Lycopersicon peruvianum LA2172 is completely resistant to Oidium neolycopersici, the causal agent of tomato powdery mildew. Despite the large genetic distance between the cultivated tomato and L. peruvianum, fertile F-1 hybrids of L. esculentum cv. Moneymaker x L. peruvianum LA2172 were produced, and a pseudo-F-2 population was generated by mating F-1 half-sibs. The disease tests on the pseudo-F-2 population and two BC1 families showed that the resistance in LA2172 is governed by one dominant gene, designated as Ol-4. In the pseudo-F-2 population, distorted segregation was observed, and multi-allelic, single-locus markers were used to display different marker-allele configurations per locus. Parameters for both distortion and linkage between genetic loci were determined by maximum likelihood estimation, and the necessity of using multi-allelic, single-locus markers was illustrated. Finally, a genetic linkage map of chromosome 6 around the Ol-4 locus was constructed by using the pseudo-F-2 population.
- bridge lines