Roles Of The Microfilaments In The Interaction Among Wheat And Sphaerotheca Fuliginea, And Puccinia Striiformis F.SP. Tritici

In this study, both the incompatible interaction between wheat cv. ’Suwon 11’ and race of Puccinia striiformis f. sp. tritici （virulent） and the non-host interaction between wheat and Sphaerotheca fuliginea was researched. Inoculated wheat leaves with conidia after injecting the cytochalasin A （CA） into the leaves, injecting water as contrast, and then histochemical studies was done in indicated time points. The production of the hypersensitive reaction （HR）, H₂O₂ and papilla was analyzed histocheically using trypan blue, DAB and coomassie brilliant blue, respectively. The changes of microfilament cytoskeleton have great effect in histocheically reaction in plant-pathogen interaction. The results of the study are as follows:1. The germination and infection processes of the S. fuliginea conidia in host （cucumber） and non-host （wheat） interaction was detected , the haustorium formation of the S. fuliginea conidia on the wheat leaves treated with CA was observed. The results demonstrated that the germination of the S. fuliginea conidia on the wheat was delay and the ratio of the appressorium formation was low contrasting with on the cucumber. moreover, most of the appressoria were abnormal haustorium and could not form second hypha on the wheat. However, the S. fuliginea conidium could invade wheat treated with CA and form mature haustorium, even second hypha. This indicated that whether the actin polymerizing or not is a key factor for the reasone why the pathogen fungi fail in infecting non-host plants.2. Inoculated wheat leaves with S. fuliginea conidia after the leaves were treated with CA, and then the leaf segments were stained by trypan blue, frequency of interaction sites causing HR showed a whole-cell trypan blue staining was microscopically determined. The results demonstrated that the percentage of infection sites with HR increased gradually with time.However, comparing with the contrast, the frequency of infection sites with whole-cell death sustained a lower level and the staining of trypan blue was weaker after the leaves treated with CA. This indicated that the microfilament is essential to cause hypersensitive reaction.3. Inoculated wheat leaves with S. fuliginea conidia after the leaves were treated with CA, the percentage of the infection sites with DAB staining were determined using DAB staining. The results demonstrated that the H₂O₂ accumulation surrounding the penetration sites was significantly suppressed when the microfilament of the wheat leaves was depolymerized. This indicated that the microfilament was concerned with the H₂O₂ accumulation in non-host resistance.4. By coomassie brilliant blue staining, the formation of papilla beneath the infection sites on the wheat was detected, the wheat leaves were treated with CA before the inoculation of the S. fuliginea conidia. The results demonstrated that both CA treated and contrast, the ratio of papilla increased gradually with time. Comparing with the contrast, the percentage of infection sites treated with CA showing papilla accumulation increased slowly with time, and the papilla were not dense. This indicated that the formation of papilla was affected by the depolymerization of microfilament in the resistance reaction.5.The wheat leaves were treated with CA before inoculating wheat strip rust, and treated with evans blue staining and fluorescence stain in indicated time points. The results demonstrated that the HR of mesophyll cells was significantly suppressed when the microfilament of the wheat leaves was depolymerized. This indicated that microfilament might play an important role in wheat vs. wheat strip rust, the polymerization of actin is essential to cause HR.6.The wheat leaves were treated with CA before inoculating , then treated with DAB staining in indicated time points and the percentage of infection sites with DAB staining was determined. The results demonstrated that there was no significantly difference between CA treatment and water treatment in the trend of H₂O₂ accumulation, the percentage of infection sites treated with CA showing DAB staining increased slowly and the DAB staining was weak. This indicated that the polymerization of microfilaments was concerned with the H₂O₂ accumulation in wheat resistance reaction.