Insecticide Resistance Mechanisms in the Green Peach Aphid Myzus persicae (Hemiptera: Aphididae) II: Costs and Benefits

Background: Among herbivorous insects that have exploited agro-ecosystems, the peach-potato aphid, Myzus persicae, is recognized as one of the most important agricultural pests worldwide. Uses over 400 plant species and has evolved different insecticides resistance mechanisms. As M. persicae feeds upon a huge diversity of hosts, it has been exposed to a wide variety of plant allelochemicals, which probably have promoted a wide range of detoxification systems. Methodology/Principal Findings: In this work we (i) evaluated whether insecticide resistance mutations (IRM) in M. persicae can give an advantage in terms of reproductive fitness when aphids face two hosts, pepper (Capsicum annuum) a suitable host and radish (Raphanus sativus) the unfavorable host and (ii) examined the transcriptional expression of six genes that are known to be up-regulated in response to insecticides. Our results show a significant interaction between host and IRM on the intrinsic rate of increase (rm). Susceptible genotypes (not carrying insensitivity mutations) had a higher rm on pepper, and the transcriptional levels of five genes increased on radish. The rm relationship was reversed on the unfavorable host; genotypes with multiple IRM exhibited higher rm, without altering the transcriptional levels of the studied genes. Genotypes with one IRM kept a similar rm on both hosts, but they increased the transcriptional levels of two genes. Conclusions/Significance: Although we have studied only nine genotypes, overall our results are in agreement with the general idea that allelochemical detoxification systems could constitute a pre-adaptation for the development of insecticid