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Forming of Cross-Resistance in Housefly (Musica domestica L.) Larvae to biotic and abiotic stressors under selection
M.P.
Sokolyanskaya, G.V. Benkowskaya
Institute of biochemistry and genetics,
Ufa scientific center of RAS.
450054, Ufa, October Prospect, 71,
Russian Federation
The problem of insect resistance to insecticides is old phenomen, which in time attract all greater attention to itself. In literature for the first time this problem was reflected at the beginning XX age, but attracted to itself significant attention by entomologists, chemists, biochemists and the other scientists only with appearance of DDT-resistance in housefly Musca domestica L in 1946 y. (Perry, 1974). If the resistance was uncommon in beginning 50th years, now presence of sensitive populations is uncommon. Besides of that, if firstly observed resistance of one species to one insecticide, presently often one species possesses the resistance to several insecticideses immediately. Additionally insecticide selection can form resistance to such different factors, as heating, cooling, starvation and drying (Tewari, Pandey, 1978), as well as to treatment of formaldehyde, and raised gravitation (Chernysh, Luhtanov, 1985). Resistant to raised gravitation fruit flyes also have the long-time resistance to heating (Minois et al., 1999). Thereby, under influence of insecticides and the other stressors specific and nonspecific, the cross-resistance can be formed in insects.
The housefly is a very convenient object for study for the questions of the resistance forming in laboratory condition. This species has a short cycle of the development (about month), which allows work during the whole year, since well reproducing independently of season of the year. Exactly so we studied the processes of the resistance and cross-resistance forming to different factors used this object.
The studies were conducted on III age larvae of the housefly Musca domestica L. For study of the resistance forming the housefly larvae of the sensitive (S) strain Cooper were divided into groups and each group was selected by the corresponding stress-factor: bithoxybacillin (in concentration from 0,01% in F1 up to 0,19% in F30,the strain RBTB), malathione (in concentration from 0,03% in F1 up to 0,47% in F30,the strain RM), high (from 35°C in F1 up to 64°C in F30, the strain RH) and low (from 15°C in F1 up to 7°C in F30, the strain RC) , temperatures.
The criterion of housefly larvae sensitivity to the preparations was the efficient concentration, led to 50% mortality of individuals (EC50,%), which was defined by the method of probit-analysis (Popov, 1965). The degree of resistance reached in housefly larvae was characterized by the resistance index (RI), which presents itself ratio of resistant strain EC50 to EC50 of sensitive strain (Methodical instructions, 1990).
Results of the evaluating of cross-resistance level in selected strains in 10th, 20th and 30th generations to selectants with toxic action are presented in table 1
Practically all selected strains of the house fly in 10th generation show at least small cross-resistance to BTB, and strain, selected by high temperature - more considerable resistance (RI=13,6). At the same time the cross-resistance level to malathion is small (RI=1,55 and 1,85) or the resistance is absent (RI=0,71 in larvae of the strain RBTB and RI=0,24 in larvae of the strain RH). To 20th generation the cross-resistance increases to this preparation in house flies, selected by BTB and malathion. In flies, selected high temperature the cross-resistance to malathion is increased, but in flies, selected low temperature, the cross-resistance to BTB is increased while cross-resistance to malathion does not change. In 30th generation increase of cross-resistance to BTB observed only in the strain, selected by malathion, while in strains, selected by high or low temperature, occurs certain reduction of cross-resistance to this preparation. Cross-resistance level to malathion does not increase. in all strains in 30th generation.
Direct applying of the probit-analysis method for temperature sensitivity estimation turned out to be difficult. If at treatment by insecticides from different classes (pyrethroids, inhibitors of the chitin syntheses, organophosphorus or organochlorus compounds) or by high temperature it is revealed the proportional dependency of the mortality percent from concentration substance then in the case of the low temperature influence this curve looks like sinusoid. However the certain diapason exists, within of which all explored strains have proportional acute increase of mortality. Under the influence of the high temperatures in our experiment the most rectilinear increase of mortality is registered within from +40ºC to +50ºC. In the variant with low temperatures similar increase of mortality is noted within from +10º before +5ºC.
We offer to use for comparison of different groups of insect, in our case - high and low temperature selected house fly strains, the coefficient of temperature sensitivity (CT), definied as ratio of mortality values in extreme points of the critical temperature rainge for selected strains to the same differences for sensitive, or "basic" strain (Sokolyanskaya et al., 2005).
For such index value 1.0 means absence of some difference in sensitivity to the change of the temperature. If CT value exceeding 1.0, it evidens the decrease of sensitivity (increasing of resistance) at comparing witn basic group of insects; value CT smaller than 1.0 indicates the increase the increase of sensitivity (the reduction resistance). Thereby, it is possible to estimate and compare the results of selection in R-H and R-C strains there (Table 2).
The selected BTB and low temperature strains show similar with sensitive strain attitude to high temperature i.e resistance does not exist. In malathion selected strain the cross-resistance to high temperature developed to 20th generation, which is reducing to very small values in 30th generation. The curve of mortality in selected strains under influence of the low temperatures has, either as in the event of with sensitive strain sinusoid shape. The minimal mortality also was registered under the temperature +10ºC. Thereby the exposure by temperature +10ºC is adaptogenic stress-factor for all selected strains. In 20th generation of all selected strains was observed the low temperature sensitivity lower than in S strain (CT>1) i.e. cross-resistance is formed to low temperature, which is increases to 30th generation, particularly in malathion selected strain. Thereby, malathion selected strain in process of the selection develops resistance not only to selectant, but also cross-resistance to others nonspesific factor.
Proceed from foregoing, we consider that forming of cross-resistance to sharp reduction of the temperature in all strains is indicate of adaptive nature of cold stress that also can be connected with specifics of the influence of the low temperature. Besides, achievement of significant cross-resistance level (5-8-times) in all strains to action of the bacterial preparation BTB is indicative of immune systems activations in strains selected by other factors; spare that proof - an absence of similar level cross-resistance to malathion in these strains i.e. forming to cross-resistance develops by the other mechanism.
REFERENCES
1. Perry A.S. Insecticide resistance in insects and its ecological and economic thrust // Survival in toxic environments. Ed. by Khan M.A.Q., Bederka J.P., Academic Press. - 1974. - P.399-445.
2. Tewari G.C., Pandey N.D. Effect of insecticide resistance on the tolerance to various enviromental stress in rice weevil, Sitophilus oryzae L.// Bull. Grain Technol. 1978. V.16. 1. P. 25-28.
3. Chernysh S.I., Luhtanov V.A. Noncpesific resistance and selection for resistance to insecticides in house fly (Musca domestica) // Zool. J. - 1985. - T.XIV. - V.1. - P.53-60.
4. Minois N., Guinaudy M.-J., Payre F. Le B.E. HSP70 induction may explain the long-lasting resistance to heat of Drosophila melanogaster having lived in hypergravity // Mech. Ageing and Dev. - 1999. - V.109. - N1. - P.65-77.
5. 12. Popov P.V. The Statistical test experienced given by means of regression lines "dose of the pesticides - an activity"// Chemistry in Agryculture. 1965. 10. P. 72-74.
6. 13. Methodical instructions. The Determination of the resistance of vermins of agricul. Crops and zoophages to pesticides. M.:VASHNIL. 1990. P. 9.
7. Sokolyanskaya M.P., Benkowskaya G.V., A.G. Nikolenko A.G. The resistance forming dynamics to different stressors in housefly larvae // Resis. Pest Manag. Nl. - 2005. - Vol.15. - N1.
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