Corynespora cassiicola, causing agent of the Corynespora Leaf Fall (CLF) of rubber tree, is an Ascomycete fungus able to infect a large range of plants, mostly in tropical areas or green houses. Over the past 20 years, the CLF disease has gained increasing impo1tance in all Asian and African rubber producing countries but has not been declared so far in South America. lt causes massive sporadic leaf falls, thus impacting the yield of rubber production. Susceptibility of the various rubber clones to the disease varies depending on the geographical location, suggesting an important diversity of the natural inoculum. The biology of the fungus is complex since it has been described as a necrotrophic pathogen as well as an endophyte or a saphophyte. In this presentation, I will give a broad description of the research program that we are developing for the characterization of fungal effectors involved in the H. brasiliensis/C. cassiicola interaction. Our objective is to describe the diversity of the C. cassiicola species, trying to connect the genetic races with specific effectors potentially involved in virulence or host specialization of the isolates. In this program, we have first used biochemical and molecular approaches, which lead to the characterization of the cassiicolin toxin, a small secreted protein (SSP) putatively involved in the pathogenicity of C. cassiicola (isolate CCP) (Barthe et al., 2007; Breton, Sanier, & d'Auzac, 2000; de Lamotte et al., 2007; Deon et al., 2012a). A phylogenetic analysis based on C. cassiicola isolates of various geographical origins and host plants identified at least 8 phylogenetic clades (Deon et al., 2014). In addition, a classification based on the cassiicolin gene diversity was proposed (toxin classes). We found a rather good coherence between the toxin classes and the phylogenetic clades. However, 53% of the isolates did not carry any casssicolin gene, although some of them are virulent, suggesting the existence of effectors