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Title: Freeze-Testing in St. Augustinegrass II: Evaluation of acclimation effects

Author
item KIMBALL, JENNIFER - North Carolina State University
item Tuong, Tan
item ARELLANO, CONSUELO - North Carolina State University
item Livingston, David
item MILLA-LEWIS, SUSANA - North Carolina State University

Submitted to: European Journal of Agronomy
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/8/2017
Publication Date: 6/20/2017
Citation: Kimball, J., Tuong, T.D., Arellano, C., Livingston, D.P., Milla-Lewis, S.R. 2017. Freeze-Testing in St. Augustinegrass II: Evaluation of acclimation effects. European Journal of Agronomy. 213:282-286.

Interpretive Summary: St Augustinegrass is a common choice for homeowners lawns in southern parts of the US because of its excellent drought and shade tolerance. However, its ability to resist freezing tolerance is very poor. A better understanding of how this important species acclimates in the fall by using innovative ways to evaluate survival after freezing could help make this species a viable option in more northerly areas. In this study various methods of growing, freezing, and evaluating recovery from freezeing were investigated. Differences between 9 genotypes for the degree of green up after thawing was determined using digital images. This study showed that a variety of data collection methods can aid breeders in selecting germplasm to improve the winterhardiness of St Augustinegrass.

Technical Abstract: Winter survivability is a major-limiting factor for St. Augustinegrass (Stenotaphrum secundatum [Walt.] Kuntze) grown in the transition zone of the United States as cold winters can result in high levels of winterkill. In addition to field studies, lab-based freeze tests mimicking field winter survivability can contribute to the selection of cold hardy lines and ultimately, aid in breeding for cold tolerance. This study used a whole-container freeze method to evaluate four freezing temperatures and two data collection systems in freeze tests of nine St. Augustinegrass genotypes ranging in their winter survivability. Results indicated -3°C and -4°C to be more suitable temperatures for evaluating freeze survival in St. Augustinegrass using this methodology than -5°C and -6°C. Weekly visual ratings of surviving green tissue and regrowth were correlated with one another over a six week evaluation period post-freeze. The length of post-freeze evaluation for these different rating systems was also assessed and determined to vary depending upon the rating system. Additionally, we provide evidence that digital imaging techniques commonly utilized in turfgrass field studies are also useful in estimating surviving green tissue and regrowth in lab-based freeze tests. Percent green cover calculated using digital images was highly correlated with visual ratings for all ratings taken 2, 4, and 6 weeks post-freeze. This study provides unique information regarding freezing temperatures, genotype responses, and data collection methods in St. Augustinegrass, which should aid breeders in the improvement of freezing survival in this species.