ADVANCES IN BREEDING MELONS FOR RESISTANCE TO VINE DECLINE

The melon vine decline syndrome is a major problem for melon production in many areas of the world. Our laboratory has been working for several years with the resistance derived from the accession Pat 81 of the subsp. agrestis of Cucumis melo. This accession tolerates vine decline by two mechanisms: a specific resistance to the pathogenic fungi and the development of a longer and more branched root system that allows it to escape infection by exploring a larger volume of soil. In our breeding programs, we are conducting a combined selection for resistance to fungi and for favorable root structure. However, the complex etiology of the disease, the strong environmental influence and the lack of reliable methods for disease severity assessment and for root structure analysis, limit the advance of breeding programs. Currently, we are introducing new technologies that allow us to accelerate breeding programs. Real-time PCR makes possible a quantitative detection of Monosporascus cannonballus, the main causal organism of melon vine decline, in melon roots from the very first stages of infection. Additionally, many of the difficulties encountered during the analysis of root structure can be overcome by combining in vitro culture techniques with root image analysis, using specific computer software. This system even allows us to perform in vivo studies of root development. As a result of these breeding programs, we have obtained several breeding lines with acceptable agronomic value and resistance to melon vine decline.