Identification of PCR-based markers (RAPD, AFLP) linked to a novel powdery mildew resistance gene ( ol-2) in tomato

Abstract

Tomato powdery mildew ( Oidium lycopersicum) is a recently reported plant disease which has a world-wide spread. The establishment of resistant cultivars appears to be a sustainable way to control the disease and to decrease the requirement for artificial anti-fungal treatments. In this paper, we present the results of a research aimed at the identification of PCR-based markers Random Amplified Polymorphic DNA, (RAPD) and Amplified Fragment Length Polymorphism, (AFLP) linked to the ol-2 gene that confers resistance to powdery mildew. To this purpose, bulked segregant analysis was applied to an F 2 population segregating for the ol-2 gene and derived from the pair-cross between a powdery mildew resistant line of Lycopersicon esculentum var. cerasiforme and the susceptible cultivar Super Marmande. A single RAPD marker, 1500 bp in size and designated as OPU3 1500, was detected in the susceptible bulk. The OPU3 1500 was converted to a CAPS marker and the estimation of the distance between the markers and the ol-2 gene was performed by linkage analysis in the F 2 population. An associated AFLP marker was identified by the evaluation of 26 primer combinations on the parents and bulk samples. Both the reliable localisation of the CAPS marker on the tomato map and the availability of two AFLPs could be used effectively for marker-assisted selection (MAS) of ol-2 in breeding programmes.