Can mimicking sexual reproduction solve problems with recalcitrance in in vitro propagation of tree species?

Abstract

Clonal propagation by in vitro means of adult forest trees is often difficult or not possible with current technology. This problem, generally described as recalcitrance, has been approached from several angles by researchers and reviewers. However, it has not yet been reviewed from the point of view that it may eventually be possible to overcome recalcitrance by mimicking the rejuvenation process that occurs during sexual reproduction. It is suggested that somatic cell nuclear transfer, in a manner similar to the one used for animal cloning, could be helpful. Furthermore, application of controlled stress and autophagy, or inducing apomixes by halting natural or artificially induced meiosis before chromosome segregation, could perhaps assist in overcoming recalcitrance. The discussion below indicates that mimicking the sexual or apomictic process in vitro is worthy of further exploration and should be evaluated as a means of genetically improving tree species, especially those of high economic value. Studies along these lines may also be helpful in improving our knowledge of the epigenetic, cytogenetic, and genomic mechanisms involved.