Oil palm in vitro regeneration: microdensitometric analysis during reproduction and development

An extensive microdensitometric analysis was performed in oil palm Elaeis guineensis Jacq. during the establishment of a new embryogenic culture, on new regenerated plants at different times, and finally on seedlings obtained from adult regenerated normal and abnormal plants. Moreover nuclear DNA content was determined as well during the progression of meiosis. A variable loss of DNA content/nucleus in regenerated plants was demonstrated, in some cases very severe, depending mainly on the in vitro stationing of explants before the regeneration induction; DNA variation, but to less extent, was recorded also in seedlings from adult mother plants of the same genotype, in vivo and in vitro propagated. Considering normal and abnormal regenerated plants, DNA content variations did not seem to be necessarily connected to the abnormal phenotype. In addition stable and different variants in genome size could be obtained from in vitro culture of the same explant. Changes in the values of nuclear DNA content were determined during the meiotic prophase, confirming DNA extrusion processes also observed in other plant systems in vivo. Indeed the regeneration process may induce a quantitative DNA modulation/loss per cell in the regenerated plants but progressively DNA sequences should be regained before completion of the meiotic process. This information points to mechanisms of somaclonal variation.