Competition between meiotic and apomictic pathways during ovule and seed development results in clonality
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2013-01Autor
Hojsgaard, Diego Hernán
Martínez, Eric Javier
Quarin, Camilo Luis
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Meiotic and apomictic reproductive pathways develop simultaneously in facultative
aposporous species, and compete to form a seed as a final goal. This developmental competition
was evaluated in tetraploid genotypes of Paspalum malacophyllum in order to understand the
low level of sexuality in facultative apomictic populations.
Cyto-embryology on ovules, flow cytometry on seeds and progeny tests by DNA
fingerprinting were used to measure the relative incidence of each meiotic or apomictic
pathway along four different stages of the plant’s life cycle, namely the beginning and end of
gametogenesis, seed formation and adult offspring.
A high variation in the frequencies of sexual and apomictic pathways occurred at the first two
stages. A trend of radical decline in realized sexuality was then observed. Sexual and apomictic
seeds were produced, but the efficiency of the sexual pathway dropped drastically, and
exclusively clonal offspring remained.
Both reproductive pathways are unstable at the beginning of development, and only the
apomictic one remains functional. Key factors reducing sexuality are the faster growth and
parthenogenetic development in the aposporous pathway, and an (epi)genetically negative
background related to the extensive gene de-regulation pattern responsible for apomixis. The
effects of inbreeding depression during post-fertilization development may further decrease the
frequency of effective sexuality.
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