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.


RESULTS
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 (r(m)). Susceptible genotypes (not carrying insensitivity mutations) had a higher r(m) on pepper, and the transcriptional levels of five genes increased on radish. The r(m) relationship was reversed on the unfavorable host; genotypes with multiple IRM exhibited higher r(m), without altering the transcriptional levels of the studied genes. Genotypes with one IRM kept a similar r(m) on both hosts, but they increased the transcriptional levels of two genes.


CONCLUSIONS
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 insecticide resistance. Genotypes carrying IRM exhibited a higher r(m) than susceptible genotypes on radish, the more unfavorable host. Susceptible genotypes should be able to tolerate the defended host by up-regulating some metabolic genes that are also responding to insecticides. Hence, our results suggest that the trade-off among resistance mechanisms might be quite complex, with a multiplicity of costs and benefits depending on the environment.
Instituto de Ciencias Ambientales y Evolutivas, Facultad de Ciencias, Universidad Austral de Chile, Valdivia, Chile.
Andrea X
AX
Silva
Leonardo D
LD
Bacigalupe
Manuela
M
Luna-Rudloff
Christian C
CC
Figueroa
D000222:Adaptation, Physiological / Q000235:genetics; D000818:Animals; D001042:Aphids / Q000235:genetics* / Q000502:physiology; D002212:Capsicum / Q000469:parasitology; D002219:Carbamates / Q000494:pharmacology; D043182:Carboxylesterase / Q000235:genetics; D002401:Cathepsin B / Q000235:genetics; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics; D019143:Evolution, Molecular; D005786:Gene Expression Regulation / Q000187:drug effects / Q000235:genetics*; D005838:Genotype; D005982:Glutathione Transferase / Q000235:genetics; D018840:HSP70 Heat-Shock Proteins / Q000235:genetics; D058507:Host Specificity / Q000235:genetics; D006801:Humans; D019476:Insect Proteins / Q000235:genetics; D007305:Insecticide Resistance / Q000235:genetics*; D007306:Insecticides / Q000494:pharmacology; D007527:Isoenzymes / Q000235:genetics; D009154:Mutation; D027861:Prunus / Q000469:parasitology; D011743:Pyrimidines / Q000494:pharmacology; D031224:Raphanus / Q000469:parasitology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015854:Up-Regulation / Q000187:drug effects
D002219:Carbamates; D018840:HSP70 Heat-Shock Proteins; D019476:Insect Proteins; D007306:Insecticides; D007527:Isoenzymes; D011743:Pyrimidines; C011994:pirimicarb; D003577:Cytochrome P-450 Enzyme System; D005982:Glutathione Transferase; D043182:Carboxylesterase; C111206:FE4 protein, Myzus persicae; D002401:Cathepsin B