Low temperature storage of Fragaria sp. and Pyrus sp. genetic resources in vitro.

Climatic conditions, plant diseases and pests constitute a serious hazard to genetic resources maintained in field collections. In vitro culture techniques, including storage under growth limiting conditions and cryopreservation, provide storage alternatives for protecting valuable germplasm. The objectives of present study were to develop a procedure for in vitro low temperature storage of strawberry and pear and to investigate the effect of different culture media and incubation duration at low temperature on the state of plants of various genotypes. In vitro stored twenty strawberry and nine pear accessions were used for the study at the Institute of Horticulture, Lithuanian Research Centre for Agriculture and Forestry (LRCAF) during 2009-2011. After a 15-month in vitro storage at 4 degrees C temperature, 40% of strawberry plants were in good condition (average rating point exceeded 2), 60% of plants in poor and bad condition (average rating point below 2). Character of change of plant condition during storage was genotype dependent but was not associated with new shoot and leaf formation. The condition of Fragaria x ananassa 'Catskill', 'Nida', 'Melody', 'Venta' and F virginiana after storage was the best, while that of F. x ananassa 'Suvetar', 'Jasna', 'Elsanta', 'Saulene' and F virginiana glauca, F vesca was the worst. Pear microshoots were stored successfully at 4 degrees C temperature for 6 months in vitro on MS (Murashige and Skoog) growing medium with 3% sucrose with or without benzylaminopurin (BAP) addition depending on the genotype. Addition of 2% mannitol to the storage medium did not improve microshoots condition during the low temperature storage.