Molecular strategies for the study of tomato-Pyrenochaeta lycopersici interaction

Tomato Corky Root (CRR) is a soil-borne disease, caused by the hemibiotrophic fungus Pyrenochaeta lycopersici that has recently become a disease of concern for many tomato-growing areas including major producers such as China, USA, Italy and Japan, both in greenhouses and in field. The molecular bases of interaction between tomato and P. lycopersici are still poorly understood and breeding for resistance remains the most effective tool for controlling the disease. We are currently investigating the mechanisms behind disease susceptibility and resistance against CRR using different molecular methods. A cDNA-AFLP based approach was employed for transcriptomic analysis of the fungus-plant interaction and led to the identification of fungal genes putatively involved in plant pathogenesis and in the disease symptoms development (Aragona and Infantino, 2008). Among several differentially transcribed fragments we focused on a P. lycopersici sequence having a high similarity with a β-glucanase gene. We cloned the full genomic sequence of the endo-1,4 β-glucanase gene isolated and analyzed its expression in susceptible and resistant tomato cultivars, with the final goal of identifying its role in the interaction with tomato. For expression analysis, a real-time PCR-based approach was conducted on tomato roots artificially infected with P. lycopersici at six different post-infection time points, compared to vegetative mycelium. The quantification of P. lycopersici biomass in relation with plant biomass was assessed and a correlation between expression of the glucanase gene and the progress of P. lycopersici during the time course of root infection was elucidated.