Cold hardiness in bermudagrass cultivars as affected by the sequential trinexapac-ethyl application during growing season

Abstract: Bermudagrass turfs are widely used in subtropical to tropical regions and in transition zones for golf courses, landscape areas, and athletic fields. Lack of adequate cold tolerance in these grasses causes early winter dormancy and an aesthetically unpleasing surface. This study investigated the effect of sequential Trinexapac-ethyl (TE) applications during the growing season on fall color retention, spring green-up, and physiological responses related to cold hardiness in bermudagrass cultivars. Trinexapac-ethyl (untreated, 6.0, 12.0, and 18.0 mg a.i. m^-2) was applied monthly throughout the bermudagrass growing season. According to the results, TE applications enhanced spring green-up and possessed color retention for 20 and 12 days longer in the first and second years of the study, respectively. Higher proline and total carbohydrate contents were observed in the crown of TE-treated as compared to untreated turfs. Hybrid cultivars exhibited higher spring green-up, rhizome survival, proline content, total carbohydrates, and longer color retention than seeded cultivars. The higher proline content of the crown was positively associated with enhanced color retention, rhizome survival, and spring green-up. Finally, these results confirmed that accumulated osmolytes in the crown (resulting from growing-season TE application) minimized the dormancy period in winter via improvement of fall color retention and spring green-up.