Pollen grain performance in Psidium cattleyanum (Myrtaceae): a pseudogamous polyploid species

Abstract

In apomictic pseudogamous reproduction, the asexual embryo requires a sexual origin of the endosperm for its nutrition; hence, fertilization is necessary for seed development to occur. Male gametophyte functionality in apomictic polyploids is highly variable and often linked to low values of pollen grain viability. This work evaluates pollen grain development and functional attributes in Psidium cattleyanum, a polyploid and apomictic pseudogamic species. We consider pollen grain ontogeny and pollen grain morphology, size, and viability in two ploidy levels, octoploid and heptaploid. Plants with different ploidy levels showed variation in the duration of microsporogenesis and the size of microspores. Microsporogenesis exhibited several abnormalities in all studied plants, but more frequently in heptaploids; cytomixis was detected in meiosis. Psidium cattleyanum pollen grains registered morphotypes typical of the Myrtaceae family and other heteropolar forms that were not previously described for the genus. Pollen grain size was heterogeneous but larger in octoploid plants. Pollen viability was low and varied both intra- and between ploidies; pollen morphotypes contribute differently to pollen viability depending on the ploidy of the plant. Several abnormalities detected during pollen grain ontogeny affect pollen grains performance. Polyploidy is proposed as the leading cause of meiosis abnormalities. Further, variations in pollen grain viability and final pollen size and morphology found in different plants suggest that ploidy levels can affect these attributes differently.