APPLICATION OF DISCRIMINANT-ANALYSIS TO ELECTRICAL PENETRATION GRAPHSOF THE APHID SITOBION-AVENAE FEEDING ON RESISTANT AND SUSCEPTIBLE WHEAT

The stylet penetration activities of Sitobion avenae F. were followed with an electronic method (DC-EPG) on resistant and susceptible wheat genotypes. Discriminant analysis was therefore applied to data evaluat ed on each electrical penetration graphs obtained (EPGs). The variable s which mostly explained the resistance-susceptibility status of the w heat genotypes appeared to be related to the ingestion sap event (as r epresented by pattern E2), either to the time preceding first occurren ce of a sap ingestion event or to the total time spent by the aphid in gesting sap from the sieve elements of the phloem. On the basis of the ir stylet penetration activities, individuals were separated into thre e blocks. The first one was made up the individuals tested on suscepti ble or slightly resistant wheat ('susceptible block'). The second one contained the individuals tested on two resistant genotypes ('resistan t block 1') and the third one regrouped the individuals tested on anot her resistant genotype ('resistant block 2'). These results are discus sed in relation to the possible mechanisms of wheat resistance to S. a venae.