Behavioral Response And Mechanism Of Lysiphlebia Japonica Ashmead To Different Cotton Varieties

Lysiphlebia japonica Ashmead is one of the major natural enemies of aphids, which has significant value in biological control. The food chain of cotton-cotton aphid-L. japonica Ashmead was used and three transgenic cotton varieties (GK12, Xinmian33B and SGK321) and their corresponding conventional cotton (Simian3, Xinmian33and Shiyuan321) were used to study the behavioral pattern of natural enemies. Three treatments, healthy cotton (A), cotton damaged by aphid (B) and cotton damaged by aphid+aphid (C), were designed in the experiments. The effects of the three treatments on the induction and on host-searching behavior of L. japonica Ashmead was studied using Y-tube olfactometer. The reaction of L.japonica Ashmead to the volatile matter released by cotton after being damaged by aphids was also systematically investigated. The components of cotton volatile matter were analyzed and the bioactive component to L. japonica Ashmead was screened by EAG. The main results were as follows.1. L. japonica Ashmead could not distinguish the healthy transgenic cotton from conventional cotton, and the selection rates were both about45%. However, L. japonica Ashmead was tending to the transgenic cotton in treatment B and C, with a selection rate of60%for the transgenic and30%for the conventional. Compared with seven-leaf stage, in the early days of budding and the budding period the attraction of transgenic cotton to Lysiphlebia japonica Ashmead was somewhat enhanced.2. The cotton volatile matters in each treatment were qualitatively and quantitatively analyzed by GC-MS. The results showed that the amount of plant green leaf volatiles such as3-hexanone,2-hexanone and3-hexanol all declined among the major plant volatiles induced by pest damage. For example, in the seven-leaf stage, among the volatiles of Simian3plant, the amount of3-hexanone decreased from276.66±5.67ng/4h in treatment A to145.71±11.6ng/4h in treatment B, and then to73.68±1.48ng/4h in treatment C; the types and amounts of terpene compounds obviously increased compared with the control. Oppositely insect attack could induce the release of3,7-dimethyl-1,3,6-octatriene. The amounts of α-pinene, camphene, β-pinene and β-myrcene released in the treatment B and C were significantly higher than those in the healthy cotton in the control. For example, in the early days of budding, the amount of β-pinene in the plant volatiles of GK12increased to387.63±1.26ng/4h in treatment B, and then to587.17±1.77ng/4h in treatment C from178.19±0.95ng/4h in treatment A.3. The components of the volatiles collected were almost identical in the transgenic and conventional cotton at the same stage and in the same treatment. But there were some differences between different varieties and treatments.1-ethyl-2-methyl benzene was found in Simian3, while not in GK12. Benzaldehyde was collected in the early days of budding and the budding period in Xinmian33B, while not in Xinmian33. There is β-pinene in SGK321, but not in Shiyuan321. The types and amount of the volatiles differed greatly at different stages in the same treatment. The components of cotton volatiles were totally the same in the early days of budding and the budding period. However the components of the two stages were comparatively different with those of the seven-leaf stage. And the release of (E)-2-Hexenal,(E)-2-Hexen—1—ol, α-phellandrene and (D)-citric acid were only detected in the seven-leaf stage; while in the early days of budding and the budding period,3-methyl ethyl butyrate, Benzene,1,3—dimethyl、Heptanal and Pentadecane were released. Individual volatile component behaved differently in various cotton varieties after the plant was damaged.4. Eight active compounds, which could lead to the potential reaction in the antenna of female and male L. japonica Ashmead, were found by EAG Female adults of L.japonica Ashmead could react to the different concentration of seven compounds including Benzaldehyde、β—Pinene、(Z)—3—Hexen—1—ol, acetate、1—Hexanol,2—ethyl—、3,7—dimethyl-1,3,6—octatriene、Decanal and Pentadecane. Male adults could react to the different concentration of seven compounds such as Heptanal、Benzaldehyde、β—Pinene、(Z)—3—Hexen—1—ol, acetate、1—Hexanol,2-ethyl-.Decanal and Pentadecane. The results indicated that the female and male reacted somewhat differently to the components of cotton volatiles.