Diverse molecular mechanisms of in vivo haploid induction in plants: from fertilization interference to genome programming.

In vivo haploid induction has revolutionized crop breeding by shifting it from experience-driven selection to precision design methodologies. This review synthesizes three core mechanistic modules-male gamete defects (MTL/DMP/KPL), gametophyte reprogramming (BBM-BAR1), and centromere engineering (CENH3/KNL2)-into a cohesive framework and provides a critical assessment of their respective constraints. We emphasize emerging technological platforms (HIEdit, GEDH) that support transgene-free genome editing and outline advances in synthetic apomixis aimed at stabilizing hybrid vigor. Defining innovations include temperature-sensitive enhancement, synergistic mutation pyramiding, and AI-aided rational design. Persistent challenges include low efficiency in dicots, large-genome crops, and paternal haploid induction. Future research should integrate multiomics, synthetic biology, and machine learning to develop universal, cross-species haploid induction systems.