Salix dormant bud cryotolerance varies by taxon, harvest year, and stem‐segment length

Abstract

Willow (Salix L.) species have good qualities for becoming a biomass crop for production of biofuels. They grow on marginal soils, produce high yields of wood in a short period of time, and are easily propagated. Salix is one of the few genera that may be cryopreserved as dormant winter buds (DBs) instead of using tissue culture techniques. The objective of our study was to evaluate selected factors that affect cryotolerance of nine Salix germplasm accessions in the USDA-ARS National Plant Germplasm System collection. One-year-old branches harvested in January over 3 yr were cut into either 6-to 7-or 10-cm segments containing at least two DBs. Segments were treated with a slow-cooling procedure and stored in vapor-phase liquid N (LNV). Control segments were stored at −5 °C until planting. The LNV-exposed and the −5 °C-stored nodal segments were warmed and directly planted in a cold greenhouse. Six weeks later, the material was evaluated for shoot and root development. Segments that developed a shoot were considered viable. Average viability varied among years (0-35.1%) even for the same accession, species (4.2-51.4%), and segment length. Dormant buds on 10-cm segments had higher average viability (82.2%) than did DBs on 6-to 7-cm segments (43.9%), suggesting higher suitability for cryopreservation. In the material studied, Salix DB viability was correlated with branch diameter, DB density, and the ability to develop shoots and roots prior to cryopreservation.

Successful Cryopreservation of Dormant Buds of Blackcurrant (Ribes nigrum L.) by Using Greenhouse-Grown Plants and In Vitro Recovery

“…Moreover, a dormant bud protocol may be easier to implement compared to in vitro-based protocols, which may need considerable optimization before they can be applied in practice [39,53,54]. If the recovery of cryopreserved buds is possible by grafting or direct rooting, the whole cryopreservation process can be done without laboratory facilities [9,20]. However, if laboratory facilities are available, the recovery via in vitro offers an opportunity to revive cryopreserved material throughout the year and makes it possible to multiply plantlets via micropropagation [13].…”

“…[ 18 ]. The cryopreserved twigs of Salix can be recovered via direct rooting by placing thawed twigs in moist, sterilized soil and keeping them in high humidity until they have rooted [ 19 , 20 ]. In some temperate fruit trees, thawed twig segments can be forced, after which sprouted shoots can be excised and introduced into the tissue culture [ 21 ].…”