Ultrastructure, Cytochemistry And Molecular Cytology Of The Interaction Between Wheat (Triticum Aestivum) And Puccinia Striiformis

Wheat stripe rust, caused by the biotrophic pathogen, Puccinia striiformis West, is one of the most important wheat diseases in China and many other countries. The plant resistance has being the most powerful strategy for the disease management and the resistant breeding practice rests mainly on the understanding of the resistance mechanisms. In this paper the ultrastructure, cytochemistry and molecular cytology on the interactions between the pathogen and hosts with different resistance were conducted. The mainly results including:There was great alteration in the ultrastructure of the pathogen in the incompatible interactions. In the intercellular hyphae, the wall staining became darker; its cytoplasm became aggregating and a great amount of fat drops accumulated; At the same times, many vesicles appeared and finally fuse into big vacuole. A number of electron dense granules began to increase in the spaces between the wall and the cytoplasm membrane and in the cell central part. Its mitochondria began to became swollen and degrade into vesicles; All other organelles were also disorganization in the process; The wall became thicker and loosen, and some pores were began to appeared in the wall. The wall degradation was a earlier event to the cytoplasm disorganization.In the incompatible interactions the development of the pathogen haustoria was disorder. The haustoria were found either malformation in its figure and thicken wall, cytoplasm was dark and disorganized gradually, and eventually all the haustorium disappeared, or that they can grow and swell normally in size but the cytoplasm degraded. In the later cases, the cytoplasm aggregated and the organelles degraded into vesicles, fat drops accumulated in it. The size of extrahaustoria matrixbecame larger and great amount fibril deposits accumulated here. Finally, all the haustorium disappeared.In the incompatible interaction, the defense responses were found in the host cells. As contacting with the pathogen hyphae, the host cell walls became dark and dense deposits appeared in it. the plasmolysis occurred in the host cells. The increase of starch granules shown a single peak curve. Most of the organelles remained normal after infection but some cells which direct contact with the hyphae necroses.After the mesophyll cells were infected by the pathogen, their wall became thick strongly around the penetration sites and their staining was more dark, plasmolysis began to become distinct gradually; The chloroplasts became swollen and the starch granules increased with one-peak pattern. More and more callose accumulated around the haustoria. Many organelles such as nuclear, chloroplasts, and endoplasmic reticulum always trended to appeared around the haustorium. The mitochondria became swollen and the cisternae began to disorganize. The degeneration of endoplasmic reticulum was similar to the mitochondria. The vacuole membrane crinkled and broken down. And the cells was dead eventually.There were two different types in the host cell hypersensitive necrosis: the contact-induced and penetration peg-induced. In the contact-induced necrosis, the envelope membranes of chloroplasts remained intact at the early stages but the granum membrane became disorder and indistinct, the stromal membrane broken, then the granum degenerated and the matrix became dense stained. At the later stages, the envelope membrane of the chloroplast broken and the cell became dead. In the penetration peg-induced cells in the resistant hosts, the the envelope membranes of chloroplasts broken at the early stages but the granum membrane became disorder and indistinct, the stromal membrane broken and the contents flowed out, then the stromal membrane broken and the grana became swollen and disorganized, a great amount of vesicles appeared in the cells which eventually broken and the cell necrosed.It was found that the necrosis of the haustoria occurred prior to the host cell necrosis. The host cell hypersensitive response is the outcome or accompanying event of the host resista...