Exposure of pineapple shoot tips to liquid nitrogen and cryostorage do not affect the histological status of regenerated plantlets

Conservation of pineapple (Ananas comosus L. Merr.) genetic resources - including cryopreservation in liquid N-2 at -196 degrees C - is essential for future breeding programmes to develop new varieties with improved agronomic performance. However, the potentially deleterious effects of cryopreservation on subsequent plant regrowth should be evaluated before large-scale development of cryobanks is implemented. This paper describes the histological analysis of pineapple plantlets regenerated from cryopreserved shoot tips. Two controls were included in the study: i) conventional micropropagation-derived plantlets, and ii) plants from shoot tips subjected to pre-cryostorage conditioning treatments but never exposed to liquid N-2. Histological studies of roots, leaves and stems were conducted after 45 days of hardening. No statistically significant differences with the controls were observed in any of the histological parameters evaluated, which supports the practical value of cryopreservation of pineapple germplasm.