SUMMARYThe egg parasitoid Trissolcus basalis (Wollaston) (Hymenoptera:Scelionidae) responded to synomones emitted by leguminous plants induced by feeding and oviposition activity of the bug Nezara viridula (L.)(Heteroptera: Pentatomidae). This was shown by laboratory bioassays using a Y-tube olfactometer. Broad bean leaves (Vicia faba L.) damaged by feeding activity of N. viridula and on which host egg mass had been laid produced synomones that attracted T. basalis. By contrast,undamaged leaves or feeding-damaged leaves without eggs did not attract wasp females. French bean plants (Phaseolus vulgaris L.) also emitted attractive synomones when they were damaged by host feeding and carrying egg masses. Thus, release of feeding- and oviposition-induced synomones does not seem to be plant-specific. Synomone production was shown to be a systemically induced plant physiological response to feeding damage and oviposition. Also,parts of the plant that were left undamaged and did not carry host eggs emitted attractive synomones when other parts of the plant were damaged by feeding and carrying eggs. Furthermore, wasps were not attracted by N. viridula egg masses offered alone or combined with damaged broad bean leaves. Thus, the attractiveness of feeding-damaged leaves carrying eggs is due to induction by feeding and oviposition rather than due to a combined effect of attractive volatiles released from eggs and damaged leaves. The production of synomones was influenced by the age of the host egg mass,because feeding-damaged leaves bearing egg masses attracted the parasitoid until the eggs were ∼72-96 h old but not once the larvae had hatched from the eggs (∼120 h old). These results show that annual plants are able to produce synomones as a consequence of feeding and egg mass oviposition by a sucking insect.

Polygalacturonase-inhibiting proteins (PGIPs) are extracellular plant inhibitors of fungal endopolygalacturonases (PGs) that\ud belong to the superfamily of Leu-rich repeat proteins. We have characterized the full complement of pgip genes in the bean\ud (Phaseolus vulgaris) genotype BAT93. This comprises four clustered members that span a 50-kb region and, based on their\ud similarity, form two pairs (Pvpgip1/Pvpgip2 and Pvpgip3/Pvpgip4). Characterization of the encoded products revealed both\ud partial redundancy and subfunctionalization against fungal-derived PGs. Notably, the pair PvPGIP3/PvPGIP4 also inhibited\ud PGs of two mirid bugs (Lygus rugulipennis and Adelphocoris lineolatus). Characterization of Pvpgip genes of Pinto bean showed\ud variations limited to single synonymous substitutions or small deletions. A three-amino acid deletion encompassing a residue\ud previously identified as crucial for recognition of PG of Fusarium moniliforme was responsible for the inability of BAT93\ud PvPGIP2 to inhibit this enzyme. Consistent with the large variations observed in the promoter sequences, reverse\ud transcription-PCR expression analysis revealed that the different family members differentially respond to elicitors, wounding,\ud and salicylic acid. We conclude that both biochemical and regulatory redundancy and subfunctionalization of pgip genes are\ud important for the adaptation of plants to pathogenic fungi and phytophagous insects

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Parasitoids representing some 15 families of Hymenoptera develop in insect eggs; three of these families, Platygastridae (= Scelionidae), Mymaridae, and Encyrtidae, are associated with Heteroptera. Several species of heteropteran egg parasitoids are or may be important for biological pest control. Successful parasitism of insect herbivores by insect parasitoids arises through several phases of host searching, which lead female wasps to the vicinity of, or in contact with, their hosts. During the host location process, females encounter and explore a variety of stimuli, among which chemical cues (i.e., semiochemicals or infochemicals) play a pivotal role. Female parasitoids are under selection pressure to efficiently invest their limited time on the location and exploitation of host-derived stimuli. In general, the levels of reliability and detectability of a particular stimulus are inversely correlated. Female parasitic wasps adopt differing strategies to solve this dilemma. In this paper we focus on the various host selection strategies employed by heteropteran egg parasitoids and possible means whereby the chemically mediated behavior of these wasps may be exploited to enhance biological pest control.