Linkage mapping in the oilseed crop Jatropha curcas L. reveals a locus controlling the biosynthesis of phorbol esters which cause seed toxicity.
Bottom Line: As an important step towards the development of genetically improved varieties of J. curcas, we constructed a linkage map from four F₂ mapping populations.The linkage map provides a framework for the dissection of agronomic traits in J. curcas, and the development of improved varieties by marker-assisted breeding.The identification of the locus responsible for PE biosynthesis means that it is now possible to rapidly breed new nontoxic varieties.
Affiliation: Centre for Novel Agricultural Products, Department of Biology, University of York, York, UK.Show MeSH
Mentions: To build a linkage map of J. curcas, we used four mapping populations created from parental lines displaying differences in a range of traits as shown in Table1. Genotyping assays were performed using both SNP and SSR markers according to the Experimental procedures section. The linkage maps for each mapping population were built individually using CRI-MAP 2.503 (www.animalgenome.org), which uses the multipoint likelihood to calculate genetic distances (Lander et al., 1987). Each map contained 11 linkage groups, which is consistent with cytological evidence showing J. curcas is diploid with 22 chromosomes (n = 11) (Dehgan and Webster, 1979). After completion and error checking of the individual maps, the genotype files were merged and then used to build an integrated linkage map (Figures1 and 2). The total genetic distance of this integrated map was 717.0 cM, with an average marker density of 1.5 and 1.8 cM for all and unique loci, respectively. There are relatively few gaps within the integrated map, with only two pairs of loci separated by more than 15 cM, seven pairs of loci by more than 10 cM, and 30 pairs of loci by more than 5 cM. A summary of the map size, number of markers, unique loci and average marker density for each of the individual maps is shown in Table2. The individual maps are presented in File S5. Although marker densities and numbers were lower for the individual maps, the average density and length were in each case still high compared to first generation maps for most species. The least populated map (G51 × CV) still contained 253 markers and had a mean density of 3.3 cM based on unique loci. The marker coverage on all four maps is sufficient for interval mapping, where an interval of 10 cM is regarded as adequate (Mayer, 2005).
Affiliation: Centre for Novel Agricultural Products, Department of Biology, University of York, York, UK.