Freeze tolerance of forage bermudagrasses

The ability to survive harsh winters is one of the primary factors limiting bermudagrass (Cynodon spp.) distribution, especially those used for forage. Consequently, improved stress tolerance has been a goal of programmes for breeding bermudagrasses. While significant progress has been made in developing and evaluating freeze tolerance of turfgrasses, information on forage bermudagrasses is limited. Our objective was to evaluate freeze tolerance of recently released forage bermudagrasses compared with standard cultivars. Plants were established and acclimated in growth chambers and exposed to sub-freezing temperatures in a programmable freeze chamber. Plant responses to low-temperature exposures were quantified by regrowth mass. Freeze tolerance of Tifton 44 and Coastal was not significantly different from Midland, the reference cultivar. Coastcross, Tifton 85 and Tifton 68 were more susceptible to low-temperature injury than Midland, while Hardie, Goodwell, Midland 99 and Ozark were more freeze tolerant than Midland. Ozark, Midland 99, Goodwell and Hardie are less likely to sustain winterkill than Coastcross, Tifton 85 and Tifton 68 in areas that frequently experience low temperatures. Cultivars with one or more parents originating in Kenya had poor freeze tolerance, while germplasm from Yugoslavia and Afghanistan produced plants that were more freeze tolerant.