Cytological and Molecular Genetic Analysis of Polyembryony in an Apricot × Almond Interspecific Hybrid Cultivar

Polyembryony holds great potential for heterosis fixation and germplasm innovation in plant breeding. This study elucidated the origin and cytogenetic basis of polyembryony in ‘Jingren 4’, which is an interspecific hybrid cultivar of apricot × almond (Prunus armeniaca L. × Prunus dulcis (Mill.) D. A. Webb) with high-frequency double kernels and polyembryonic kernels. Embryological observation, flow cytometry, karyotyping, SSR genotyping and nutrient analysis were conducted, and polyembryony rates were evaluated in seven hybrid lines from four cross combinations. Polyembryos in ‘Jingren 4’ initiated early after pollination and developed stably without abortion, while occasional twin embryos in monoembryonic kernel-using apricot cultivar ‘Yiwofeng’ (Prunus armeniaca L.) aborted at later stages. SSR confirmed identical genotypes in seedlings from one polyembryonic kernel (zygotic cleavage origin), whereas double-kernel seedlings had distinct genotypes. All progeny was diploid (2n = 2x = 16), but polyembryonic seedlings showed a more symmetrical 2A karyotype. Double-kernel stones (68%) and polyembryonic kernel stones (9%) significantly increase the kernel recovery rate and the number of seedlings; embryo number markedly affected single embryo mass and seedling vigor, with minor differences in nutrient contents. Hybrid polyembryony rates ranged 3.33–40.00%, showing strong genotype dependence. These findings support polyembryony application in apricot heterosis fixation and clonal rootstock breeding.