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Abstract

The pea aphid (Acyrthosiphon pisum HARRIS), a legume specialist, encompasses at least 11 genetically distinct sympatric host
races. Each host race shows a preference for a certain legume species. Six pea aphid clones from three host races were used
to localize plant factors influencing aphid probing and feeding behavior on four legume species. Aphid performance was
tested by measuring survival and growth. The location of plant factors influencing aphid probing and feeding was
determined using the electrical penetration graph (EPG) technique. Every aphid clone performed best on the plant species
from which it was originally collected, as well as on Vicia faba. On other plant species, clones showed intermediate or poor
performance. The most important plant factors influencing aphid probing and feeding behavior were localized in the
epidermis and sieve elements. Repetitive puncturing of sieve elements might be relevant for establishing phloem feeding,
since feeding periods appear nearly exclusively after these repetitive sieve element punctures. A combination of plant
factors influences the behavior of pea aphid host races on different legume species and likely contributes to the
maintenance of these races