LONG-TERM STORAGE OF HAZELNUT EMBRYONIC AXES IN LIQUID NITROGEN

Abstract

Whole hazelnut (Corylus L.) seeds do not survive freezing in liquid nitrogen (LN2) because of large size and high oil content. However, excised embryonic axes can survive with appropriate treatment. Although freshly harvested axes are easily cryopreserved, secondary donnancy inhibits growth soon after harvest. A short stratification treatment of stored nuts followed by dehydration and LN2 storage was successful for long-term storage of hazelnut gennplasm. Whole seeds dried to very low moisture contents were frozen and the embryonic axes survived LN2 exposure although cotyledons were badly damaged. Dried whole hazelnuts can be stored in LN2 if the axes are excised and cultured after thawing. This technique avoids the problems of cotyledon damage and subsequent contamination and death of whole seeds during gennination. A two-week stratification of stored seed before excision of axes greatly improved shoot growth and decreased callusing. Drying isolated embryonic axes to 8-10% moisture, either by laminar flow or over silica gel prior to freezing, produced high survival and shoot growth from stratified-stored Corylus seed. C. americana Marshall, C. colurna L., C. heterophylla Fisch. Ex Trautv., and C. sieboldiana ~lume axes were prepared, cryopreserved, shipped to the National Seed Storage Laboratory In Fort Collins, Colorado, and stored in liquid nitrogen. This is the first base (long-tenn) conservation of hazelnuts in world germplasm collections. Seed of additional species will be added as they become available.