IDENTIFICATION OF TOMATO GENES DIFFERENTIALLY EXPRESSED DURING COMPATIBLE INTERACTION WITH PYRENOCHAETA LYCOPERSICI

Breeding for resistance is the most effective tool for controlling the corky root disease of tomato caused by the fungus Pyrenochaeta lycopersici. However, little is known about the molecular bases of tomato-P. lycopersici interaction. In order to identify genes involved in the basal defence response activated in a susceptible cultivar and in disease symptom development, a set of cDNA-AFLP fragments derived from a profiling experiment was analysed. A total of 247 differentially expressed TDFs (transcript-derived fragments), identified as putative tomato genes, were characterized by similarity searches, and classified into 11 broad functional classes. Timings ranging between the early [48, 72 and 96 h post-infection (hpi)] and the late infection stages (20 and 27 dpi) were used. The changes of tomato root transcriptional profiles showed large differences in quantity and quality between the early and late stages of infection. Mechanisms of basal defence were most likely activated at early stages, when a gene coding for a receptor-like serine-threonine protein kinase and other genes of the signalling class were up regulated. At 20 dpi some of the mechanisms involved in defence were still activated, while at 27 dpi a general repression of gene expression was observed.