Cytogenetic and histological approach for early detection of “mantled” somaclonal variants of oil palm regenerated by somatic embryogenesis: first results on the characterization of regeneration system.

The occurrence of anomalous cytological events during the cell proliferation of plant primary explants, and the prevalence of polyploidization and chromosome reduction events, mainly induced by in vitro culture stress, generate large genome variability among cultured committed cells and successively regenerated plants. A thorough cytological analysis on different embryogenic and non-embryogenic oil palm (Elaeis guineensis Jacq.) calli was performed, with the aim to identifying chromosome instability as a possible cause of somaclonal variants in the regenerated plants. Besides, the process of embryoids formation from embryogenic calli was dissected, setting up a fast and reliable system of tissue culture from zygotic embryos. Our results demonstrated that in the cultured explants of oil palm, similarly to other plant species, the initial events leading to embryogenic/regeneration commitment were managed by a reprogramming of somatic cells towards a gametelike state, including chromosomes segregation and the occurrence of haploid gamete-like cells. The intrinsic instability of oil palm chromosomes was also verified.