Hormones and Dehydrin Expression Responses during Cold Acclimation in Two Zoysiagrass Cultivars with Contrasting Freezing Tolerance.

Zoysiagrass experiences winter-kill in many upper transition zone climates. Metabolic adustments during cold acclimation are associated with improved freezing tolerance. This study examined alterations in hormone and dehydrin expression during cold acclimation in two zoysiagrass cultivars with contrasting freezing tolerance.  Two zoysiagrass cultivars (‘Meyer’ (cold tolerant) and ‘Cavalier’ (relatively cold sensitive) were subjected to either normal growing conditions or cold acclimation treatments (8/4 ᴼC, 10 hours photoperiod, and photosynthetically active radiation at 200 µmol m^-2s^-1) for 28 days. Leaf abscisic acid (ABA) accumulated, and indole-3-acetic acid and cytokinin trans-zeatin riboside (ZR) declined during cold acclimation. Meyer had a higher level of ABA, but lower levels of cytokinins relative to Cavalier at the end of cold acclimation (day 28). In addition, cold acclimation induced dehydrin (23 kDa) expression, and Meyer had a greater abundance of dehydrin relative to Cavalier at day 28.  Meyer had less lipid peroxidation relative to Cavalier at day 28. The results of this study suggest that accumulation of ABA and a low molecular weight dehydrin during cold acclimation contributes to freezing tolerance in zoysigrass.