Mapping root and shoot traits in rice: experience in UK, IRRI and WARDA

A mapping population of 205 recombinant inbred lines derived from a cross between two drought-tolerant upland rice varieties, Azucena and Bala, has been used to identify genomic regions contributing to drought tolerance. We describe analyses of screens conducted in the dry season at the International Rice Research Institute (IRRI) over two seasons and at the West Africa Rice Development Association (WARDA) over one season. Performance under drought was assessed visually as leaf rolling and leaf drying and by measuring relative water content. Using a combined RFLP and AFLP map with 134 markers, quantitative trait loci (QTLs) with LOD >2.0 detected using composite interval mapping were found on all chromosomes except 4, 6, 8, and 11. The same population has been used to locate QTLs associated with root morphology assessed in two different greenhouse experiments in the UK. Maximum root length and root thickness traits were mapped and showed considerable plasticity. We discuss the results in the context of previous work on drought screening and root-morphology mapping with other populations and root penetration QTLs identified in this population. We also discuss progress toward identifying valuable regions for marker-assisted breeding. (Résumé d'auteur