Evaluating Freeze Tolerance of Bermudagrass in a Controlled Environment

Abstract

Freeze tolerance is an important characteristic in bermudagrass [Cynodon dactylon (L.) Pers. × C. transvaalensis Burt-Davy] bred for the geographic transition zone between warmand cool-season turfgrasses. Field-grown turf has been sampled and exposed to controlled freezing and viability testing to evaluate relative hardiness of cool-season grasses (Gusta et al., 1980), St. Augustinegrass [Stenotaphrum secundatum (Walt.) Kuntze] (Fry et al., 1991), and bermudagrass (Anderson et al., 1988). However, acclimation of field-grown plants is not reproducible and is subject to seasonal constraints. Cold hardening of cool-season grasses has been reported following acclimation in controlled environment chambers at 5 and 0C (Rajashekar et al., 1983). Our objectives were to develop procedures to evaluate freeze tolerance of bermudagrass genotypes acclimated under controlled conditions and to screen large numbers of genotypes for superior freeze tolerance. Relative hardiness levels. Clonally propagated plants of ‘Tifgreen’, ‘Tifton 10’, ‘Midfield’, ‘Vamont’, ‘Midlawn’, and ‘Midiron’ were grown from sprigs in 0.16liter “cone-tainers” (Ray Leach Cone-miner Nursery, Canby, Ore.) in a greenhouse maintained above 22C for at least 6 weeks. A medium containing 3 peat : 2 sand : 2 vermiculite (by volume) was amended with fritted trace elements. While growing in the greenhouse, plants were fertilized at each watering with 300 mg 20N-9P-17K soluble fertilizer/ liter (Peters Professional, W.R. Grace & Co., Fogelsville, Pa.). No fertilizer was applied during acclimation. Plants were transferred from the greenhouse to a controlled-environment chamber (model PGW36; Conviron, Asheville, N.C.) and set at 8/2C day/night