| The Southern rice black-streaked dwarf virus（SRBSDV）is transmitted by the white-backed planthopper（WBPH）,Sogatella furcifera,in a persistent,circulative and propagative manner.In the last few years,SRBSDV has rapidly spread and caused serious rice losses in China.Silicon（Si）plays an important role in plant nutrition and is considered as a“beneficial substance”or“quasi-essential substance”,which has the function of enhancing plant resistance to insect pests and diseases.Si amendment to plants can confer enhanced resistance to herbivores in many ways,such as strengthening physical and mechanical barriers,reducing digestive efficiency and enhancing indirect plant defense responses.In this thesis,the effects of Si amendment on rice plant resistance to WBPH were clarified,then the effects of Si amendment on transmission of SRBSDV by WBPH and the histological and physiological mechanisms were examined.The results are expected to provide theoretical basis for silicon application in IPM of WBPH and SRBSDV.The principal findings are as follows.1.Effects of silicon amendment to rice on piercing and host selection behaviors of the WBPH.Silicification of rice leaf sheath was observed using scanning electron microscope（SEM）.The piercing behavior of WBPH nymphs was recorded with electrical penetration graph（EPG）.The host selection and oviposition preference of female adults of WBPH were determined with cage test.Compared with the control plants without Si amendment,the rice plants amended with 0.16 or 0.32 g SiO2/kg soil were characterized by increased number of silica cells in the leaf sheaths.Si addition prolonged the non-probing event and pathway event and shortened the phloem ingestion event of WBPH nymphs.In the host selection tests,the settling preference of WBPH female adults for the rice plants amended with0.16 and 0.32 g SiO2/kg soil decreased by 48.0%and 67.4%,respectively,than for the control plants,and the oviposition amount on these Si-amended plants decreased by 34.8%and 46.1%,respectively,than on the control plants.Therefore,Si amendment to rice plants enhances rice resistance to WBPH through increasing the antixenosis of rice to WBPH and impairing the piercing behavior of WBPH.2.Effects of Silicon amendment to rice on transmission of SRBSDV by WBPH.One-step RT-PCR reaction was used to detect the transmission efficiency of WBPH.The piercing behavior of WBPH nymphs was recorded with EPG.Compared with the control plants without Si amendment,the rice plants amended with 0.16 or 0.32 g SiO2/kg soil were characterized by reduced the transmission efficiency and amplification of SRBSDV in rice and WBPH.High Si addition rate prolonged the total duration of non-probing event and shortened the phloem ingestion events（N4-a and N4-b）,significantly reduced the mean duration of N2 waveforms and number of N4-a（>10min）followed by N4-b.The results show that Si amendment to rice plants,through impairment with the virus transmission-related probing behaviors,helps reduce the transmission of SRBSDV.3.Mechanism of silicon amendment to rice affecting the transmission of SRBSDV.Silicification of rice leaf sheath was observed using SEM and silicon content was determined by colorimetry.The callose deposition in leaf sheaths of rice were observed by paraffin section and aniline blue fluorescence staining.The relative expression levels of callose synthase andβ-1,3-glucanase genes were quantitatively detected by real time PCR.In the transmission of SRBSDV,compared with the control plants without Si amendment,the rice plants amended with 0.16 or 0.32 g SiO2/kg soil were characterized by increased number of silica cells,Si content and sieve plates with callose deposition in the leaf sheaths.And in Si amended palnts,expression of callose synthase genes was upregulated and ofβ-1,3-glucanase genes,downregulated.The results show that Si amendment to rice plants intensifies silicification and regulates expression of calloase metabolism genes,which may have contributed to reduced transmission of SRBSDV. |
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