Breeding for apomixis in potato: Pursuing a utopian scheme

Abstract

Apomictic propagation in potato holds a great promise for the new technology of growing potatoes from botanical seeds in stead of tubers. It is explained that apomixis results from the combination of abnormal meiosis, abnormal fertilization and parthenogenesis. An ideal scheme is given for growing potatoes from true seeds. This scheme remains utopian when autonomous apomixis is not available. Autonomous apomixis occurs when the reduction division is lacking (no gene recombination, no reduction of chromosome number) and the resulting 2n egg cell develops parthenogenetically without fertilization of the central nucleus. The first best approach is pseudogamous apomixis, which differs from autonomous apomixis in the necessity of fertilization of the central nucleus. Second best is the parthenogenetic development of 2n eggs, since these have originated through an abnormal type of reduction division. This type is characterized by the lack of formation of a reduction cell wall and fusion of the two spindles at metaphase II of meiosis (first division restitution). Apomixis in the narrow sense, either pseudogamous or autonomous, is defined. It has not been found in potato species or species hybrids. On the basis of our knowledge about characteristic features of existing apomictic species, about genetics and evolution of apomixis and about the occurrence of particular elements of apomixis in potato the possibility of introducing apomixis into potato from existing elements is discussed along with methods to induce missing elements. Some tentative approaches are suggested which in the long run may lead to the detection of potato genotypes with apomictic propagation.