Meiotic recombination in sexual diploid and apomictic triploid dandelions (Taraxacum officinale L.)

TY - JOUR

T1 - Meiotic recombination in sexual diploid and apomictic triploid dandelions (Taraxacum officinale L.)

AU - Van Baarlen, P.

AU - Van Dijk, P.J.

AU - Hoekstra, R.F.

AU - De Jong, J.H.

N1 - Reporting year: 2000 Metis note: 2753; CTE; PVP; file:///L:/Endnotedatabases/NIOOPUB/pdfs/Pdfs2000/VanBaarlen_ea_2753.pdf

PY - 2000

Y1 - 2000

N2 - Taraxacum officinale L. (dandelion) is a vigorous weed in Europe with diploid sexual populations in the southern regions and partially overlapping populations of diploid sexuals and triploid or tetraploid apomicts in the central and northern regions. Previous studies have demonstrated unexpectedly high levels of genetic variation in the apomictic populations, suggesting the occurrence of genetic segregation in the apomicts and (or) hybridization between sexual and apomictic individuals. In this study we analysed meiosis in both sexual diploid and apomictic triploid plants to find mechanisms that could account for the high levels of genetic variation in the apomicts. Microscopic study of microsporocytes in the triploid apomicts revealed that the levels of chromosome pairing and chiasma formation at meiotic prophase I were lower than in that of the sexual diploids, but still sufficient to assume recombination between the homologues. Nomarski DIC (differential interference contrast) microscopy of optically cleared megasporocytes in the apomicts demonstrated incidental formation of tetrads, which suggests that hybridization can occur in triploid apomicts. [KEYWORDS: apomixis; autosegregation; diplospory; meiotic recombination; meiotic restitution; subsexual reproduction Genotypic variation; plants]

AB - Taraxacum officinale L. (dandelion) is a vigorous weed in Europe with diploid sexual populations in the southern regions and partially overlapping populations of diploid sexuals and triploid or tetraploid apomicts in the central and northern regions. Previous studies have demonstrated unexpectedly high levels of genetic variation in the apomictic populations, suggesting the occurrence of genetic segregation in the apomicts and (or) hybridization between sexual and apomictic individuals. In this study we analysed meiosis in both sexual diploid and apomictic triploid plants to find mechanisms that could account for the high levels of genetic variation in the apomicts. Microscopic study of microsporocytes in the triploid apomicts revealed that the levels of chromosome pairing and chiasma formation at meiotic prophase I were lower than in that of the sexual diploids, but still sufficient to assume recombination between the homologues. Nomarski DIC (differential interference contrast) microscopy of optically cleared megasporocytes in the apomicts demonstrated incidental formation of tetrads, which suggests that hybridization can occur in triploid apomicts. [KEYWORDS: apomixis; autosegregation; diplospory; meiotic recombination; meiotic restitution; subsexual reproduction Genotypic variation; plants]

KW - NIOO/CTE/PVP

U2 - 10.1139/gen-43-5-827

DO - 10.1139/gen-43-5-827

M3 - Article

SN - 0831-2796

VL - 43

SP - 827

EP - 835

JO - Genome

JF - Genome

IS - 5

ER -