Behavioural differences during host selection between alate virginoparae of generalist and tobacco-specialist Myzus persicae (original) (raw)
2005, Entomologia Experimentalis Et Applicata
Host plant selection and acceptance by aphids involves four consecutive steps: (1) prealighting behaviour, (2) leaf surface exploration and probing of subepidermal tissues, (3) deep probing of plant tissues, and (4) evaluation of the phloem sap. Host specialisation in aphids may involve not only different performances on potential hosts, but also different strategies for host selection and acceptance. Myzus persicae s.s. (Sulzer) (Homoptera: Aphididae) is one of the most polyphagous aphid species, although a tobacco-adapted subspecies, M. persicae nicotianae, has been described. These two taxa constitute a good system for studying the effect of host range on host selection strategies. We studied the first two steps in the host selection process by alate virginoparae of M. persicae s.s. and M. persicae nicotianae on host and non-host plants, using three types of behavioural assays: wind tunnel, olfactometry, and video-recording. Alate virginoparae of M. persicae nicotianae recognised and chose their host plant more efficiently than M. persicae s.s., on the basis of olfactory and visual cues, and factors residing at cuticular and subcuticular levels. Host recognition was evident before phloem tissues were contacted. Olfactory cues were apparently not involved in host selection by M. persicae s.s.
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Decision-making during host selection by phytophagous insects has proved to be related to host range, with specialists taking faster decisions than generalists; however, this pattern fails to materialize in some host selection studies performed with aphids. Differences found in testing designs point to rearing effects on aphid host selection. To test whether specialization patterns derive from the nature of the aphid or as a consequence of rearing environment, host selection behaviours were compared between the generalist Myzus persicae (Sulzer) s.s. and its subspecies specialized on tobacco when reared on a common host and offered the choice of an alternative host and a non-host plant. Pre-alighting (host finding and attraction towards host volatiles) and post-alighting (leaf surface exploration and probing) behaviours did not differ between the generalist and the tobacco-specialist, except in the allocation of time to probing behaviour; furthermore, all specialists chose the host on which they performed best. Thus, although the specialist was not faster than the generalist, it showed a higher level of commitment to its preferred host plant.
Morphological variation of insect population in relation to the different host plants is an important phenomenon that leads to ecological specialization. In this study, we describe the morphological variation of Myzus persicae (Sulzer) (Homoptera: Aphididae) individuals on field samples collected from five different host-plants namely- Solanum nigrum, Calotropis procera, Brassica oleracea, Brassica rapa campestris and Raphanus sativus, from different localities in District Kushinagar of Uttar Pradesh, India with similar climatic conditions. Sixteen morphological characters were measured in 50 wingless aphids collected from plants of the five host species. A significant difference was observed in length of antennal segment IV and VI base, body size, midfemur, hindfemur, u.r.s., siphunculi and of cauda. Results demonstrated that the morphology of Myzus persicae was affected by its host plants.
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