Probing behaviour of Myzus persicae on tomato plants containing Mi gene or BTH-treated evaluated by electrical penetration graph

The probing behaviour of the green peach aphid, Myzus persicae Sulzer (Rhynchota Aphididae) was evaluated by electrical penetration graph (EPG-DC) on the tomato (Solanum lycopersicum L. syn. Lycopersicon esculentum Mill.) cultivar Motelle, containing the Mi gene conferring resistance to the potato aphid, Macrosiphum euphorbiae (Thomas) (Rhynchota Aphididae), to test the resistance degree of the cultivar to M. persicae. The aphid probing behaviour was also evaluated on a susceptible (mi) tomato cultivar, Moneymaker, after treatment by a chemical plant resistance elicitor, benzo(1,2,3)thiadiazole-7-carbothioic acid S-methyl ester (benzothiadiazole or BTH). Concerning a possible antixenotic effect due to physical and chemical barriers, no significant differences were found between the two cultivars in the probing and phloem phases. However, a difference was detected between the preinfested and non-preinfested susceptible cultivar in the total duration of phloem ingestion. The lack of significant differences in the entire process of host feeding between resistant and susceptible cultivars is probably due to the fact that the resistant cultivar identifies only the specific elicitors produced by M. euphorbiae. By contrast, the BTH treatment apparently makes the susceptible cultivar less palatable to a generalist aphid like M. persicae: the main component of this induced resistance is the reduced phloem ingestion.