An Improved Cryopreservation Protocol for Mentha Spp. Based on PVS3 as the Cryoprotectant

BACKGROUND: Vitrification approaches are widely used to cryopreserve Mentha spp. genetic resources. OBJECTIVE: Here, we compared the response of 20 different Mentha species and hybrids during cryopreservation and elucidated the efficacy of two cryoprotectants. MATERIALS AND METHODS: One hundred and fifty three Mentha spp. accessions were cryopreserved using in vitro plants maintained under slow-growth storage and PVS2 or PVS3 as cryoprotectants. RESULTS: The cryoprotectant PVS2 was effective for all species, except M. requienii and M. villosanervata. The use of PVS3 increased the proportion of explants able to regrow after rewarming. The outbreak of endophytes upon rewarming was both less frequent and less severe when PVS3 replaced PVS2. CONCLUSION: Both PVS2 and PVS3 can be used as cryoprotectant for all the species and accessions of Mentha spp. surveyed. Since higher regenerations were achieved using PVS3, and since the risk of an endophyte outbreak was reduced, this cryoprotectant should be preferred in future for cryopreserving Mentha spp.