Plant, Animal & Microbe Genomes X Conference Plant, Animal & Microbe Genomes X ConferenceJanuary 12-16, 2002
Town & Country Convention Center
San Diego, CA
Workshop: Apomixis
Genetic mapping for triploid Erigeron (Asteraceae) indicates that two separate loci are required for the expression of full-blown apomixis. One of these loci is linked to diplosporous megagametophyte formation, while the other locus is associated with parthenogenetic seed production. The segregation of these two loci in F1 populations results in the occurrence of, for instance, diplosporous plants that produce zero apomictic seed. Co-occurrence of the two loci in F1s, furthermore, is consistently associated with apomictic seed production. The precise function of the parthenogenesis-linked locus (PLL) is uncertain, however. This is because it is unknown if the locus is linked to parthenogenesis, per se, or, rather, to some other developmental feature required for apomictic seed production, such as autonomous endosperm formation. Ongoing experiments aim to explore this enigmatic second apomixis locus. For example, crosses between triploid diplosporous maternal plants (completely lacking in apomictic seed production capacity) and sexual diploid individuals indicate that the former produce fully functional ovules that may combine additively to produce tetraploid progeny. This is consistent with the hypothesis that the PLL is likely associated with parthenogenesis. Furthermore, F1s of diplosporous maternal plants crossed with pollen donors possessing the PLL indicate that full-blown apomixis may be regenerated through recombination, but at lower than expected frequencies.