Field performance evaluation and genetic integrity assessment of cryopreserved papaya clones.

This paper is the first report of field performance and evaluation of morphological traits following cryopreservation in four genotypes of Carica papaya (Z6, 97, TS2 and 35). It also describes the successful establishment of in vitro plantlets following vitrification-based cryopreservation of shoot tips and their acclimatisation through to field establishment. Cloned plants resulting from untreated controls, as well as controls taken at three other stages of the cryopreservation process (dissection, pre-treatment, plant vitrification solution 2 (PVS2) treatment) and cryopreserved plants were established to ensure a rigorous appraisal of any variation. Results indicate no differences between any of the control plants or cryopreserved plants for either growth performance or morphology. In addition, both randomly amplified DNA fingerprinting and amplified DNA methylation polymorphism markers were used to assess any genomic or methylation changes in genotype 97 at four different developmental stages post cryopreservation (in vitro, acclimatisation and field). Only small genomic DNA modifications (0-8.3%) were detected in field stage plants and methylation modifications (0-4.3%) were detected at both the in vitro and field stages for samples treated with PVS2 or cryopreservation.