I would like to discuss the best methods of exposure used to select resistant populations in lab conditions, such as excised leaves (up taking the solution), artificial membrane, dipping technique, or even direct exposure via vial bioassays. I know there is a lot of material covering this on the internet but I would like to hear your personal opinion and experience.
not sure whether or not somebody has selected a resistent strain of sucking sap insects. Try to find out LD50 dose through excised leaves. start with a high dose and then reduce the concentration of insecticides
All these approaches are valid but it depends on the pest species, the host plant and the insecticide. Plus the number of individuals you intend to expose each generation. With any selection experiment, the outcome is going to depend to a large extent on the size and diversity of the gene pool of the pest organism used in your experiment. If it doesn't contain resistance mutations, you are unlikely to see a response.
Hi Muhammad, thanks for your answer. I already have my range of doses that I'm expecting to work in selecting resistant population. I'm also already using the excised leaves bioassays to try to select the population. I just want to be sure if there is another method that could work better for this purpose.
Dear Ian Denholm, all these previous information about the theory are important and I do agree that they are all significant. I'm aware of it. Regarding the techniques available I do no think that they are all valid since the route of exposure is a relevant variable that influences enormously the toxic response caused by the chemical compound. There is non indicative of resistance at field level but some indicative about resistance in lab conditions and it is driving me to speculate about what would be the major differences in resistance at the field and at the lab, knowing that at lab we do not take in consideration the Economic injury level and others variables.
We published a paper many years ago on selection for resistance to azadirachtin in aphids. Have a look at Feng, R and MB Isman (1995) Selection for resistance to azadiarchtin in the green peach aphid, Myzus persicae. Experientia 51: 831-833.
Dear Matheus - Yes, of course the route of exposure is important and has an important bearing on how resistance traits are expressed. If you are aiming to predict likely events in the field, you should simulate as closely as possible the field exposure conditions, though this isn't always the easiest and most practical approach. My gut feeling is that systemic applications are less resistance-prone than foliar ones, but this is complicated by compounds like neonics being used commonly as both systemic and foliar treatments. Exerience at Rothamsted indicates that neonic-resistance selected in whiteflies, aphids and planthoppers (as examples) is generally expressed much more clearly in foliar than systemic bioassays, but if sufficiently potent it can also compromise the efficacy of systemic application at recommended rates. So if you merely want to explore the potential for a pest to resist a toxin, foliar treatments may be more appropriate. If you specifically want to simulate selection pressures imposed by systemic treatments, then you need to deliver the toxin by that means.
Yes I have selected resistant populations of aphids to neonicotinoids
By the name you can make bioassay tests on resistant strains of this insect by field collection of samplesand let it to propgation under field condition for 1 generation
I think Dr. Ian Denholm statements have both theoretical and practical important information regarding my question and I will for sure consider all information above. Thanks you all for your collaboration. Now it is time to continue working on it.
The following link may help you Sir:-
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3694213/
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