title: Resistance to powdery mildew (Oidium lycopersicum) in Lycopersicon hirsutum is controlled by an incompletely-dominant gene Ol-1 on chromosome 6.
abstract: The inheritance of resistance to powdery mildew (Oidium lycopersicum) in Lycopersicon hirsutum was investigated by disease tests in segregating populations obtained by hybridising tomato (L. esculentum) cv Moneymaker with the wild relative L. hirsutum G1.1560. One incompletely dominant gene Ol-1 was found to largely control resistance to the disease. To map Ol-1, DNA pools from seven resistant and ten susceptible F2 plants were analyzed for random amplified polymorphic DNA (RAPD). With 32 primers tested, one RAPD, primed with the sequence 5'-GACGTGGTGA-3', was observed between the susceptible and the resistant bulks, which cosegregated with resistance in the F2 population of L. esculentum × L. hirsutum G1.1560. This RAPD was mapped on chromosome 6 by using an F2 (L. esculentum × L. pennellii) already mapped for 49 RFLPs. RFLP analysis of the F2 from L. esculentum cv Moneymaker × L. hirsutum G1.1560 demonstrated that Ol-1 maps near the Aps-1 region on chromosome 6, in the vicinity of the resistance genes to Meloidogyne spp. (Mi) and to Cladosporium fulvum (Cf-2/Cf-5).
authors.affiliation: Department of Vegetable and Fruit Crops, Centre for Plant Breeding and Reproduction Research (CPRO-DLO), P.O. Box 16, NL-6700 AA, Wageningen, The Netherlands.
authors.forename: J G
authors.initials: JG
authors.lastname: van der Beek
authors.forename: G
authors.initials: G
authors.lastname: Pet
authors.forename: P
authors.initials: P
authors.lastname: Lindhout