Somaclonal variation in oil palm (Elaeis guineensis Jacq.): the DNA methylation hypothesis

The occurrence of somaclonal variants (ca 5%) among populations of somatic embryo-derived oil palms (Elaeis guineensis Jacq.) currently hampers the sc aling-up of clonal plant production. In order to investigate the relationsh ip between the ''mantled' somaclonal variant and possible alterations in ge nomic DNA methylation rate, two complementary approaches have been used. HP LC quantification of relative amounts of 5-methyl-deoxycytidine has shown t hat global methylation in leaf DNA of abnormal regenerants is 0.5-2.5% lowe r than in their normal counterparts (20.8% vs 22%, respectively). When comp aring nodular compact calli and fast growing calli, yielding respectively 5 % and 100% of "mantled'' plantlets, this decrease was up to 4.5% (from 23.2 to 18.7%). An alternative method, the SssI-methylase accepting assay, base d on the enzymatic saturation of CG sites with methyl groups, gave converge nt results. This work demonstrates that a correlation exists between DNA hy pomethylation and the ''mantled" somaclonal variation in oil palm.