ABUNDANCE AND DISTRIBUTION OF SIMPLE SEQUENCE REPEATS IN THE MUSACEAE FAMILY: MICROSATELLITE MARKERS TO MAP THE BANANA GENOME

摘要

The usefulness of microsatellite derived markers is emphasized by implementing relatively simple laboratory techniques (polymerase chain reaction (PCR) and non-radioactive detection) compared with restriction fragment length polymorphism (RFLP) markers. Development of microsatellite markers is currently limited in plants because of the lack of available published sequence data for most species. This applies particularly to tropical crops such as the banana, but an increasing number of research groups are working on molecular characterization of these crops and there is no doubt that more DNA sequences will be available in the near future. A partial, size fractioned PstI genomic library for Musa, previously established as a source for RFLP makers, has been rescreened for dinucleotide repeats. Preliminary results are given of the dinucleotide microsatellite sequences in the banana genome. Roughly one-sixth (17%) of the clones of the banana library contain at least one microsatellite site, as confirmed by sequencing. Surprisingly, the majority of dinucleotide repeats found are of the (GA)_n sequence family. These recently developed microsatellite markers on the banana proved to be abundant and polymorphic (the number of alleles per locus varying between 11 and 24 in a testing panel of 19 accessions representing the different sections of the Musaceae family). Laboratory protocols have been streamlined and a previ-ously described high resolution, non-radioactive analysis procedure (based on denaturing silver stained polyacrylamide gel electrophoresis) has been adapted to detect the variable number of tandem repeat alleles in order to promote exportation of microsatellite markers (i.e. PCR assay kits containing extensively tested, robust, primer pairs) to developing countries. Preliminary results show the efficiency of polymorphic microsatellite markers for mapping and clonal identification using rapid and simple methods. All the microsatellites that have been detected in the banana to date are conserved in sections of the Musaceae family.