Inheritance of cold tolerance in St. Augustinegrass

St. Augustinegrass [Stenotaphrum secundatum (Walt.) Kuntze] is a popular southern turfgrass with poor cold tolerance. The objective of this study was to evaluate the inheritance of cold tolerance in St. Augustinegrass, Eight diploid genotypes were chosen as parents for a complete diallel mating with reciprocals. Three replications of each single cross and the parents were planted in a field trial at Mississippi State, MS, and winter survival was evaluated from 1994 to 1996. Differential thermal analysis was used to predict lethal low temperatures for parents and single cross progenies. Lethal temperatures of parental genotypes ranged from -3.65 to -5.25 degrees C. Combining ability analysis revealed that general combining ability was the largest source of variation for lethal temperature and winter survival. Specific combining ability was significant only for winter survival in 1996. Reciprocal effects were significant for winter survival each year. Estimated narrow sense heritability was 0.58 for lethal temperature and ranged from 0.70 to 0.98 for winter survival. Lethal temperatures were significantly correlated to winter survival of each year.