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 ex- plants, 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 guineen- sis Jacq.) calli was performed, with the aim to identifying chromosome instability as a possible cause of soma- clonal 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 dem- onstrated 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 gamete- like state, including chromosomes segregation and the occurrence of haploid gamete-like cells. The intrinsic instability of oil palm chromosomes was also verifi ed.