| Bemisia tabaci biotype B is an important invasive insect pest, Trialeurodes vaporariorum and Myzus persicae are also important agricultural insect pests, all of them are phloem sap-sucking insects and share many host plants. Our previous research showed that B. tabaci pre-infestation could induce the defense against M. persicae in systemic leaves of tobacco plants, but not in local leaves, and the defense was related to salicylic acid(SA)pathway of host plant induced by B. tabaci. In this research, the secondary compounds and defense enzymes which specifically induced by B. tabaci were screened by determining and analyzing the differences in biochemical changes induced by the three phloem sap-sucking insects based comparing the differences in defense against M. persicae induced by their infestation. The defense compounds against aphids were further screeninged by combining their space-time expression, changes in transgenic tobacco and the results of defense against M. persicae. This research had important academic meaning for showing competitive replacement mechanism of B. tabaci to other native insects. Major research results as follows:1. Bemisia tabaci nymphs’ infestation induced intense systemic defense against M.persicae, T. vaporariorum nymph take second place, both whitefly adults and M. persicae infestation didn’t affect M. persicae obviously. Compared control, in systemic leaves, B.tabaci nymph infestation induced 64.4% decrease of aphid survival, 9.9 nymphs/female decrease of fecundity, 1.6 d increase of development and 0.23mg/ aphid decrease of average weight, all of them differed significantly from control; T. vaporariorum nymph infestation just induced 16.7% decrease of aphid survival and 0.13mg/ aphid decrease of average weight,they also differed significantly from control, but aphid fecundity, development had no obvious differences with control; both whitefly adults and M. persicae infestation didn’t affect the aphids obviously.2. All of adults and nymphs of both whitefly species and M. persicae could induce significant increase of SA content, but the changes have obvious differences, B. tabaci nymph induced the most intense change of SA content. B. tabaci nymph induced SA content increased 19.1- and 10.2-fold in local and systemic leaves, respectively; T. vaporariorum nymphs infestation induced SA content increased 4.4- and 2.3-fold, respectively. SA content changes induced by adults of both whitefly species were significantly lower than those caused by their nymphs, B. tabaci adults induced SA content increased 4.8- and 1.0-fold in local and systemic leaves, respectively; T. vaporariorum adults induced SA content increased 1.5-fold in local leaves, whereat it didn’t change SA content in local leaves. SA content in local and systemic leaves of aphid infested plants just increased 3.0- and 1.2-fold, respectively. SA content changed in time and space in B. tabaci adults infested plants: The 1st, 2nd, 3rd and 4th B. tabaci nymph infestation induced 0.2-, 10.2-, 1.1- and 0.2-fold increase of SA content in systemic leaves, respectively, the most intense increase was induced by the 3rd nymphs; SA content in local, systemic and unexpended leaves of B. tabaci nymph infested plants increased 19.1-,10.2- and 4.7-fold, respectively, it decreased from down to up. Combined with the results of defense against aphids, it showed that SA contents induced by the three insect species were positively correlated with defense against M. persicae.3. Comparison of six defense enzyme activity changes in tobacco leaves induced by the three insect species showed that peroxidase(POD), β-1,3 glucanase, catalase(CAT) and chitinase activity was specifically induced by B. tabaci nymph infestation, and β-1,3glucanase, CAT and chitinase were related to the defense against M. persicae. β-1,3 glucanase,CAT and chitinase in systemic leaves specifically induced by B. tabaci, they were 1.91-, 1.46-and 1.46-fold of control, respectively, and changed more significantly than that in local leaves;their changes induced by T. vaporariorum nymphs were obviously lower than B. tabaci nymphs induced, were 1.30-, 1.30- and 1.09-fold of control, respectively; M. persicae infestation have no obvious effect on the three defense enzyme activities. The maximum change levels of aascorbate peroxidase(APX), polyphenol oxidase(PPO) and POD in T.vaporariorum nymphs and M. persicae infested plants were higher than the systemic leaves of B. tabaci nymph infestated plants. Combined with the results of the three insect species induced defense against aphid, it showed that β-1,3 glucanase, CAT and chitinase were positively correlated with defense against M. persicae.Further studies showed that, Nah G tobacco inhibit the increase of β-1,3 glucanase, CAT and chitinase activities induced by B. tabaci nymph; β-1,3 glucanase, CAT and chitinase activities induced by B. tabaci nymph in wild tobacco changed in time and space, the most intense increase incident in the 3rd nymph infested plants; in local, middle, systemic and unexpended leaves of B. tabaci nymph infested plants, the maximum increase of the three enzymes activities incident in systemic leaves. Combined with the results of B. tabacinymph induced defense against aphid, it showed that β-1,3 glucanase, CAT and chitinase were closely related to defense against M. persicae, whereas APX, PPO and POD had no obvious relationship with it.4. The total number of B. tabaci nymph affected compounds detected by HPLC was3597 compared with control, and the number of increased and decreased was 2442 and 1155,respectively. In the 2442 compounds, B. tabaci nymph induced special increase of 44 compounds, and induced over 5-fold increase of 26 compounds compared with T.vaporariorum nymphs infested plants. Combined with the results of two whitefly species induced defense against aphid, it showed that there were 11 compounds were related to defense against aphid. Next, compared the changes of the 11 compounds induced by B. tabaci nymph in Nah G and wild tobacco, it showed that Nah G tobacco inhibited the increase of the11 compounds contents, combined with the results defense against aphid, we speculated that they may play role in B. tabaci nymph induced defense against aphid.5. Comparison of secondary compound content changes in tobacco leaves induced by the three insect species showed that chlorogenic acid, catechuic acid, caffeic acid, p-counaric acid,rutin, scopoletin, ferulic acid and quercetin was specifically induced by B. tabaci nymph infestation, and chlorogenic acid, catechuic acid, caffeic acid and rutin were related to the defense against M. persicae. chlorogenic acid, catechuic acid, caffeic acid and rutin in systemic leaves specifically induced by B. tabaci, they were 4.00-, 2.84-, 1.87- and 3.81-fold of control, and changed more significantly than that in local leaves; their changes induced by T. vaporariorum nymphs were obviously lower than B. tabaci nymphs induced, were 2.27-,2.13-, 1.32- and 3.19-fold of control, respectively; M. persicae infestation didn’t cause the increase of the four secondary compounds. p-counaric acid, ferulic acid, scopoletin,kaempferol and quercetin increased more intense in local leaves of B. tabaci nymphs infested plants than in systemic leaves; T. vaporariorum nymphs infestation just induced kaempferol and quercetin increased in local leaves; whereas M. persicae infestation had no obvious effect on the five secondary compounds content. Combined with the results of the three insect species induced defense against aphid, it showed that chlorogenic acid, catechuic acid, caffeic acid and rutin were positively correlated with defense against M. persicae.Further studies showed that, Nah G tobacco inhibit the increase of chlorogenic acid,catechuic acid, caffeic acid and rutin content induced by B. tabaci nymph; chlorogenic acid,catechuic acid, caffeic acid and rutin content induced by B. tabaci nymph in wild tobacco changed in time and space, the most intense increase incident in 3rd nymph infested plants; in local, middle, systemic and unexpended leaves of B. tabaci nymph infested plants, the maximum increase of the four secondary compounds content incident in systemic leaves.Combined with the results of B. tabaci nymph induced defense against aphid, it showed that chl orogeni c acid, catechui c acid, caffei c acid and r uti n were cl osel y relat ed t o defense against M. persicae, whereas p-counaric acid, scopoletin, ferulic acid and quercetin had no obvious relationship with it. |
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