St. Augustinegrass is a warm-season grass species widely utilized as turf in the southeastern U.S. It shows significant variation in plant growth and morphological characteristics, some of which are potentially associated with drought tolerance. However, the genetic basis of these variations is not well understood. Detecting quantitative trait loci (QTL) associated with morphological traits will provide a foundation for the application of genetic and molecular breeding in St. Augustinegrass. In this study, we report QTL associated with morphological traits, including leaf blade width (LW), leaf blade length (LL), canopy density (CD), and shoot growth orientation (SGO) in a St. Augustinegrass ‘Raleigh’ x ‘Seville’ mapping population containing 115 F1 hybrids. Phenotypic data were collected from one greenhouse and two field trials. Single and joint trial analyses were performed, finding significant phenotypic variance among the hybrids for all traits. Interval mapping (IM) and multiple QTL method (MQM) analysis detected seven QTL for CD, four for LL, five for LW, and two for SGO, which were distributed on linkage groups RLG1, RLG9, SLG3, SLG7, SLG8 and SLG9. In addition, three genomic regions where QTL colocalized were identified on Raleigh LG1 and Seville LG3. One genomic region on Seville LG3 overlapped with two previously reported drought-related QTL for leaf relative water content (RWC) and percent green cover (GC). Several candidate genes related to plant development and drought stress response were identified within QTL intervals. The QTL identified in this study represent a first step in identifying genes controlling morphological traits that might accelerate progress in selection of St. Augustinegrass lines with lower water usage.

Shallow waterbodies are abundant in many landscapes across the globe and are increasingly acknowledged for their role in freshwater C cycling. This study investigated organic-matter decomposition potentials in flocculent organic sediment, a rarely-investigated sediment type commonly found in shallow waters. Further, this study investigated how porewater chemistry and temperature affect decomposition rates within flocculent sediment. We quantified decomposition rates during 3 seasons by deploying a standardized substrate (cotton strips) within and above the flocculent sediment layer in the littoral zones of lakes, shallow through-flow wetlands, and depositional zones on the margins of stream channels of southwestern Michigan, USA. We then compared our results with those reported for other freshwater settings that used the same cotton-strip assay. There was high accumulation of organic matter in the shallow waterbodies, but decomposition rates in flocculent sediments averaged 1.7Â greater than rates measured in oxic overlying waters and were generally only eclipsed by temperatureadjusted rates reported in streams, which are typically well-oxygenated, flowing environments. Rates were positively correlated with sediment porewater concentrations of soluble reactive P and dissolved iron and negatively correlated with ammonium. Warmer temperatures also resulted in increased decomposition rates, and the temperature sensitivity results suggest that decomposition rates in flocculent sediments could increase 11 to 52% with a 1 to 47C increase in water temperatures, a realistic range of increase for this region in the next 100 y if climate change continues at the current pace. Thus, high organic matter inputs, rather than slow decomposition, must lead to the development of flocculent organic sediments. Future warming could therefore increase decomposition rates and tip the balance toward net losses of organic matter.