Compartive Study Of Sex Pheromone Communication Systems Among Tebufenozide And Abamectin Resistant And The Susceptible Strain Of Diamondback Moth, Plutella Xylostella (L.)

Human activities greatly speed up the evolutionary process of many animal species, and one best known example in insect is the the occurrence of insecticide resistance. Insecticide employment may affect the sex pheromone communication systems in pest, along with the evolution of pest resistance to insecticiede. With the high sensitivity and species-specificity, insect sex pheromone communication plays the key role in the reproduction behavior and has been used in pest control and population forecasting. Studes of the changes of sex pheromone communication system between resistant and susceptible pests is helpful for us to control pest more effectively with sex pheromone and to understand the process of speciation. This study comparaed the sex pheromone communication systems of tebufenozid resistant, abamectin resistant and their sussceptible strain in diamondback moth, and investigated the effects of larva treatment with sublethal dose abamectin on the sex pheromone communication system of survival moths. The main results were as following.1. Differences of sex pheromone communication systems in abamectin, tebufenozide resistant and sussceptible strain in diamondback mothCalling behavior of female moths showed that there was no difference in calling rhythm between two resistant and sussceptable females, while the calling percentages of resistant females were much lower than that of the sussceptible females. Analysis of sex pheromone showed that resistant females produced significantly less amounts of sex pheromone, compared with susceptible moths. More impotantly, the ratio of two major pheromone components (Ald/Ac) in Aba-R females was 1.6:8.4, much different from susceptible females (Ald/Ac=4.5:5.5). For the male side, resistant males showed significantly higher EAG responsiveness to female binary sex pheromone mixture (Ald/Ac=1:1) at the dose==1 Ong, and there was no difference between two resistant strains. Resistant males also showed higher EAG response to female binary sex pheromone mixture with ratio 1:9,3:7,7:3 and 9:1 (Ald/Ac) than sussceptible males.2. Wind tunnel and mating choice experiment in abamectin, tebufenozide resistant and susceptible strainWind tunnel experiment indicated that both susceptible and tebufenozide resistant female remaind high attractiveness to three males, with no difference among males of three strains. However, abamectin resistant females suffered low attractiveness to susceptible and tebufenozide resistant males (source contact percentages were 20% and 30%, respectively), lower than abamectin male (35%). The mating choice experiment confirmed that assosiative mating occur between susceptible and tebufenozide resistant strain; however, in susceptible and abamectin resistant strain combination, males of both strains tended to mate with suscaptible female; similarly two resistant male tended to mate with tebufenozide resistant female in abamectin and tebufenozide resistant strains combination. All the results suggest that abamectin female, in which the ratio of two major sex pheromone components was greatly changed, suffer low attractiveness to males and consequently low mating chances. This finding would be very important to the empoyments of’refuge strategy’in pest resistance management, and to the use of insect sex pheromone in pest control.3. Study of sex pheromone communication systems in hybrid F1 of abamectin resistant and susceptible strainThe F1 hybrid offspring Z1 (S(?)×R(?)) and Z2 (R(?)×S (?)) showed similar calling rhythm with their parents. However, the calling percentage and titer of pheromone Z11-16:Ald in females and male’s EAG responsiveness to the bianary pheromone mixture (Ald/Ac=1:1) at different dosages were all between those of two parents, and closer to the mother’s. Another pheromone component Z11-16:Ac was about the same among Z1, Z2 and the resistant strain, but sinificantly higher in the sucsseptible strain. The further analysis of offsprings of Z1×Z2 and the backcrosses will be requried to elucidate the genetics of the insecticide associated changes in sex pheromone communication system in the diamondback moth. 4. Sublethal effect of abamectin on sex pheromone communication systems in susceptible diamondback mothAbamectin treatment with sublethal dose not only extended the larva development and reduced pupa weight, but also affacted the sex pheromone communication system of the survival adults. Calling percentage of survival females reared from larvae treated with sublethal dose of abamectin was significantly lower than that of the control. In agreement, the titers of sex pheromone of treated females were reduced compared with the control females, especially the Z11-16:Ald component. The component ratio (Ald/Ac) was not significant different between treated and control moths. Treatment of larva with sublethal dose abamectin also significantly raised EAG response of males to female binary sex pheromone mixture dosed 1-100ng and at the ratio of 1:1 (Ald/Ac). To other ratioes of the binary sex pheromone mixture (Ald/Ac=9:1,5:5 and 3:7), treated males also showed significantly higher EAG response than control males. The influences on sex pheromone communication system by abamectin of sublethal dose and by the abamectin resistance were very similar, the mechanisms underlying which deservs to be explored.