Corynespora cassiicola is a necrotrophic fungus infecting a wide range of more than 70 host plants, including rubber tree (Hevea brasiliensis). During the past decade, the pathogen has caused extensive damage to rubber tree cultivation in all the producing areas. It affects both mature and immature leaves, causing typical necrotic lesions along the veins and leading to massive defoliation. Culture filtrate from C. cassiicola isolates contain a toxin, named cassiicolin, able to induce leaf disease symptoms identical to those observed after fungal inoculation. An optimized protocol for the purification of this toxin has been set up. It includes mainly one step of reverse phase separation followed by gel filtration, each step being monitored by a biotest on Hevea leaves. The toxins produced by two C. cassiicola isolates of different aggressiveness and geographical origin (CCP and BCA3) were purified and analysed by mass spectrometry, revealing that both toxins were identical in mass. The primary sequence of the CCP toxin was determined by Edman sequencing. RMN analysis is under way for both CCP and BCA3 toxins to determine their 3D structure and confirm whether or not they are identical. (Texte intégral)