Plant Genome IV Conference Plant Genome IV Conference
Comparative RFLP maps of the major cereals are now well advanced. We are applying these to align the probable locations of major genes and QTL for important agronomic traits. In the Triticeae comparative analysis has allowed us to align loci controlling a range of traits, such as flowering time, stress responses and plant height across the genomes of wheat, barley and rye. These analyses are also exploiting the comparative advantages of the different species to search and accurately locate loci. Thus the diploid genetics and facile doubled haploid systems in barley can be exploited for whole genome searches for QTL, whilst aneuploid and chromosome substitution line approaches in wheat can accurately locate detected QTL by segregational analysis. The latter reduces QTL variation to major gene variation and thus allows the possiblities of fine mapping and chromosome walking to target loci. Using these approaches, for example, homoeologous variation for major genes and QTL involved in flowering time has been detected and mapped so that separate loci controlling vernalization response, photoperiod and "earliness per se" have been assigned. The loci detected probably account for the majority of the genetical variation controlling adaptation of these temperate cereals to most environments where they are grown. We are now extending these analyses to rice and maize to correlate the extent of homoeologous variation for QTL across the wider taxonomic distance.