Ploidy level selection during germination and early stages of seedling growth in the progeny of allohexaploid facultative apomict,Hieracium rubrum (Asteraceae)

Selection within progeny of a facultative apomict,Hieracium rubrum, was studied using flow cytometry of embryos in seeds (a modified method of Flow Cytometric Seed Screen) and seedlings. Flow cytometric screening of particular progeny classes was based on distinct ploidy categories, reflecting the way of their origin. The results of both estimations of progeny composition significantly differed, which makes direct comparison of proportions detected in seeds or seedling stage impossible. The results suggest that progeny originating from reduced egg cells have higher mortality during germination and the early establishment phase than that from unreduced egg cells. Within the progeny of emasculated plants, the proportion of polyhaploid progeny decreased in favor of apomictically derived plants. Within the progeny of plants pollinated byH. pilosella, the proportion of polyhaploid progeny decreased significantly in favor of apomictically derived plants and 2n + n hybrids. It is argued that at least a proportion of the sexually derived progeny of this facultatively apomictic maternal parent has a lower survival rate than apomictically derived progeny.