Genome-wide dissection of Fusarium resistance in tomato reveals multiple complex loci

Resistance to different pathogenic races of Fusarium oxysporum f. sp. lycop ersici (F. o. lycopersici) was explored at two genomic levels in tomato. Si x independent Fusarium resistance loci were identified by comparing the res ponses of a complete set of 53 lines carrying different introgressed region s of the Lycopersicon pennellii genome in a L. esculentum background. The l oci confer varying degrees of resistance to different races of the pathogen . Corresponding map positions from different tomato species were aligned an d in some cases. revealed parallel resistance to F. o. lycopersici with qua litative changes in race specificities. One of the loci identified correspo nds to the previously characterized complex resistance locus 12, which is i nvolved in resistance to F. o. lycopersici race 2. A novel member of this l ocus, I2C-5, which belongs to the NBS-LRR family of resistance genes, was c loned and shown to confer partial resistance in transgenic plants. Thus, at a particular complex locus gene members can confer fall or partial resista nce to F. o. lycopersici race 2. The results of our whole-genome mapping an alysis underline the robust independent origin of resistance to a particula r disease and demonstrate the conservation of resistance features at synten ic loci, together with the rapid diversification of genes for innate resist ance within loci.