Preliminary Study On The Basic Immune Response Of R2115 Against Rice Blast

The Indica Hybrid Rice technology,pioneered in our country,has inaugurated a new way for improving the rice yield,and specifically,the research and application of the three-line hybrid rice has made a significant contribution to our country's food security.With the rapid development of economy,people's living standard has been greatly improved.Correspondingly,the dietary structure of people has changed,and the requirement for the quality of food is higher.Therefore,the research for the three-line hybrid rice not only pursues the high yield as before,but also the high quality and the disease resistance.However,rice blast always threatens the safety production of rice in the process of planting,and it also has a serious impact on the yield and quality of rice.Based on this situation,it is the most direct,economical and effective method to select and popularize the disease resistant varieties of rice.R2115 is a high quality rice restorer line created by Huang Fu,the teacher of Sichuan Agricultural University.R2115 has strong disease resistance,good biological characteristics and high competitiveness,which has played an important role in actual production.However,the research on its mechanism of disease resistance is not enough.Therefore,we studied the basic immune process of R2115 against rice blast through the observation of the infection for magaporthe grisea,the accumulation of hydrogen peroxide and the analysis of the expression of related genes in plant protection.The experimental results are as follows:1.The weak pathogenic strain ZB25-GFP and the strong pathogenic strain Zhong1-GFPwere respectively used to infect the living,in vitro and in vitro wound of R2115 leaves.The results showed that there is no obvious lesion phenotype after 7d.Trypan blue staining showed that the spores of rice blast could only germinate and produce germ tubes,not invade the cell when inoculated with ZB25-GFP,but it could form infecting mycelium when the wound is inoculated with the fungus.When inoculated with the Zhong1-GFPfungus,the mycelium was intruded in the leaves,but the growth of the mycelium was inhibited in the later period.2.In order to further observe the infection of Magnaporthe grisea on R2115,the Magnaporthe grisea with fluorescent label was used to inoculate leaf sheath,and the whole infection process was observed using microscope.The experimental results showed that the germination of spores was inhibited effectively before infecting for ZB25-GFP strain,thus the germination rate was significantly lower than that of LTH and other single gene lines,and the ZB25-GFP strain failed to invade the cells normally.However,for the strong pathogenicity strain Zhong1-GFP,the germination of spores was not significantly inhibited in the early stage,and the pathogens could invade cells in the later stage.But the number of pathogens in the cell was a little,and the growth speed of mycelia was slow.3.DAB method was applied to observe the accumulation of H₂O₂.The results showed that the mass accumulation of H₂O₂ in leaves was observed obviously when R2115 was inoculated for 2d.4.OsCPS2,OsKSL,OsCPS4 and OsKSL4genes were functioned as the synthesis of rice husk ketone and PA-PE,and the background expression level of those genes in R2115was higher after inoculated Guy11,simultaneously,the anaphase expression level was also higher than that of LTH.Therefore,when R2115 was infected by rice blast fungus,the phytoalexins rice hull ketone and PA-PE would accumulate quickly,thus inhibited the germination of spore.The above results suggested that R2115 had a higher gene background of phytoalexins rice hull ketone and PA-PE,thus,when infected by rice blast fungus,the gene was induced to express and the corresponding phytoalexins was synthesized.Simultaneously,H₂O₂ was quickly accumulated.Therefore,the germination of the spores was suppressed to prevent the invasion of the rice blast fungus.However,for the virulent strain,the basic immune response of R2115 was not enough to inhibit the rice blast.There should be a strong ETI reaction to impede the infection of Magnaporthe grisea,which requires further research.