Abstract
The number of species conserved by cryopreservation is increasing thanks to the development of robust vitrification-based protocols. Managing oxidative stress is critical for the successful application of cryopreservation to plant tissues. This research was aimed at understanding the protective effect of pre-treatment of stock plantlets with cold, and their shoot tips with sucrose and an antioxidant (ascorbate) during cryopreservation by droplet vitrification (DV). The levels of enzymatic and non-enzymatic oxidative markers as well as oxidative damage in pre-treated and untreated shoot tips of Actinidia chinensis var. chinensis Hort16A' at different stages of DV and recovery were studied. All the antioxidant markers showed a significant increase in shoot tips from cold-acclimated plantlets pre-treated with a combination of sucrose and ascorbate compared with untreated shoot tips throughout the steps, especially 24h after recovery from cryopreservation. Oxidative damage markers; lipid peroxides and protein carbonyls were significantly lower in pre-treated shoot tips than in untreated shoot tips after cryopreservation, suggesting better protection as a result of the pre-treatments used. These observations were confirmed in recovery studies where shoot tips that were harvested from cold-hardened plantlets, and pre-treated with sucrose and ascorbate, showed 40% regeneration against 0% in cryopreserved shoot tips that were not pre-treated. Key messageCombined pre-treatments with cold, sucrose and ascorbate enhance antioxidant metabolism and improve survival of cryopreserved kiwifruit shoot tips.