Freezing Tolerance of Selected Zoysiagrass Lines in Controlled Environmental Conditions.

Winter-hardiness of zoysiagrass (Zoysia spp.) is an important trait that influences its geographical adaptation in the transition zone. The objective of this study was to evaluate the freezing tolerance (LT50) of nine selected zoysiagrass lines (DALZ 1301 to DALZ 1309) in comparison to Z. japonica cv. Meyer in controlled environmental conditions. DALZ 1301 to DALZ 1309 represent selections of Z. matrella, Z. japonica and interspecific hybrids between Z. matrella with Z. pauciflora and Z. minima. Plants were propagated in 60 ml cone-tainers and acclimated at 8/2 °C (day/night) for 4 wk in the growth chamber for two separate experiments. After acclimation, plants were subjected to freezing treatments from -3°C to -13°C and placed in the greenhouse maintained under optimal growing conditions for recovery. The plugs were visually rated for green-up during recovery on a 1 to 9 scale. Nonlinear regression analysis was used to calculate the LT50 value for each line. Lethal temperature treatments resulting in 50% survival (LT50) scored after 5 wk in the greenhouse ranged from -1.4°C for DALZ 1303 to -10.6 °C for DALZ 1301 (Z. matrella). Meyer and DALZ 1301 had significantly superior freezing tolerance than DALZ 1302 to DALZ 1309 in experiment 1. Meyer has been the standard among zoysiagrasses for cold hardiness in the transition zone. Our initial results show that DALZ 1301 has similar freezing tolerance to Meyer but with finer leaf texture. The experiment 2 is underway and results from both experiments will be presented.