Abstract
Polyploidy is a widespread phenomenon among higher plants and a major factor shaping the structure and evolution of plant genomes. The important ornamental chrysanthemum (Chrysanthemum indicum hybrid) possesses a hexaploid genome with 54 chromosomes and was classified based on its evolutionary origin and cytological methods as an allopolyploid. However, it is questionable whether cytological methods are sufficient to determine the type of ploidy, and there are more informative methods available based on molecular marker analyses. Therefore, we collected segregation data for 406 dominant molecular marker alleles [327 amplified fragment length polymorphism (AFLPs), 65 single-strand conformation polymorphism (SSCPs) and 14 microsatellites (EST-SSRs)] in a biparental F1 population of 160 individuals. We analyzed these data for the characteristics that differ between allopolyploids and autopolyploids, including the segregation ratio of each marker, the ratio of single-dose (SD) to multi-dose (MD) markers, the ratio of SD markers in coupling to those in repulsion and the banding patterns of the SSRs. Whereas the analysis of the segregation ratio of each polymorphic marker indicated disomic (13 markers) as well as hexasomic (eight markers) inheritance, the ratio of SD markers in coupling to those in repulsion was 1:0, which is characteristic of autopolyploids. The observed ratio of SD to MD markers was 0.67:0.33 which is significantly different to the expected segregation for auto- and allohexaploids. Furthermore, the three EST-SSR alleles were inherited in all possible combinations and were not independent of each other, as expected for fixed heterozygosity in allopolyploids. Combining our results with published cytological data indicates that cultivated chrysanthemums should be classified as segmental allohexaploids.
Highlights
Chrysanthemums (Chrysanthemum indicum hybrid, C. x grandiflorum or C. morifolium) are among the most economically important ornamental plants worldwide and are produced as cut flowers and as potted or garden plants
Because cultivated chrysanthemums resulted from hybridization events between different species, and because the occurrence of bivalent chromosomes is detected in meiosis in all four investigated polyploid Chrysanthemum accessions (Watanabe, 1977; Li et al, 2011), the cultivated forms are currently classified as allohexaploids
We describe the use of amplified fragment length (AFLP), single-strand conformation polymorphism (SSCP) and microsatellite (SSR) markers in a segregating biparental F1 population to investigate the type of ploidy of cultivated chrysanthemums
Summary
Chrysanthemums (Chrysanthemum indicum hybrid, C. x grandiflorum or C. morifolium) are among the most economically important ornamental plants worldwide and are produced as cut flowers and as potted or garden plants. Cultivated chrysanthemums are generally believed to be the result of natural hybridization involving several different species, such as C. indicum L., C. morifolium, C. vestitum, and C. lavandulifolium (Vogelmann, 1969; Dai et al, 1998; Yang et al, 2006) These crosses led to the formation of a hexaploid hybrid complex with 54 chromosomes (Dowrick, 1953). Polyploid genomes can be highly dynamic, and Stebbins (1947) proposed that it might be difficult to unambiguously classify the type of ploidy of an organism This was indicated by Watanabe (1983) for the hexaploid C. japonense, which is not believed to be a progenitor of the C. indicum hybrid, reporting a very limited formation of multivalents (3.8%) using microscopic methods. It is necessary to combine cytological and molecular methods to clarify the type of ploidy
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
