Clonal seed formation by synthetic Apomixis: challenges and engineering modules for genotype fixation and cultivar maintenance

Abstract Modern breeding has benefited substantially from genetic recombination and heterosis associated with sexual reproduction. However, sexual reproduction also causes trait segregation, making elite phenotypes and complex genotypes difficult to maintain through seed. Apomixis can preserve the maternal genotype through clonal seed formation and therefore offers a potential route to fix heterosis and reduce segregation in progeny. Although apomixis has evolved independently in many angiosperm lineages, it remains largely absent from agricultural systems. Here, we discuss the ecological conditions that maintain natural apomixis and the breeding requirements that limit its application in agricultural systems. We propose that the breeding application of synthetic apomixis requires coordinated control of apomeiosis, parthenogenetic embryo initiation, endosperm compatibility, and stability and safety control. Facultative apomixis provides a useful reference for modern breeding systems because sexual reproduction can generate genetic variation, whereas apomictic seed formation can maintain selected maternal genotypes. Synthetic apomixis research is moving from studies of individual gene function toward coordinated module design, which could make clonal seed formation more feasible for agricultural breeding.