Isolation of a diploid, apomictic plant of Hieracium aurantiacum

 As in most taxa that contain gametophytic apomicts, all of the apomictic biotypes studied so far in the genus Hieracium subgenus Pilosella have been recorded as polyploids. As part of a study of variation in apomictically derived populations of H. aurantiacum, a diploid plant was identified. Apospory, the mechanism of apomixis typically observed in this taxon, was observed in this plant. Unreduced megagametophytes at various developmental stages were commonly observed in the developing ovules, and endosperm formation was autonomous. The eventual seed set, however, was low. This appears to have been due to the proliferation of competing megagametophytes and embryos within each ovule. Pollen sterility was also observed, primarily resulting from the dysfunction of microgametogenesis at the uninucleate stage. Received: 3 September 1996 / Revision accepted: 21 March 1997