Plant Genome III Conference Plant Genome III Conference
Simple sequence repeat (SSR) loci have been developed as genetic markers in sorghum The goal of this work is to create a small set of highly polymorphic PCR-based markers that can be used to rapidly and efficiently genotype sorghum germplasm both for the purposes of genetic resource conservation and for plant breeding. Three different strategies were used to identify sequences which flank polymorphic SSR loci and were suitable for use as primers. Fix-St, primers which were designed by other researchers to amplify SSR sequences in the Poaceae species Zea maize and Paspalum vaginatum were tested by PCR amplification of sorghum DNA. Second, all previously documented sorghum DNA sequences (GenBank release 83.0, EMBL release 38.0) were screened for the presence of SSRS. Third, plasmid and lambda libraries, of sorghum size-fractionated genomic DNA were constructed using the parental line RTx430. Selected dinucleotide repeat of oligonucleotides were used as probes to screen clones for the presence of SSR loci. Clones which hybridized to these probes were sequenced. Primers were designed to flank all identified sorghum SSR loci with greater than 12 repeating units. All three strategies have yielded SSR loci which are polymorphic among a small array of sorghum cultivars. We discuss the relative merits of each of these strategies for investigators interested in developing SSR markers for other plant species.