Application of gas-permeable bags for in vitro cold storage of strawberry germplasm

This study reports the first use of gaspermeable, heat-sealable polyethylene bags for cold storage of plant tissue cultures. The bags were used to develop a new cold storage system for the in vitro strawberry collection at the National Clonal Germplasm Repository (NCGR), Corvallis. In vitro Fragaria plantlets of 96 different accessions (species and cultivars) were transferred to bags with basal medium without growth regulators, heat-sealed, grown for one week at 25°C, cold hardened for one week, and then stored in the dark at 4°C. These in vitro cultures were successfully stored for up to 24 months in polyethylene bags. Evaluations at three month intervals provided information on the condition of the diverse collection. Over 75% of the accessions originally stored remained in storage for 15 months and 47% remained for over 18 months. None of the 96 accessions studied was lost due to contamination or decline in vigor. Over 300 Fragaria accessions are currently stored using this system.