Conformity in Fruit Development of Clonal Oil Palm Conferred by Transposon Methylation

A boost of 20-30% in yield is expected when tissue culture-derived planting materials are planted and troubled by a shrinking land resource, cloning good performing palms is a well-received sustainable alternative. Cloning of elite oil palms is entrenched in breeding programmes as a way to outpace the long breeding cycle of the oil palm which generally results in slow implementation of new improved planting materials into the commercial pool. However, the emergence of a somaclonal variant known as the mantled phenotype, which drastically reduces yield, caused the industry to relook at the strategy as confidence in the cloning technology of oil palm took a nosedive. Aside from knowing that epigenetics is involved, most of the earlier research were unsuccessful in linking any markers to mantling. Through the adoption of a high-resolution epigenome technology, coupled with progress made in oil palm genome research, the team was able to pin down the cause of mantling to a B-function MADS-box gene, DEFICIENS also known as MANTLED in this context. The defect is an epigenetic mark regulated by a transposable element that causes the formation of abnormal oil palm fruit with pseudocarpels. The hypomethylation of this element, found in the intron of DEFICIENS, is common to all mantled clones along with alternative splicing and loss of small RNA. These findings will potentially lead to the development of a simple assay to allow culling of mantled nursery palms before committing limited plantation resources to clonal propagation, a boon to precision agriculture. The discovery of MANTLED will certainly fuel a much wanted growth in the oil palm clonal industry as confidence in this technology is expected to soar, thus altering the current plantation scene which relies heavily on planting materials through conventional breeding.