|dc.description.abstract||This paper presents the development of cryopreservation protocols for zygotic embryos and
apices of chayote (Sechium edule Jacq. Sw.), a tropical plant species with recalcitrant seeds.
Zygotic embryos of two cultivars, Ccocro negro (CN) and Claudio (Cl) could withstand
cryopreservation, with survival percentages of 10 and 30 %, after desiccation to 23 and 19 %
moisture content (fresh weight basis), respectively. Apices sampled on in vitro plantlets of
cultivars Cl, 13 and JM were successfully cryopreserved using a vitrification technique.
Optimal conditions included the culture of mother-plants for 22 days on medium containing
0.3 M sucrose, culture of excised apices on the same medium for 1 day, loading of apices for
20 min with 2M glycerol + 0.4M glycerol, treatment with a series of diluted PVS2 solution
(60 % PVS2 followed by 80 % PVS2 solution for 15 min (cultivar Cocoro Blanco [CB]) or 30
min (cultivars CN and Cl) at each concentration), rapid freezing and thawing, washing of
shoot-tips with a 1.2 M sucrose solution, followed by recovery on media with progressively
decreasing sucrose concentrations until the standard concentration of 0.1 M was reached. The
highest survival percentages achieved ranged between 17 and 38 %, depending on the