This mission was conducted in the frame of the SMOU 2 passed between the Rubber programme of Cirad-cp (France) and RRIT-DOA (Thailand) and devoted to the "application of molecular biology in relation to plant breeding and plant physiology of the rubber tree". The mission was aiming at giving training in some biochemistry techniques and at continuing a collaborative research project on oxidative stress in the laticiferous tissus. Analysis of thiols, ascorbic acid, proteins and dehydroascorbate reductase activity were performed on clones RRIM600, GT1 and PB235 at different stimulation frequencies