Genetic integrity assessment of cryopreserved tomato (Lycopersicon esculentum Mill.) genotypes

Shoot tips of five tomato (Lycopersicon esculentum Mill.) genotypes were successfully cryopreserved by droplet vitrification. Recovered plants were studied for genetic stability by two different assays: amplified fragment length polymorphism (AFLP) using 4 primer combinations and sequencing of lycopene β-cyclase gene (LCY-B) from leaves. The highest shoot regeneration after cryopreservation was 70% (Pontica) following 24 h osmoprotection in 0.5 M sucrose and 30 min dehydration in plant vitrification solution 2 (PVS2). The data inferred from AFLP showed no genetic dissimilarities between in vitro regenerants derived from cryopreserved tissues compared with the noncryopreserved controls. Although a single nucleotide polymorphism, a G→T transversion, was identified in position 1139 in Capriciu and Darsirius, this was not due to the cryopreservation process itself, since it was detected in both cryopreserved and control samples. Thus, sequencing of LCY-B gene from leaves revealed no DNA damages after cryopreservation and subsequent in vitro regeneration. Our results indicate that cryostorage by droplet vitrification is an efficient and reliable technique to preserve the selected tomato genotypes and to regenerate true-to-type plants.