Genetic Architecture of Phenomic-Enabled Canopy Coverage in Glycine max.

Digital imagery can help to quantify seasonal changes in desirable crop phenotypes that can be treated as quantitative traits. Because limitations in precise and functional phenotyping restrain genetic improvement in the postgenomic era, imagery-based phenomics could become the next breakthrough to accelerate genetic gains in field crops. Whereas many phenomic studies focus on exploratory analysis of spectral data without obvious interpretative value, we used field images to directly measure soybean canopy development from phenological stage V2 to R5. Over 3 years, we collected imagery using ground and aerial platforms of a large and diverse nested association panel comprising 5555 lines. Genome-wide association analysis of canopy coverage across sampling dates detected a large quantitative trait locus (QTL) on soybean (Glycine max, L. Merr.) chromosome 19. This QTL provided an increase in yield of 47.3 kg ha-1 Variance component analysis indicated that a parameter, described as average canopy coverage, is a highly heritable trait (h2 = 0.77) with a promising genetic correlation with grain yield (0.87), enabling indirect selection of yield via canopy development parameters. Our findings indicate that fast canopy coverage is an early season trait that is inexpensive to measure and has great potential for application in breeding programs focused on yield improvement. We recommend using the average canopy coverage in multiple trait schemes, especially for the early stages of the breeding pipeline (including progeny rows and preliminary yield trials), in which the large number of field plots makes collection of grain yield data challenging.

Assessing stream temperature variation in the Pacific Northwest using airborne thermal infrared remote sensing.

The objective of this paper is to evaluate the temporal and spatial variability of stream temperatures and how stream temperatures are affected by land use through the use of airborne thermal infrared (TIR) imagery. Both five-meter and fifteen-meter MODIS/ASTER (MASTER) imagery were acquired along the main channel of the Green-Duwamish River in Washington State, U.S. in multiple straight line passes with image overlaps occurring at time intervals of between 3 and 45 min. Five- and fifteen-meter data were collected on August 25th, 2001, with a few additional five-meter images collected on August 27th. Image overlaps were studied to evaluate the time dependence between acquisition time and observed water temperature. Temperature change between adjacent images over the course of a few minutes was found to be negligible, but became significant at times greater than 45 min, with an estimated increase in water temperature of 2-3 °C between the first and last image collected for the complete five-meter resolution survey. Images captured from different days help identify persistent localized temperature differences. While accounting for temperature changes that occurred during the acquisition process, we still found that average stream reach temperatures increased with urbanization, while variability decreased. The same occurred in the immediate presence of a reservoir. This study suggests that urbanization affects stream temperature not only through the removal of riparian zone vegetation, but also through changes to sources in in-stream variability including the presence of rocks, woody debris and sandbars.

Reclaiming freshwater sustainability in the Cadillac Desert.

Increasing human appropriation of freshwater resources presents a tangible limit to the sustainability of cities, agriculture, and ecosystems in the western United States. Marc Reisner tackles this theme in his 1986 classic Cadillac Desert: The American West and Its Disappearing Water. Reisner's analysis paints a portrait of region-wide hydrologic dysfunction in the western United States, suggesting that the storage capacity of reservoirs will be impaired by sediment infilling, croplands will be rendered infertile by salt, and water scarcity will pit growing desert cities against agribusiness in the face of dwindling water resources. Here we evaluate these claims using the best available data and scientific tools. Our analysis provides strong scientific support for many of Reisner's claims, except the notion that reservoir storage is imminently threatened by sediment. More broadly, we estimate that the equivalent of nearly 76% of streamflow in the Cadillac Desert region is currently appropriated by humans, and this figure could rise to nearly 86% under a doubling of the region's population. Thus, Reisner's incisive journalism led him to the same conclusions as those rendered by copious data, modern scientific tools, and the application of a more genuine scientific method. We close with a prospectus for reclaiming freshwater sustainability in the Cadillac Desert, including a suite of recommendations for reducing region-wide human appropriation of streamflow to a target level of 60%.