Haploid induction mechanisms and applications in plant breeding: Roles of CENH3, PLA, and DMP and their integration with apomixis

Recent advances in haploid induction technologies have created new opportunities to accelerate crop breeding and achieve rapid genotype fixation.Three major haploid induction systems, CENH3, MTL/NLD/ZmPLA1, and DMP-mediated approaches, have each demonstrated the capacity to induce haploids across diverse plant species.Although each system operates through distinct molecular mechanisms, all enable the production of haploid embryos that can subsequently be chromosome-doubled to obtain fully homozygous lines within a single generation.Concurrently, the development of the MiMe (Mitosis Instead of Meiosis) system, which replaces meiosis with mitosis, has enabled the formation of clonal gametes genetically identical to the parent.Integrating haploid induction with MiMe technology provides a promising route to achieve synthetic apomixisan innovative breeding strategy that mimics asexual reproduction in normally sexually-reproducing plants.Synthetic apomixis enables the production of clonal seeds that faithfully preserve the parental genotype, thereby maintaining heterosis across generations.This approach has the potential to revolutionize hybrid seed production by eliminating the need for repeated crossing, thereby shortening breeding cycles and reducing associated costs.However, despite promising outcomes in certain plant species, significant challenges remain, including low haploid induction efficiency, reduced seed set, and an incomplete understanding of the molecular mechanisms underlying this system.In this review, we discuss these challenges and highlight future directions for achieving robust and efficient synthetic apomixis in crops.