Genotype By Environment Interaction in Cynodon Germplasm for Biomass Yield across the Southeastern USA.

Bermudagrass (Cynodon spp. L.) is the most important warm-season perennial grass grown for forage and turf in the Southeastern USA. Plant introductions (PI’s) are valuable genetic resources for cultivar development. A world collection of Cynodon species is available at the National Plant Germplasm System (NPGS). The objective of this study was to calculate genetic parameters in a set of 287 bermudagrass genotypes for biomass yield across five locations across the southeastern USA (Citra and Marianna, FL; Tifton, GA; Ardmore, OK; and Jackson Springs, NC) and multiple harvests/years. The population was composed of: i) 146 PI’s from the bermudagrass core collection maintained at Tifton, GA; ii) 137 PI’s from the NPGS maintained at Griffin, GA; and iii) commercial cultivars (“Tifton 85”, “Coastal”, “Jiggs”, and “Florida 44”). The experiment was designed as a row-column with two replicates and augmented representation of the cultivars. Experimental units were established in the summer 2014 (summer 2015 in Ardmore). Dry biomass yield (kg/ha) was assessed in each location starting the year after establishment, and multiple harvests were performed in each site: 2 (Ardmore, Jackson Springs, and Marianna), 8 (Tifton) and 11 (Citra). Linear mixed models with repeated measures (harvests) were implemented in ASReml to estimate variance components and calculate genetic parameters. Broad sense heritability (H²) for forage yield ranged from 0.08 to 0.54 for analyses performed by location, while H²=0.09 for the multi-location model. Genotype by environment correlation (r_B) ranged from 0.73 to 0.91 for analyses by location, indicating stable genotypic performance for forage yield across harvests within locations; while the low correlation (r_B=0.26) for the multi-location model shows that genotypes performed differently across locations. Our results exhibit the importance of breeding bermudagrass varieties adapted to specific sites across the southeastern USA.