Studies On The Changes Of Cell Wall Degrading Enzymes In Wheat Leaves Infected By Puccinia Striiformis F. SP. Tritici

Several combinations were constructed with different wheat species and stripe rust varieties in this research. The leaves of wheat were collected in different time after inoculated by Puccinia striiformis f. sp. Tritici to extract the cell wall degrading enzymes (CWDE). Activities of CWDE in different combinations were studied by enzyme assay with healthy leaves as control in each combination.In this research, the activities of CWDE were measured by saccharifying according to the theory that red-brown amino compounds were produced when 3, 5-dinitro salicylic acid and aldehyde were heated together. And the testing conditions were made clear. The activity of Cx should be tested with optimal temperature of 50℃, optimal pH of 4.8, incubation time of 30 min, and optimal substrate of 0.6% CMC-Na (w/v). Due to the heat-libality, Cx should be sterilized more than 10 min. The testing conditions of the activity ofβ-G were almost the same with Cx except the substrate of 0.5% salicin (w/v) and the sterilization time of more than 15 min. For PMG, the optimal temperature was 50℃, the optimal pH 4.8, incubation time 1h, and the substrate 0.25% pectin (w/v) with sterilization time more than 10 min. The results of the research showed that activity of CWDE can be detected in both healthy control and inoculation treatment. In different susceptible combination, even though the enzyme activities of healthy control and treatment both changed notably with time, the enzyme activities of treatment were obviously higher than the healthy control from 48 hours to 72h after inoculation (hpi), with the range of 29.6%~79.3% higher than control. Besides, the differences of enzyme activities between control and treatment in the two groups increased to the highest level at 48 hpi or 72 hpi . According to the variance analysis, the differences have significance. This period happened to be the time when haustorial mother cells came into being, which indicated that the secretion of the enzymes had something to do with the haustorial mother cells, and played a certain role when the hypha penetrated the cell wall of wheat. The activity of CWDE had an obvious increase at 168 hpi in the 3 combinations of Mingxian169-CY23, Lovrin13-CY29, and Suwon11-CY31. And the variance analysis showed that this increase had significance. This period coincided with formation of uredospores. Thus the main function of the cellulases in later infection stages may be the utilization of the host cell wall as additional carbon source for the production of uredospores.In the resistant combination of Lovrin13-CY23, the activity of CWDE of treatment was alwayse lower than healthy control which was totally different from susceptible combinations. The big difference between susceptible and resistant combinations also indicated that CWDE might play a certain role in helping hypha penetrating the cell wall of wheat.