Cold acclimation improves recovery of cryopreserved grass (Zoysia and Lolium sp.)

Cold acclimation of Lolium L. and Zoysia Willd. grass cultivars significant ly increased regrowth of cryopreserved meristems. One wk of cold acclimatio n improved recovery following cryopreservation but extended cold acclimatio n (4-8 wk) resulted in the best regrowth. Cold acclimation also significant ly increased the dehydration tolerance of both Zoysia and Lolium meristems. Lolium apices cold acclimated for 4 wk produced 60-100% regrowth following cryopreservation by slow freezing or encapsulation-dehydration. Cold-accli mated Zoysia had greater than 60% regrowth following encapsulation-dehydrat ion when beads were dehydrated to less than 22% water content. Non-acclimat ed meristems of both genera had little or no regrowth. Thawed meristems gre w quickly without callus formation and the plantlets produced were transpla nted to pots in the greenhouse after 4 to 6 wk. Samples of each cultivar we re stored in liquid nitrogen as part of the U.S. National Plant Germplasm S ystem.