Studio dell'interazione cucumis melo – fusarium oxysporum f. sp. melonis: un approccio per caratterizzare le basi genetiche del dialogo tra ospite e patogeno

Fusarium oxysporum f. sp. melonis (FOM) is the causal agent of a sever vascular wilt disease of muskmelon (Cucumis melo) worldwide. In order to understand the molecular basis of resistance and susceptibility in melon and of virulence in the pathogen, a transcriptomic approach has been undertaken by AFLP-TP technique on stems of melon plants cv. Charentais-Fom2 infected with one isolate of race 1 (avirulent) and two isolates of race 1,2 (virulent), at 2, 4, 8 and 21 days after inoculation. RNA from fungal colonies of the three isolates has been also included in the analysis, to identify fragments specific of a single FOM race. The results of the analysis, performed running 128 primer combinations (F. Fusari and K. Szafranska), show that the majority of genes is modulated in the late stages of infection in the compatible interaction, due also to FOM gene expression in heavily infected plants; on the contrary few genes are expressed specifically in the incompatible interaction. 150 transcripts from the three FOM isolates grown in vitro are expressed only or mainly in a single FOM race. Totally 618 nucleotidic sequences (286 from melon and 332 from FOM) show at least one significant homology (E < 10-5) after comparison in databases (A. Ferrarini and F. Fusari). In view of the application of RNA interfering technique and the induction of silencing on genes putatively associated to FOM resistance (based on AFLP-TP results), the transformation system through Agrobacterium tumefaciens has been tested both in resistant (Nad-1) and susceptible (Charentais T) genotypes of melon. The results obtained demonstrate that the transformation system is valid on genotype Charentais T but not on Nad-1, which does not regenerate shoots from calluses. Another aim of this work is defining a model of disease development in melon through FOM inoculations (IsPaVe Roma) on grafted plants (susceptible scion on resistant rootstock and resistant scion on susceptible rootstock). The results suggest that the resistance mechanism is localized in the root system and there isn't a systemic signal towards stems.