects of drought on soybean physiology during reproductive development were evaluated in a line-source experiment which was established with genotypes previously characterized as fast or slow wilting. This study 1 (2012, 2013) included three water treatments: well watered (WW), moderate drought (MOD), and rainfed (RF). Five fast and five slow wilting genotypes from a population derived from Benning×PI416937 were evaluated in this study. Carbon isotope discrimination (CID) was determined from leaves sampled at late R5 and from seed at harvest as a surrogate measure for water use efficiency. The results indicated that CID values for soybean leaf and seed decreased with increasing drought stress (i.e., higher water use efficiency). Likewise, slow-wilting genotypes had lower CID values for soybean seed compared to fast-wilting genotypes. For this study, irrigation was applied when the estimated soil-water deficit of WW treatment reached 30 mm. Aerial thermal infrared images were taken with a balloon or kite platform to determine differences in canopy temperature. Results showed that canopy temperature increased with decreased water availability. Additionally, slow wilting genotypes had lower canopy temperatures compared to fast wilting genotypes within each of the water treatments. These results indicate that carbon isotope discrimination measurements of leaf and seed and temperature measurements of canopy hold promise for rapidly characterizing drought-related traits in soybean.