The Correlation Of Rice Black-streaked Dwarf Disease And Plant Hormones And Cultivation Of Resistant Varieties

Rice is one of the most important crops worldwide, and is a major cereal cropthat provides food for almost half the world population. China, as to be the largest riceproducing country in the world, it is also one of the world’s biggest rice consumptioncountries. Therefore, the rice yield and quality have become important factors in thesustainable development of our conutry and national economy. Rice black-streakeddwarf disease (RBSDD), caused by rice black-streaked dwarf virus (RBSDV), is akind of serious viral disease in temperate rice-grown areas. It has been suggested thatthe virus usually leads to severe rice growth abnormalities, such as severe dwarfing,more ineffective tillerings with almost no heading, which has made enormous threatto food safty and people health of our countryIn order to reduce the damage of RBSDD to the grain production, we carried outcomprehensive analyze about pathogenesis. Using normal and RBSDV infected riceas materials, we carried out paraffin sections and microscopic observation of differenttissues of rice, and the chitinase activity was determined, and further measured thecontents of plant hormones such as ABA, IAA and GA and so on by ELISA method.Through the investigation, the results indicated that the cells of RBSDV infected ricetissues are short and smaller than those of healthy rice, and the phloem cells arrangedin the infected rice stems are slightly disorder, which may lead to the abnormaldevelopment of vascular system, which may be one of the cause of plant dwarfing. InRBSDV-infected rice, the chitinase activity increased significantly, is2.7times ofnormal plants.The contents of ABA, IAA increased, and the GA content decreased,which indicated that the pathogenesis-related protein and plant hormones may playimportant roles in plant defense responses during virus infected process, but thespecific mechanism remains to be further research. In order to get deep understanding of RBSDD, the method of high-throughputsequencing was also adopted to analysis gene expression patterns of healthy andinfected rice samples. The sequencing results combined with GO functionalenrichment analysis, expression pattern clustering, and pathway significantenrichment analysis, about192differentially expressed genes were obtained, amongwhich there are11genes encoding cytochrome P450s,28genes related to defense andstress, and12genes related to photosynthesis. Meantime, the genes of differentiallyexpressed which belong to biosynthesis pathways of secondary metabolites take a bigpart of all varied genes. At the same time, the qRT-PCR was carried out and partiallydifferentially expressed genes were verifed. The validation results demonstrate thatthe expression level of these genes changed significantly. The prelimary resultsindicated that the datas derived from high-throughput sequencing were genuine andbelievable.RNA interference (RNAi), as a newly developed tool of antiviral geneticengineering of plants. In this research,7pairs of RBSDV specific primers weredesigned according to the RBSDV sequences. After obtaining the interferencefragements and construction of the interference vectors using modified pUC19separately, the complete interference fragments were further digested and integratedinto the modified pCAMBIA1300vector which was using ubiquitin as promoter andbar gene as selectable marker. The transgenic rice seedlings were obtained byagrobacterium-mediated transformation to rice variety of Shengdao13, and partiallypositive transgenic rice seedlings were harvested．This work will provided candidatematerials for the innovation of germplasm for rice black-streaked dwarf virusresistance.In summary, the aim of our research is to resolve the major problems of ricediseases, especially rice black-streak dwarf disease, which were happened frequentlyin Huanghuaihai rice production area. These results could aid in research into newstrategies to protect cereal crops against viruses, and reveal the molecular mechanismsof development of specific symptoms in RBSDV-related diseases. At the same time,the positive transgenic rice seedlings by RNAi technology were havested. And the disease inoculation and resistant abilities of both transgenic materials will all beanalyzed in the field and laboratory further, in the hope that to improve the yield andquality of rice.