Plant Genome III Conference Plant Genome III Conference
The value of plant genome projects and their application in practical breeding programs are well understood. Detailed genetic maps are available for most of the major cereal species. Marker technology is now slowly moving from hybridization-based RFLP markers to PCR-based markers, such as sequence tagged sites (STS) and microsatellites, as these are more easily and more economically handled in commercial applications. A perceived problem, at least in some cases, of species-specificity of PCR-primers may, however, limit the use of these markers to intraspecific applications. The ability of RFLP markers to detect sequences with a reasonable degree of homology across a range of species has been exploited to analyse genome relationships. A hitherto unperceived generality has been exposed i.e. that the arrangement of genes along the chromosomes of different cereal species is remarkably conserved. Initially, this finding was restricted to close relatives - within the Triticeae cereals, within the Oryzeae and within the Andropogoneae. The comparative maps of the Triticeae cereals - wheat, barley and rye - have already provided clear evidence of both colinearity and the nature of evolutionary translocations. The former has been exploited in locus prediction and the latter in the formulation of more effective strategies for interspecific introgression. Recently, this conservation has been shown to have been maintained over as long as 60 million years and to extend across the entire grass family. Work is underway to formally align the many genomes of the Poaceae species. It is likely that grass comparative genetics will adopt rice as the pivotal genome. The immediate benefits of the comparative approach are perceived to lie in increased availability of markers in any grass crop, the availability of a new precise tool for evolutionary studies, the possibility to isolate genes in any grass by map-based DNA walking in rice, and the potential to predict the locations and mechanism of key genes in all species from their previous analysis in another.