| Bemisia tabaci (Gennadius) (Homoptera: Aleyrodidae) B-biotype is a key pest of greenhouse vegetables, ornamental crops, and cotton in many regions of the world and an alien invasive species in China. The host plant species of B. tabaci B-biotype has been increasing with the spreading of its invaded areas. Further, in some areas, such as north China, the competition between B. tabaci B-biotype and its co-existing, closely related species had been observed. The biochemical assay was used to investigate the mechanisms responsible for host plant species increasing of B. tabaci B-biotype and its competition with Trialeurodes vaporariorum (Westwood). The B. tabaci B-biotype and T. vaporariorum were reared on tomato for more than 5 generations, and the activities of detoxifying enzymes (esterases (ESTs), carboxylesterase (CarE) and gluthione S-transferases (GSTs)) were evaluated when both whitefly species were switched on celery, cabbage, cotton, and capsicum plants, respectively. The main results of this study are as follows.The population dynamic investigation indicated that the population density of B. tabaci was much higher than T. vaporariorum on all plant species (P < 0.001). The host preference of 5. tabaci and T. vaporariorum in the field were cabbage > tomato > cotton > capsicum > celery, and tomato > celery > cotton, capsicum and cabbage, respectively.The similar reaction of the activities of ESTs and CarE indicated that CarE was one of the most important enzyme in ESTs responded to plant species switching. The specific activities and the dynamics of activities of ESTs and CarE of the two whiteflies can be significantly affected by switched plant species, and the effects differed from host species and whiteflies, but both related to the preference of host species of the whiteflies. The effects of switched plant species on the activities of ESTs and CarE of whiteflies as well as the activities of ESTs and CarE of whiteflies decreased with the less addict plant species. Both of the whiteflies reacted much faster on addict host species than non-host. The dynamics of ESTs and CarE activities of both were different, and also related to the addiction of plant species of them. On addicted hosts, the activities of ESTs and CarE of B. tabaci B-biotype increased first, and then descended, but the activities decreased all the time when switched on non-addicted hosts. The dynamics of ESTs and CarE activities of T. vaporariorum increased on all plant species.Moreover, the activities of ESTs and CarE of B. tabaci B-biotype reacted much faster to plant species switching than T. vaporariorum. In addition, the effects of plant species switching on ESTs and CarE activities of the two whitefly species were also different between males and females.The activities of GSTs can be enhanced by plant species switching for both whiteflies, but the degrees of the enhancement differed from species and whiteflies. When switched on cabbage and cotton the activities of GSTs were much higher than switched on celery and capsicum, and the acitivities of GSTs of B. tabaci B-biotype was much higher than T. vaporariorum on every host. Both of the two whiteflies reacted faster on hobbies than on non-addicted plants. The activities of GSTs of the two whiteflies reacted the same way when switched on addicted plant species, but they performed differently on non-hosts. The dynamics of GSTs activity of B. tabaci B-biotype were not significantly different on non-addicted plant, the activities of GSTs of T. vaporariorum increased first, and then descended.The present results indicated that the adaptability of B. tabaci B-biotype to plant species switching was more stabilization, faster and efficiency than that of T. vaporariorum, which will be helpful to enhance its adaptability to new plant species and competitive abilities when co-existing with other herbivores.
|
PDF Full Text Request