甘蓝对B和Q型烟粉虱非对称性影响及其机制

Whitefly Bemisia tabaci Q biotype is the dominant biotype in wild field in China. It is generally accepted that Q whiteflies are more tolerant to most host plants than B. In contrast, cabbage Brassica oleracea is one of the rare host plants which have been reported to be more suitable to B than to Q, the asymmetric effects and mechanisms of cabbage to B and Q are poorly explored. We use the GC-MS analysis to determine the differences in chemical compositions and contents of volatile terpenoids released from cabbage damaged by B and Q, respectively, and compare the influences of previously damaged cabbage on host selection, oviposition preference and EPG feeding behavior of the subsequent B and Q whiteflies. At the same time, we employ HPLC and LC-MS analysis to investigate the differences in chemical compositions and contents of main induced glucosinolates from cabbage damaged by B and Q, respectively. We further employ artificial diet method to determine the differences of main glucosinolates induced by B and Q on feeding behavior, glucosinolates secretion and the gene expression of main detoxification enzymes between B and Q. From the points of behavior, molecular and physiology, we aim to elucidate the asymmetric effects and mechanisms of cabbage to B and Q whiteflies, which may shed some light on Q whiteflies control.

Q型烟粉虱是当前我国田间主要危害生物型。Q型烟粉虱对绝大多数寄主植物的适应能力通常强于B型烟粉虱。甘蓝是目前已报道少有的有利于B而不利于Q型烟粉虱的寄主植物，其对B和Q型烟粉虱非对称影响机制还不甚清楚。我们采用GC-MS分析甘蓝分别受B和Q型烟粉虱取食为害后诱导产生的挥发性萜类化合物化学成分和含量差异，比较烟粉虱前期取食危害的甘蓝对后续烟粉虱寄主选择、产卵和EPG取食行为的影响。同时，我们采用HPLC和LC-MS分析B和Q型烟粉虱危害后的甘蓝诱导产生的主要芥子油苷化学成分和含量，进一步采用人工饲料方法测定甘蓝受害后诱导产生的主要芥子油苷对B和Q型烟粉虱取食行为、芥子油苷的分泌和主要解毒酶基因表达的差异，从行为、分子和生理角度阐明甘蓝对B和Q型烟粉虱非对称影响及其机制，研究结果可望为Q型烟粉虱的防治提供理论依据。

B和Q烟粉虱是两种重要外来入侵害虫，给园艺作物生产带来重大损失。我们前期研究发现B烟粉虱喜好甘蓝，而Q烟粉虱不喜好甘蓝，为了阐明甘蓝对两种烟粉虱的非对称影响及其机制，我们从甘蓝主要营养和次生抗虫物质差异、受害后诱导防御差异及EPG取食行为差异三方面开展研究。采用室内选择实验测定B和Q型烟粉虱对未受害5个甘蓝品种及分别受两种烟粉虱危害后甘蓝的取食和产卵选择性，发现甘蓝叶片中多酚含量介导两种烟粉虱的取食和产卵选择性，而不是由甘蓝叶片中主要营养和硫甙介导的。甘蓝受B危害后，叶片中酚类及其合成基因表达上升，而Q烟粉虱能操纵寄主植物的防御反应，不会导致多酚及其合成基因表达升。我们进一步生测寻找确定哪种酚类活性最高，发现每种酚类对烟粉虱致死率差别不大，可见，甘蓝对烟粉虱的不利影响归因于总酚含量，并不是哪一种特殊的酚类。我们采用EPG测定了B和Q烟粉虱在甘蓝上的取食行为，发现B和Q烟粉虱持续取食甘蓝6小时，它们刺破细胞百分率没有显著差异, 刺破细胞总停留时间和刺破细胞总次数都没有显著差异，但Q烟粉虱平均每次刺破细胞停留的总时间显著长于B烟粉虱。可见Q暴露在硫甙水解有毒产物面前风险大于B。总之，甘蓝受害后诱导防御及B和Q烟粉虱取食行为（刺破细胞）差异介导甘蓝对B和Q的非对称影响。