CRYOPRESERVATION OF NATIVE KAZAKHSTAN APRICOT(PR UN US ARMENIA CA L) SEEDS AND EMBRYONIC AXES

摘要

BACKGROUND: Preserving the genetic diversity of Central Asia includes conserving wild apricots found in the foothills of several mountain ranges. These include primitive and genetically diverse populations with important characteristics for crop improvement. Apricot seeds have a short storage life, so cryopreservation of the seeds of wild populations is important for conserving the genetic diversity. OBJECTIVE: This study was to determine a suitable protocol for long-term storage. METHODS: This study tested a range of protocols using embryos and embryonic axes for storage of an important population of wild apricots and to determine if seed size and the distribution of moisture in the seed play a role in successful cryopreservation. RESULTS: Germination of scarified whole seed from trees in the 'Jungar' population of Prunus armeniaca varied from 63% to 90% after 1 h in liquid nitrogen (LN) and was generally better at 7% moisture content (MC) than at the original 14% MC. Embryos (4% MC) from stratified seed had only 33% germination after LN exposure. Isolated embryonic axes from non-stratified seed germinated at 86% to 100% following drying to 4% or 7% MC. Examination of three seed sizes determined that the MC of whole seed, embryos and isolated axes varied with the seed size and shape. MC of whole seeds and embryos decreased as size decreased, however, the axis MC did not. MC of medium-size seed was more evenly distributed between the axis and endosperm than in the larger or smaller samples. Cryopreservation of axes from medium-sized seed was good at any moisture content and a 1-h drying time was significantly better than 90 min. for axes of all seed sizes. Cryopreservation of axes using vitrification protocols initially designed for shoot tips produced germination similar to or lower than seed and axis drying techniques. CONCLUSION: We recommend storing apricot germplasm as unstratified seed dried to 7% MC or as isolated embryonic axes.