Abstract Apomixis is an asexual mode of reproduction through seeds and nearly all gametophytic apomictic species are polyploid. Psidium cattleyanum, a polyploid species with several described ploidy levels, exhibits apomixis and requires effective pollination for fruiting (pseudogamy). The aim of this study was to determine the frequency of apomixis and sexuality in heptaploid and octoploid accessions of P. cattleyanum, and to analyse maternal and paternal contributions to endosperm formation. Flow cytometry was used on mature seeds obtained from hand-pollinated crosses between two octoploid and two heptaploid accessions to determine the ploidy levels of embryo and endosperm. Among the 492 seeds analysed, embryo: endosperm ploidy ratios ranged from the expected 2:5 (64.2%, pseudogamous apomixis) and 2:3 (4.7%, sexuality) to unexpected values including 1:3 (0.4%), 2:6 (2.4%), 2:7 (0.2%), 3:5 (8.8%), 2:3:5 (18.5%), and 2:4:6 (0.8%), associated with polyhaploid parthenogenesis, pseudogamous apomixis involving reduced and unreduced gametophytes, and female gametophytes with two or three polar nuclei. Embryos with both higher and lower ploidy than the maternal plant were detected, and the implications of these findings for wild populations are discussed.
Luz-Graña et al. (Wed,) studied this question.