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Résumé :
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In order to characterize the mechanisms of resistance to M. persicae in several genotypes of peach and related species, the settling behaviour and bionomics of the aphid were investigated. In a no-choice test, all the nymphs put on Rubira and Weeping Flower Peach left the plants or died within 4 days. The susceptible peaches GF305 and Summergrand, but also the less favourable Male Konare and P. davidiana, were accepted as host-plant by aphids. The larval development time of aphids reared on Summergrand, Male Konare and P. davidiana was hardly affected compared to that of aphids reared on the highly susceptible GF305. By contrast, aphids feeding on GF305 had significantly more embryos in their gonads and laid more nymphs. The intrinsic rate of natural increase (rm), a synthetic index of biotic potential of aphid population, was the highest on GF305, intermediate on Summergrand and Male Konare and the lowest on P. davidiana. The analysis by Electrical Penetration Graph of aphid probing behaviour during penetration of stylets into the plant tissues showed that resistance was mainly linked to difficulties either to reach the phloem, or to initiate sap uptake or to sustain food ingestion. This study clearly demonstrates the existence of different mechanisms of resistance among the genotypes tested, and therefore their individual importance in a peach breeding programme for resistance to M. persicae.
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