| The brown planthopper, Nilaparvata lugens Stal (Hemiptera:Delphacidae), is a major pest of rice in Southeast Asia and our country. It’s a serious threat to rice production. Chemical pesticides is still the principal means of prevention and treatment of BPH, because of their economic, quick, easy to operate. However, BPH’s own strong resistance and fast mutation lead to chemical pesticides losing efficacy quickly. Extensive chemical pesticides not only pollute the environment, but also can not guarantee the control effect of BPH, then lead to induced resurgence of BPH easily. Therefore, using resistance of host plant will undoubtedly become the most environmentally friendly and economical way to control infestation of BPH and increase rice production potential.Some research shows, abscisic acid (ABA) can improve the ability of plants to resist external violation. We research rice insect resistance through spraying exogenous ABA on insect-sensitive rice TNI and insect-resistant rice IR42 meanwhile inoculating BPH to find the change of callose synthesis and the mechanism of insect resistance in rice. Research on the above questions not only clarifies ABA enhanced rice resistance to insect, define changes of callose synthase and hydrolase but also provides the basis for subsequent further verification. Research on rice resistance to insect from ABA-induced callose formation in the cell wall has important significance on comprehensive management of BPH, it provides the necessary supplement for the previous mechanism of rice resistance to insect and also put forward new theoretical basis for breeding resistant varieties of rice. BPH is regarded as a representative of the piercing-sucking mouthparts insects, the research project will provide reference to comprehensive management of the other piercing-sucking mouthparts insects. The results show as follows:1. Change of rice resistance to insect through spraying exogenous ABA and BPH feedingAfter spraying exogenous ABA and BPH feeding on sensitive rice TN1 and resistant rice IR42, determination of rice plant functional damage index, dry matter weight and yield, we found plant damage index drop significantly, dry matter weight of rice increase significantly compared with the untreated rice plants no matter TN1 or IR42. Compared with controls, the resistance of different rice production declined after heading stage suffered from the harm of BPH’s feeding. While with the increase of the concentration of ABA spraying, the loss of the yield declined. Experiments showed that ABA treatment of rice plants are not suitable for BPH feeding, or ABA increases the resistance of rice plants to BPH, exogenous ABA can reduce rice yield loss at the same time.Determining oviposition and Nlvg gene expression level of females BPH feeding rice, we found that the oviposition of BPH feeding TN1 and were significantly decreased. High concentrations of ABA has a greater influence on the oviposition only when the females feeding TN1, while when the females feeding IR42, the oviposition was very sensitive to the treatment of ABA. High concentrations of ABA has a greater influence on oviposition period only when the females feeding IR42, while when the females feeding TN1, the oviposition period was very sensitive to ABA. The oviposition and oviposition period both were significantly reduced with the increase of concentration of ABA. It shows that different rice varieties after spraying ABA can effectively resist the harm of spawning. Determining Nlvg expression level, the results show that, ABA treatment, the day of BPH feeding all have a significantly effect on the level of gene expression.3-instar nymph of BPH feeding rice treated with ABA, its level of Nlvg gene expression decreased significantly when the nymph eclosion. It shows that ABA can reduce the fertility of BPH.2. Change of the contents of rice callose through spraying exogenous ABA and BPH feedingDetermining the callose contents in rice which treated with exogenous ABA and fed by 3-instar nymphy of BPH, the results shows that the callose content increase. And the content is different due to different rice varieties, while it has less different involved in the organ of rice. Compared with the control (without ABA treatment), the callose contents of root and leaf sheath of TN1 were not significantly change. While IR42 is different, when treated with 20 and 40 mg/L ABA, the callose contents of roots increased by 100.3% and 237.9%, respectively, and the leaf sheath significantly increased by 140.1% and 140.1%, respectively.Callose is controlled by callose gene, there are 10 callose synthase genes(OsGSL 1, OsGSL 2, OsGSL 3, OsGSL4, OsGSL 5, OsGSL 6, OsGSL 7, OsGSL 8, OsGSL9, OsGSL 10), and 6 hydrolase genes(Osg 1, Gns 2, Gns 3, Gns 4, Gns 5, Gns 6). Determining the gene expression level, we found Osg 1 only expressed in susceptible rice variety (TN1). We used fluorescent quantitative analysis to filter callose synthase and hydrolase gene. Both rice varieties with BPH feeding showed higher expression of callose synthase gene after ABA treatments. After 1 d feeding of BPH, the callose synthesis of sensitive variety (TN1) has been reduced and the resistant variety (IR42) itself can increase the synthesis of callose. The exogenous ABA can increase the synthesis of callose in both susceptible variety (TN1) and resistant variety (IR42). After 2 d feeding of BPH, the expression of callose synthase gene still increased, but IR42 showed a downward trend. So exogenous ABA has a longer effect on TN1 than IR42. The callose hydrolase of TN1 is more easily to be degraded than IR42 and the exogenous ABA can reduce the degradation of callose in TN1 significantly. |
