Abstract
Microsatellite cross-species amplification in the genus Centaurea (Compositae).- Microsatellites are widely used for population genetic studies although the development of these species-specific markers is costly and time-consuming. One strategy for saving time and money is the use of markers developed for one species (source species) in a different species (target species). This is known as cross-amplification. In the present work, two sets of microsatellites are used to test their transferability to six narrow endemic Centaurea species: i) 16 nuclear loci previously published for three congeneric species and ii) 10 universal chloroplast markers designed from Nicotiana tabacum sequences. Seventeen of the 26 markers tested were transferable and 14 of them were also polymorphic and therefore useful for future works. Nuclear markers were more variable and thus more informative than chloroplast markers. Interspecific amplification performed better for the nuclear loci developed for different Centaurea species than for the universal chloroplast markers developed for Nicotiana tabacum. Likewise, transferability was more successful for the species from sect. Phalolepis than for sect. Lepteranthus. Therefore, our results support the idea that the success of the cross-amplification is influenced by the evolutionary distance between the target and the source species.
Highlights
Single Sequence Repeats (SSR), known as microsatellites, are widely used to investigate genetic variability and structure both at population and species level
The overall percentage of polymorphic loci for the transferable nuclear markers was 92.5% ranging from 100% for C. chrysocephala, C. emigrantis, C. litochorea and C. princeps to 75% for C. heldreichii (Table 5)
The amplification process was slightly less successful for the set of universal chloroplast markers developed for Nicotiana tabacum, than for the set of nuclear markers developed for different Centaurea species (60% and 68.75% of the loci amplified respectively)
Summary
Single Sequence Repeats (SSR), known as microsatellites, are widely used to investigate genetic variability and structure both at population and species level These genetic markers are tandemly repeated units from one to six nucleotide in length distributed evenly throughout the genome and present in almost every organism so far studied (Hancock, 1999). Regarding chloroplast microsatellites, Ebert & Peakall (2009) state that “when genus-specific cpSSR primers are available, cross-species amplification can often be fruitful”. They point out that “while potentially useful, universal cpSSR primers at best provide access to only a small number of variable markers”. According to Kantety et al (2002) the frequency of SSR-containing sequences in plant-derived EST databases is only around 2% and 5%
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