Nadia Talent: Publication abstract
Talent, Nadia and Timothy A. Dickinson 2007. Apomixis and hybridization in Rosaceae subtribe Pyrineae Dumort.: a new tool promises new insights. In Apomixis: Evolution, Mechanisms and Perspectives, edited by E. Hörandl, U. Grossniklaus, P. J. Van Dijk, and T. Sharbel. Regnum Vegetabile 147, International Association for Plant Taxonomy and Koeltz Scientific Books, Vienna, pp. 301-316.
The knowledge base about certain genera of the pome-bearing clade of Rosaceae (subfamily Spiraeoideae (Juss.) Arn., tribe Pyreae Baill., subtribe Pyrinae Dumort., traditionally referred to as subfamily Maloideae C. Weber), e.g., Malus Mill. and Pyrus L., is considerable because of their great economic importance. However, what is known relates primarily to the domesticated species and much less is known about the much more numerous wild species. Several small genera appear to be sexual diploids, and the larger genera that have been studied (Amelanchier Medik., Cotoneaster Medik., Crataegus L., Malus Mill., and Sorbus L. s.l.) are taxonomically complex because they include apomictic polyploids as well as sexual diploids. Multiple taxonomic sections of the largest genera also include both apomictic polyploids and sexual diploids. In Crataegus, we hope to shed light on how often apomixis has arisen, and on the nexus between polyploidy, hybridization, and apomixis. Flow cytometric DNA measurement boosts the efficiency of ploidy-level determination, allowing us to survey cytological variation in wild populations. Flow cytometry also reveals the ploidy levels of embryos and endosperm in mature seeds, and these indicate whether the embryo sac was meiotically unreduced. Whereas embryological observations of apomixis can be difficult to interpret, the cytometric data give a simpler picture and are more indicative of the final reproductive outcome. Our results indicate that, in Crataegus, one of the two meiotically reduced sperm from diploids or tetraploids is frequently available to fertilize the unreduced egg cells of apomictic triploids and tetraploids, yielding higher-ploid offspring. This improved ability to survey ploidy level and breeding system will help us to interpret the results of molecular and genetic studies.
Keywords: Crataegus, endosperm balance, flow cytometry, Maloideae, Rosaceae, polyploidy, pseudogamous apospory, Pyreae, Spiraeoideae.
Last modified 17 July 2008