Combining Ability for Winter Survival and Turf Quality Traits in St. Augustinegrass

Abstract

New elite st. augustinegrass cultivars with improved cold tolerance and desirable turf quality are needed for the turf industry, especially in the transitional climatic region of the United States. To efficiently use sources of cold tolerance in a breeding program, an understanding of the genetic control of this trait and its relationship to important turf quality traits is required. Therefore, the objective of this study was to estimate general and specific combining abilities for cold response and turf quality traits. Six diploid genotypes of st. augustinegrass were selected as parents for a diallel mating design without reciprocals and evaluated over 3 years at two locations. The true hybridity of crosses was confirmed using simple sequence repeats (SSR). Combining ability analysis revealed that both general and specific combining abilities were significant across years and locations. Specific combining ability (SCA) was the largest source of genetic variation for winter survival, genetic color, turf density, and end-of-season cover indicating that nonadditive gene effects play a key role in the inheritance of these traits. The parental genotype ‘GF2’ was identified as a promising parent for future breeding efforts as it provided positive general combining ability (GCA) effects for both cold tolerance and turf quality traits, which were not significantly correlated with one another. Lines identified as parental selfs generally showed lower cold response and inferior turf quality than the original parental lines indicating that inbreeding depression can occur in st. augustinegrass. This study provides information regarding the combining ability of cold response and turf quality traits in st. augustinegrass, which will ultimately aid in parental selection for our future breeding efforts.