| This thesis reported the results of the study on the host-pathogen relationship of rice blast by using Magnaporthe graea(isolate 70-15) as pathogen and a pair of near isogenic lines (NIL) of rice (C101, resistant to 70-15 and C039, susceptible to 70-15)as hosts, and by means of pathological anatomy and cytochemistry. The results were of useful not only for further study on the invading mechanism of Magnaporthe grisea and resistant mechanism of rice to blast, but also for the cloning and study of rice disease resistant gene, working out the diseases control strategies, developing new fungicides, resistant breeding and varieties screening.Observed under light microscopy, the host (rice) cells of both compatible combination(CO39/70-15) and incompatible one(C101/70-15) did not show any signs of resistant expression, and the germination of conidia, length of germ tubes, number of appressoria were not significantly different before the pathogen(Magnaporthe grisea ) penetrated into the rice leaf tissues. After the pathogens penetrated into the host leaf tissues, however, the situations were quite different between incompatible and compatible combinations. In incompatible combination, the cytoplasm of host cells around the invaded sites concentrated, granulated, turned into brown, died and the growth of the pathogen hypha were restrained intensively. In compatible combination, only few cell cytoplasm concentrated and the concentration were slowly, the growth of pathogen hypha were not significantly restrained, host and pathogen cells kept normal for rather long time.infrastructure observation indicated that the host cell structure were normal, cell wall uniform, membrane and organelles clearly be seen, and no difference between the resistantand susceptible varieties, in un-inoculated control.In the incompatible combination, 1 8h after inoculation, the membrane of resistanthost cell crimpled separated from cell wall, showing typical resistant reaction. Incompatible combination, however, the cells remained normal.40h after inoculation, most of the mitochondria had been seriously injured anddisintegrated in both compatible and incompatible combinations. The chloroplasts werealso injured in some degree, but, the degree of injure on the resistant host was lighter thanon susceptible ones, suggesting that chloroplasts from the resistant host had moreendurance ability than the ones from the susceptible host.H2O2 and peroxidase could be inspected in the wounds, stoma, and penetration sites on both resistant and susceptible host leaf tissues by using DAB staining method.In incompatible combination, H2O2 and peroxidase accumulated quickly at infected sites during initial stage of infection. The staining color on cell wall was darker than the one on cytoplasm, suggesting H2O2 and peroxidase correlated with disease resistance. With the time longer after inoculation, DAB staining extended to the cells adjacent to the infected sites. In compatible combination, DAB staining almost could not be inspected during initial stage after inoculation. However, quantity of H2O2 and peroxidase activities increased significantly 40h after inoculation, but it had few effect on the pathogen hypha growth.The space distribution and activities of peroxidase were analyzed during the interaction between rice and pathogen by means of cytochemical method. The results showed that the peroxidase was mainly localized in mesophyll cell wall and membrane in the intercellular space both in diseased and healthy rice leaf tissues, but its activity was low in the healthy leaf tissues of both resistant and susceptible hosts. Although the peroxidase activity increased in both resistant and susceptible hosts after inoculation, the increase of the activity was much higher in the resistant host than in the susceptible one. On the resistant host, all the cell organalla of infected sites, the adjacent cells and the cellscontacted with pathogen hypha had significant increased in peroxidase activity. On the suscep...
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