Effect Of Silicon On The Physiology And Biochemistry And Molecular Mechanism Of Different Resistance Level Varieties To The Sheath Blight(Rhizoctonia Solani)

There are a large number of studies have shown that silicon can promote plants growth and development, especialy it can enhance the plants’resistance to diseases. The conventional point of view is that the silicon enhanced plants resistance to diseases by the affect of mechanical or physical barrier. But in recent years, some studies have indicated that silicon may be involved in the metabolic processes of plant physiology, induced resistance to the physiological and biochemical response, the activation of plant defense responses, which questioned the traditional concept.The rice variety of Lemont what susceptible to Sheath Blight (ShB) and middle resistant to ShB varity of ZH5was used in this experiment, By using hydroponic rice seedlings, the studies on physiological and biochemical substances changes, effect on the genes expression what related to rice resistance to ShB after inoculation with Rhizoctonia solani with or without silicon application were carried out. The following conclusions were obtained.1、The exogenous of silicon on the silicon content of rice plants and enhanced rice resistance to ShB.Silicon could significantly enhance the resistace level of rice varieties Lemont and ZH5to ShB, Two grades of resistance of Lemont and ZH5to ShB were increased. The silicon contents in Lemont and ZH5plants were significantly increased after artificial application of silicon. The silicon contents in susceptible variety of Lemont increased by10.0%-13.0%, while in the middle resistance variety of ZH5increased by10.2%-10.8%.2、Effect of artiffical application silicon on the physiological and biochemical substances in rice plants realted to the resistance to ShBFor the susceptible variety of Lemont, the artificial silicon application treatment compare with no silicon application, the H2O2contents significantly decreased by20%-50%and MDA content decreased by1.3%-7.0%after inoculation with Rhizoctonia solani,The CAT activity increased by2.0%-51.0%after0-48h inoculation by R. solani, and the LOX activity increased by7.0%-42.0%after24h inoculation. The total soluble phenols and lignin contents in artificial application of silicon were higher than that of no silicon applicion.For middle resistant variety of ZH5, treatments of artificial supply silicon compared with no silicon supply, the contents of H2O2significantly decreased by44.7%-165.0%, MDA decreased by1.3%-7.0%, CAT activity increased by25.7%-45.6%, LOX activity increased by1.64%-19.8%, lignin content increased by14.6%-70.0%. The PAL activity increased by20.3%-66.7%, the PPO increased by43.3%-193.9%after inocated24h-72h inoculation by R. solani. Total soluble phenols content in plants of treatment with artificial supply of silicon is higher than that of no silicon application in the period of0-24h after inoculation by R. solani,For the susceptible variety of Lemont, treatments of artificial supply silicon but no inoculation by R. solani compared with no silicon supply and no inoculation by pathogens, silicon application can promote the growth of rice seedlings. The contents of MDA reduced1.3%-28.0%, the total soluble phenols contents increased by18.0%and17.0%after48h,72h, Respectively. The lignin contents in the plants of silicon application was always higher than that of no silicon supply from0-60h after treatment. The H2O2contents increased by2.1%-20.0%in the0-24h, the LOX activity increased by1.0%-42.0%in the24h-72h, the total soluble phenols contents increased by3.6%-25.0%in12h-24h.For middle resistant variety of ZH5, the H2O2contents increased by11.4%-61.8%in0-24h after treatment, the activity of CAT and LOX increased by3.1%-32.9%,7.1%-34.5%, respectively. The total soluble phenols contents and the lignin content increased by0.3%～17.5%and14.6%-70.0%, respectively. The activity of PAL was significantly enhanced in0-24h after treatment, and the maximum reached557.8μg/ml at24hours after treatment.3、Effect of artificial supply silicon and no silicon application on the expression of related resistance genesTreatments of artificial supply silicon and no silicon application and then inoculation by R. solani The expression of genes Rcht, AOS, NPR and PR4what be related to the resistance was detected by using semi-QRT-PCR technology. The results showed that silicon application could induced and enhanced the expression of rice resistant genes.The expression of most resistant genes in susceptible variety Lemont were stronger than that of in middle resistance variety ZH5. The gene of PAL could express at all time after inoculation in both varieties of Lemont and ZH5, however, the different of expression show no significantly. The expression of gene Rcht in Lemont was significantly enhanced in36h,48h and60h after inoculation by R. solani. The gene’s expression in the treatment of artificial silicon supply was stronger than that of no silicon supply, simultaneity, the expression in variety Lemont was higher than that of in ZH5. The expression of gene AOS in Lemont was stronger than that of gene PAL and all other genes’ expression. The expression of gene AOS began to enhance in the treatment of no silicon supply in36h after inoculation by R. solani. The expression of gene AOS showed no significantly different in ZH5in treatment of no silicon supply after inoculation by R. solani.The expression of genes NPR and PR4in Lemont were significantly stronger than that of in ZH5.Using of FQ-PCR,the genes of PAL, CAT and Rcht in variety of Lemont were firstly raised after inoculation by R. solani in the treatment of silicon supply artificially. The expression of PAL in ZH5was higher than that of in Lemont, the hightest expression, what was the2.1times of artificial silicon supply, woccurred in60h after inoculation by R. solani. The expression of genes CAT and Rcht in variety Lemontwere higher than that of in ZH5. The gene CAT’s expression showed significantly different, the expression in the treatment of artificial silicon supply was 1.5-6.0times than that of no silicon supply. The results also indicated that the expression characters of genes PAL,CAT and Rcht in susceptible and resistance rice varieties were different, and the trends of change also different.