A genetic linkage map of the diplosporous chromosomal region in Taraxacum officinale (common dandelion; Asteraceae)

Abstract

In this study, we mapped the diplosporous chromosomal region in Taraxacum officinale, by using amplified fragment length polymorphism technology (AFLP) in 73 plants from a segregating population. Taraxacum serves as a model system to investigate the genetics, ecology, and evolution of apomixis. The genus includes sexual diploid as well as apomictic polyploid, mostly triploid, plants. Apomictic Taraxacum is diplosporous, parthenogenetic, and has autonomous endosperm formation. Previous studies have indicated that these three apomixis elements are controlled by more than one locus in Taraxacum and that diplospory inherits as a dominant, monogenic trait ( Ddd; DIP). A bulked segregant analysis provided 34 AFLP markers that were linked to DIP and were, together with two microsatellite markers, used for mapping the trait. The map length was 18.6 cM and markers were found on both sides of DIP, corresponding to 5.9 and 12.7 cM, respectively. None of the markers completely co-segregated with DIP. Eight markers were selected for PCR-based marker development, of which two were successfully converted. In contrast to all other mapping studies of apomeiosis to date, our results showed no evidence for suppression of recombination around the DIP locus in Taraxacum. No obvious evidence for sequence divergence between the DIP and non- DIP homologous loci was found, and no hemizygosity at the DIP locus was detected. These results may indicate that apomixis is relatively recent in Taraxacum.

Insights into developmental processes in anthers, ovaries, and ovules of Taraxacum belorussicum (Asteraceae-Cichorioideae) using DIC optics

“…The effect of the environment on male sterility, especially the impact of day length and temperature, was reported in Cajanus cajan, where high temperatures and longer days maintained male-sterility, while shorter days and lower temperature induced male fertility (Saxena et al 2010). Similarly, in some individuals of the male-sterile diploid dandelions, the production of pollen depended on the temperature (Van der Hulst et al 2004). In the light of these findings, it can be assumed that the presence of pollen observed in the investigated individuals of male-sterile T. belorussicum from Poland is a sign of such intraspecific variation in pollen production, which may be affected by environmental factors.…”

“…Maynard Smith (1978) suggested that apomicts producing pollen are phylogenetically relatively young to have accumulated the necessary mutations that cause male sterility. However, male sterility has been found in both diploid sexual and apomictic dandelions representing numerous sections (Van Soest 1965;Richards 1970;Małecka 1971b; Van der Hulst et al 2004;Meirmans et al 2006). Pollen production is linked to a significant reproductive cost, thus, the male sterility in apomicts can be considered as a reallocation of resources from male function to increase female fitness.…”

“…Erythrosperma), Małecka (1971b) suggested for the first time the occurrence of cytoplasmic male sterility in dandelions. In further research, nuclear-cytoplasmic male sterility was found in sexually reproducing dandelions from two French populations ( Van der Hulst et al 2004). However, in male-sterile individuals of triploid dandelions from T. section Ruderalia, the results of crosses as well as microsatellites and the chloroplast haplotyping indicated that male sterility in apomictic dandelions has nuclear basis (Meirmans et al 2006).…”

“…Furthermore, crossing experiments and genetic analyses revealed that in Taraxacum these basic elements of apomictic developmental pathway are controlled by three dominant loci, and that diplospory, as well as parthenogenesis, are inherited independently, while the inheritance of autonomous endosperm formation is still not fully settled (Van Dijk et al 1999Van Dijk and BakxSchotmann 2004;Vijverberg et al 2004Vijverberg et al , 2010.…”

Sexual and asexual (apomictic) seed development in flowering plants: molecular, morphological and evolutionary relationships

“…If the hybridisation theory is correct, then the genomic regions controlling the initiation of apomixis might simply reflect key regulators of the sexual pathway that are mis-expressed in time and space. This may be an important point to consider as mapping and mutagenesis approaches in Pennisetum, Hieracium and Taraxacum and other apomictic species approach the core regions controlling apomixis in these plants (Vijverberg et al 2004;Akiyama et al 2005;Catanach et al 2006).…”