The Application of Ooubled Haploid Plants to Population ... - MSpace

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opposite strands of template DNA and if they are within amplifiable distance hm
each
other the DNA sequence between them is amplifid. RAPD polymorphisms are usually
based on base mutations within the amplifid sequence. RAPD markers are dominant
and therefore polymorphisrns are detected by the presence or absence of a DNA
product as a band.
STSs are unique sequences amplified by PCR using primers designed
according to specific sequences of DNA (Olson et al.. 1989). STSs focus on fow copy
number sequences and avoid highly repeüüve DNA sequences that may be identified
using the random primers with RAPD markers. The specific primers are usually longer
than the random prïmers used with RAPD analysis and therefore have a tendency to be
more stable under different PCR reaction conditions. STSs have also been shown to
be more efficient than RFLP markers in genome analysis of wheat (Talbert et al., 1994).
RAPD and RFLP marken cm be wnverted into STSs. The disadvantage of STSs not
present with RAPD markers is the requirement of sequence information for primer
development.
Microsatellites or SSRs are tandem repeats of two to five nucleotide DNA
sequences existing throughout eu karyotic genomes. Conserved DNA sequences
flanking the SSR can be used as primers or to create primers for PCR amplification of
the SSR. Polymorphic PCR products represent variation in the nurnber of tandem
repeats present in the genome. SSRs are abundant in plant genomes and high
polyrnorphism can be detected wmpared to RFLP (Morgante and Olivieri, 1993; Zhang
et al., 1995) and RAPD markers (Gupta et al., 1994). SSRs are codominant markers