Seed cryopreservation of Corymbia citriodora: effects of cryoprotective treatments on seed vigor and germination

Abstract

Efficient ex situ conservation of forest genetic resources depends on protocols that preserve seed viability during ultra-low-temperature storage. This study evaluated the effects of cryoprotective solutions on the germination and vigor of Corymbia citriodora (Hook.) K.D. Hill & L.A.S. Johnson seeds after storage in liquid nitrogen (-196 °C). A completely randomized design was used with six cryoprotective treatments and four replicates of 25 seeds each. Seeds were packed in cryotubes and subjected to the following treatments: control, 0.4 mol L−1 sucrose, 2.0 mol L−1 glycerol, PVS1, PVS2, and PVS3 before storage in liquid nitrogen (-196 °C). After 70 days of storage, the seeds were thawed at 40 °C for 1 min and tested for germination on Germitest paper under controlled conditions. Initial vigor, final germination, abnormal seedlings, and hard seeds were assessed. Data were analyzed by analysis of variance, Tukey's test, generalized linear models with binomial distribution, principal component analysis, and hierarchical clustering. Initial vigor did not differ among treatments; however, final germination declined in the sucrose, glycerol, and PVS3 treatments. PVS1 performed similarly to the control and showed the best overall post-thaw response. These results indicate that less aggressive vitrification solutions are more suitable for maintaining the viability of C. citriodora seeds under cryogenic storage.