Progress in apomixis research

Abstract

Apomixis in the angiosperms comprises different kinds of asexual reproduction, wholly or partly replacing the sexual cycle. Recent views on evolutionary advantages and drawbacks of apomixis are surveyed. Gametophytic apomixis implies two main deviations from sexual reproduction: the formation of unreduced embryo‐sacs, and the capacity of their egg cells for parthenogenetic development. Examples are discussed where either of these phenomena occur in sexual taxa. – The genetics of apospory has been elucidated in some cases. In Ranunculus auricomus and Panicum maximum, apospory is controlled by one pair of alleles, and is not recessive to sexuality. The mode of reproduction is influenced by the pollinator (cf. induced parthenogenesis in sexuals) and environmental factors, as well as by level of ploidy. Diploid‐tetraploid‐haploid (‐diploid) cycles with alternations between apomixis and sexuality are known in grasses and in Potentilla. Crossing experiments between sexual crops and related apomicts have been performed, for instance between maize and Tripsacum dactyloides, and between sugar beet and Beta lomatogona. Attempts are made to select apomicts (partly following mutagen treatment) after cloning of vigorous but sterile hybrids between Festuca and Lolium species. To manipulate apomixis in breeding, research in its basic mechanisms and gene background should be intensified. © 1979 Mendelian Society of Lund