Plant Defense Responses Induced By The Salivary Components Of Bemisia Tabaci (Gennadius) B-Biotype (Hemiptera: Aleyrodidae)

With the coevolution of insects, plants have evolved a series of induced defense mechanisms and couldrecognize different types of insects according to the feeding mode, and thus maintaining thedevelopment of their population. The plant responses induced by phloem-feeding insects are one of theimportant part of interactions between insects and host plants. Understanding the plant responsesinduced by phloem-feeding insects will provide a better understanding of plant-insect interactions andnew insights of pest management and the cultivation of pest-resistant plants.Since the introduction of Bemisia tabaci (Gennadius) B-biotype into China in1990s, it has spreadrapidly and broken out in several provinces in China. Because of the wide range of host plants, the B.tabaci B-biotype has gradually replacing the indigenous species Trialeurodes vaprorariorum(Westwood). It is reported that the replacement mechanism between different speciesof whiteflies mainly including asymmetric mating interactions, geminivirus mutual benefit differentpesticides resistance, and so on. Whilefew researched have proved the role of plant defense responsesinduced by B. tabaci in interspecific replacement. Therefore, it is necessary to reveal the physiologicalmechanism of B. tabaci adapting different host plants and its role in displacing T. vaprorariorum. Thesaliva secreted by whiteflies contains many substances involved in plant responses. In order tounderstand the role of the salivary components of B. tabaci B-biotype in the invasion process, weenclose whether the salivary components of B. tabaci B-biotype can induce the plant resistance. B.tabaci B-biotype and Lycopersicon esculentum were chosed and to number of offsprings, transcripts ofkey genes in salicylic acid signaling pathway and the activities of plant protective enzymes weredetected after injection the saliva of B. tabaci B-biotype. The results are as follows:1. The asymmetric effects of plant responses induced by the salivary components of B. tabaciB-biotypeThe saliva of B. tabaci B-biotype was extracted after artificial feeding and injected into tomato leaveswhich were infected by five pairs of whiteflies. We observed the number of offspring to study the effectof local and systemic resistance induced by the saliva of B. tabaci B-biotype on B. tabaci B-biotype andT. vaprorariorum.The results showed that:(1) The saliva of B. tabaci B-biotype can induce local andsystemic resistance which inhibits the growth and development of whiteflies.(2) The effect of plantresponses induced by the salivary components of B. tabaci B-biotype on B. tabaci B-biotype and T.vaprorariorum is asymmetric. This study proved that the salivary components of B. tabaci B-biotypecan induce the plant asymmetric resistance which has a higher negative effect on T. vaprorariorum thantheir own.2. The salicylic acid signaling pathway induced by the salivary componentsTranscripts of PR-1(Pathogenesis-related protein-1)、BGL2(β-1,3-Glucanase)、PAL(Phenylalanineammonialyase) in salicylic acid signaling pathway were detected after injection of the saliva of B. tabaci B-biotype using real-time quantitative PCR. The results showed that: the salivary components ofB. tabaci B-biotype can induce the expression change of key genes PR1、BGL2、PAL in salicylic acidsignaling pathway. The expression of key genes PR1and BGL2increased first and followed withdecrease. The peak level was generally around20h-30h. Moreover, the effect of local induction onactivation of the salicylic acid signal was stronger than that of systemic induction. We can infer that thesalivary components of B. tabaci B-biotype can activate salicylic acid signaling pathway whichinvolved in plant defense response to feeding by B. tabaci B-biotype.3. The tomato protective enzymes induced by the salivary componentsAfter the injection of B.tabaci B-biotype saliva into tomato leaves, activities of plant protectiveenzymes (polyphenol oxidase, peroxidase, catalase and lipoxygenase) at different periods wereanalysized. The results are as follows: the salivary components of B. tabaci B-biotype can significantlyincrease the activities of perxidase, lipoxygenase and catalase. We can infer that the salivarycomponents of B. tabaci B-biotype can induce the change of tomato protective enzymes and conferresistance for plants.