AbstractPseudogamous apomixis inPaspalum simplexgenerates seeds with embryos genetically identical to the mother plant and endosperms deviating from the canonical 2(maternal):1(paternal) parental genome contribution into a maternal excess 4m:1p genome ratio. InP. simplex, the gene homologous to that coding for subunit 3 of theORIGIN OF RECOGNITION COMPLEX(PsORC3) exists in three isogenic forms:PsORC3ais apomixis specific and constitutively expressed in developing endosperm whereasPsORCbandPsORCcare up-regulated in sexual endosperms and silenced in apomictic ones. This raises the question of how the different arrangement and expression profiles of these threeORC3isogenes are linked to seed development in interploidy crosses generating maternal excess endosperms. We demonstrate that down-regulation ofPsORC3bin sexual tetraploid plants is sufficient to restore seed fertility in interploidy 4n×2ncrosses and, in turn, its expression level at the transition from proliferating to endoreduplication endosperm developmental stages dictates the fate of these seeds. Furthermore, we show that only when being maternally inherited canPsORC3cup-regulatePsORC3b. Our findings lay the basis for an innovative route—based onORC3manipulation—to introgress the apomictic trait into sexual crops and overcome the fertilization barriers in interploidy crosses.