The Development of the Female Gametophyte in Fragaria x Ananassa Duch. cv. Selva

Abstract

Megasporogenesis and female gametophyte development were investigated in ovules of the everbearing strawberry Fragaria × ananassa Duch. cv. Selva. Observations of thin sections revealed that ovule development starts from the formation of a nucellus and coincides in time with the beginning of receptacle overgrowth. The most characteristic feature during nucellus differentiation is the formation of a multicellular archesporium, beginning from at least two cells. Analysis of female gametophyte development indicated that in addition to the meiotic mode, female gametophytes develop by an apomeiotic mode of Antennaria type. Asynchronous development of female gametophytes of different origin occurs. The mature, eight-nucleate, seven-celled female gametophyte of meiotic origin is cylindrical and slightly curved. It occupies the central part of the nucellus. The egg apparatus, consisting of an egg cell and two synergids, is formed in the micropylar part of the female gametophyte; the opposite chalazal pole is occupied by antipodal cells. Besides the ovule in which only one seven-celled female gametophyte finally develops, ovules with a different number of cells were observed to initiate female gametophyte development. Some ovules contain a nucellus with a tetrad of linearly arranged megaspores surrounded by enlarged cells, each of which has the potential to develop into an apomictic female gametophyte. After degeneration of some post-meiotic cells or developmentally advanced female gametophytes, some of the chalazal cells initiated female gametophyte development.K Ke ey y w wo or rd ds s: : Fragaria × ananassa, megasporogenesis, multicellular archespore, female gametophyte, ovule, apomixis.

Asexual Female Gametogenesis Involves Contact with a Sexually-Fated Megaspore in Apomictic Hieracium

“…JIM13 and JIM15 antibodies detect epitopes present in cell walls of multicellular archesporial cells and cells designated as MMCs and female gametophytes in the facultatively apomictic strawberry (Fragaria spp. ; Dziadczyk et al, 2011;Leszczuk and Szczuka, 2018). Arabinogalactan proteins also are detected in maturing asexual female gametophytes of apomictic Taraxacum spp., which develop by mitotic diplospory (Gawecki et al, 2017).…”

Sex and Rosaceae apomicts

“…(Eriksen & Töpel, 2006;Feng & al., 2017). Gametophytic apomixis in Fragaria L. (also Potentilleae), however, appears to be evident only following hybridization (Asker & Jerling, 1992;Dziadczyk & al., 2011;Leszczuk & al., 2018), although even then evidence for its occurrence has been seen as equivocal (Nosrati & al., 2010;Dobeš & al., 2015). Confirmation of the hybrid status of several Fragaria species by Kamneva & al.…”