TY - JOUR
T1 - The role of tetraploids in the sexual-asexual cycle in dandelions (Taraxacum)
AU - Verduijn, M.H.
AU - van Dijk, P.J.
AU - Van Damme, J.M.M.
N1 - Reporting year: 2004
Metis note: 3312; CTE; PVP; file:///L:/Endnotedatabases/NIOOPUB/pdfs/Pdfs2004/Verduijn_ea_3312.pdf
PY - 2004
Y1 - 2004
N2 - Apomictic plants often produce pollen that can function in crosses with related sexuals. Moreover, facultative apomicts can produce some sexual offspring. In dandelions, Taraxacum, a sexual-asexual cycle between diploid sexuals and triploid apomicts, has been described, based on experimental crosses and population genetic studies. Little is known about the actual hybridization processes in nature. We therefore studied the sexual-asexual cycle in a mixed dandelion population in the Netherlands. In this population, the frequencies of sexual diploids and triploids were 0.31 and 0.68, respectively. In addition, less than 1% tetraploids were detected. Diploids were strict sexuals, triploids were obligate apomicts, but tetraploids were most often only partly apomictic, lacking certain elements of apomixis. Tetraploid seed fertility in the field was significantly lower than that of apomictic triploids. Field-pollinated sexual diploids produced on average less than 2% polyploid offspring, implying that the effect of hybridization in the 2x-3x cycle in Taraxacum will be low. Until now, 2x-3x crosses were assumed to be the main pathway of new formation of triploid apomicts in the sexual-asexual cycle in Taraxacum. However, tetraploid pollen donors produced 28 times more triploid offspring in experimental crosses with diploid sexuals than triploid pollen donors. Rare tetraploids may therefore act as an important bridge in the formation of new triploid apomicts. [KEYWORDS: Taraxacum; apomixis; sexual-asexual cycle; hybridization; polyploidy]
AB - Apomictic plants often produce pollen that can function in crosses with related sexuals. Moreover, facultative apomicts can produce some sexual offspring. In dandelions, Taraxacum, a sexual-asexual cycle between diploid sexuals and triploid apomicts, has been described, based on experimental crosses and population genetic studies. Little is known about the actual hybridization processes in nature. We therefore studied the sexual-asexual cycle in a mixed dandelion population in the Netherlands. In this population, the frequencies of sexual diploids and triploids were 0.31 and 0.68, respectively. In addition, less than 1% tetraploids were detected. Diploids were strict sexuals, triploids were obligate apomicts, but tetraploids were most often only partly apomictic, lacking certain elements of apomixis. Tetraploid seed fertility in the field was significantly lower than that of apomictic triploids. Field-pollinated sexual diploids produced on average less than 2% polyploid offspring, implying that the effect of hybridization in the 2x-3x cycle in Taraxacum will be low. Until now, 2x-3x crosses were assumed to be the main pathway of new formation of triploid apomicts in the sexual-asexual cycle in Taraxacum. However, tetraploid pollen donors produced 28 times more triploid offspring in experimental crosses with diploid sexuals than triploid pollen donors. Rare tetraploids may therefore act as an important bridge in the formation of new triploid apomicts. [KEYWORDS: Taraxacum; apomixis; sexual-asexual cycle; hybridization; polyploidy]
KW - NIOO/CTE/PVP
U2 - 10.1038/sj.hdy.6800515
DO - 10.1038/sj.hdy.6800515
M3 - Article
SN - 0018-067X
VL - 93
SP - 390
EP - 398
JO - Heredity
JF - Heredity
IS - 4
ER -