Effects of hybridization and polyploidy on the embryo sac development in the apomictic Ranunculus auricomus complex

HOJSGAARD DH; HÖRANDL E

Bristol

Congreso; The 21st International Congress on Sex Plant Reproduction; 2010

Apomixis is an uncommon reproductive way of some polyploids of few angiosperms species. The origin of apomixis in natural population is still not well understood, but often connected to hybridization. Ranunculus auricomus is a polyploid complex which includes different natives species from Europe and Asia. Most of the species in the complex are tetraploid, aposporous and pseudogamous, with evidence of hybrid origin of apomictic taxa. Just four sexual species are known: R. carpaticola (with diploid sexual populations), R. cassubicifolius (with diploid and autotetraploid), R. marsicus (with sexual and apomictic tetraploids) and R. notabilis (diploid populations). In order to explore the effects of hybridization and ploidy levels on apomictic development we made experimental crosses between the distantly related diploid species R. notabilis X R. carpaticola and diploid R. notabilis X tetraploid R. cassubicifolius. The megagametogenesis and megasporogenesis were analysed on experimentally produced hybrids as well as in natural hybrids, in natural allopolyploid apomictics and their sexual progenitors. The reproductive development in diploid R. notabilis X R. carpaticola and triploid R. notabilis X R. cassubicifolius are compared with the sexual parents and natural apomictic polyploid species. The effects of interspecific hybridization and polyploidy on embryo sacs development, as a first step necessary for the shift from sexuality to apomixis, are discussed. The observed developmental staging is further the basis for comparative transcriptomics.