B型烟粉虱对寄主转换的适应性

将B型烟粉虱分别从嗜性较强的番茄上转移到嗜性相对较弱的国抗22棉花、泗棉3号棉花和辣椒上, 以及从嗜性较弱的辣椒上转移到嗜性相对较强的番茄、国抗22棉花和泗棉3号棉花上, 观察寄主转移后的F₁代、F₂代、F₃代烟粉虱产卵效应和寄主适应度的变化;将F₄代烟粉虱再转移到原寄主, 观察烟粉虱产卵效应和寄主适应度的恢复情况。结果表明, 烟粉虱在不同嗜性寄主上的产卵效应存在明显的差异。在不同嗜性的寄主之间转移, 烟粉虱的寄主适应度变化趋势不同, 从嗜性较强的寄主转移到嗜好性相对较弱的寄主上, 烟粉虱的寄主适应度迅速下降;从嗜性较弱的寄主向嗜性较强的寄主转移后, 烟粉虱的适应度则会迅速提高。烟粉虱对新寄主的适应速度与其对原寄主和新寄主之间的嗜性差异程度有关, 但一般经过1-2个世代后, 产卵效应会逐渐恢复到烟粉虱在该寄主上的正常水平。从过渡寄主转移到原寄主, 烟粉虱的寄主适应度变化符合一般的寄主转移规律, 但嗜性相对较强的过渡寄主可以刺激烟粉虱提高寄主适应性。

Adaptability of B-biotype Bemisia tabaci (Gennadius) to Host Shift

The spawning ability and host adaptability of B-biotype Bemisia tabaci were measured in F₁, F₂, and F₃ generations after being transferred from its preferred host, tomato, to the low-preference hosts cotton (cultivars Guokang 22 and Simian 3) and capsicum. We also evaluated its spawning and adaptability after transfer from capsicum to tomato and the two cotton cultivars. B. tabaci adults in the F₄ generation produced on new hosts were transferred back to the original host plants, and the recovery of their spawning ability and their host adaptability were examined. The results showed significant differences in the spawning ability of B. tabaci among six host plants: capsicum, Simian 3 cotton, Guokang 22 cotton, tomato, Abutilon theophrasti, and eggplant. The spawning ability on these host plants, from greatest to least, was as follows: tomato > velvetleaf > eggplant > GK22 totton > S3 cotton > capsicum. After being transferred from the preferred host, tomato, to low-preference hosts (GK22 cotton and S3 cotton, and capsicum) the spawning ability of B. tabaci adults in the F₁ generation decreased by 23.9, 58.7, and 41.3%, respectively, and the host adaptability decreased by 40.5, 44.3, and 54.2%, respectively. The spawning ability and host adaptability gradually increased in successive generations. However, there were no differences in the host adaptability between the F₂ and F₃ generations, indicating that B. tabaci adapted to the new host after the F₂ generation. After transfer from the low-preference host, capsicum, to tomato, GK22 cotton, and S3 cotton, the spawning ability of B. tabaci adults in the F₁ generation increased by 23.7, 17.8, and 25.8%, respectively, and the host adaptability increased by 103.07, 36.4, and 59.1%, respectively. The spawning ability and host adaptability leveled off in successive generations. After transfer from capsicum to the other three hosts, the spawning ability and host adaptability in the same generation was consistent with the original preferences of B. tabaci towards these hosts. We evaluated B. tabaci adults in the F₄ generation that had originally been transferred from tomato hosts to the three other host plants (bridging hosts) and then back to the original host, tomato. In the F₁ generation, the spawning ability greatly increased. However, with successive generations, the spawning ability decreased slightly and then leveled off. After transfer from the bridging host back to tomato, the host adaptability gradually increased. When GK22 and S3 cotton were used as bridging hosts, the host adaptabilities of the F₂ and F₃ generations were significantly greater than that of the F₁ generation. When capsicum was used as bridging host, the host adaptability of the F₃ generation was significantly greater than those of the F₁ and F₂ generations. We also evaluated B. tabaci adults in the F₄ generation that had originally been transferred from capsicum to the other three hosts and then back to capsicum. The spawning ability markedly decreased in the F₁ generation, then increased in the F₂ generation and leveled off in the F₃ generation. The host adaptability of B. tabaci adults that were transferred from the three bridging hosts to the preferred host, tomato, was higher than that of B. tabaci adults retained on the original host. After being exposed to the cotton bridging hosts (GK22 and S3), the host adaptability increased by 19.8 and 25.2%, respectively. After exposure to tomato as the bridging host, the host adaptability of B. tabaci increased by 30.5%. These results indicate that strong bridging hosts can stimulate the host adaptability of B. tabaci.