The Screening And Resistant Mechanism On Sclerotinia Sclerotiorum-Tolerant On Rapeseed Varieties

The stem rot caused by Sclerotinia sclerotiorum is a devastating disease of rapeseed in China.In this study,to determine resistance of 37 rapeseed varieties(Brassica napus L.) from Jiangsu province to S.sclerotiorum,the methods including mycelium inoculation at seedling and flowering stage and oxalic acid infiltration were employed.The consistency of methods was analyzed.Results indicated that tested varieties showed significant difference in resistance to S.sclerotiorum with 4 identification methods,but the similarity level among methods was low.A petiole inoculation method at flowing stage was proposed because it was easy to implement and had higher disease incidence.Eight-three rapeseed varieties(stains) were identified for resistance to S.sclerotiorum by this method.For comparison of ROIs(Reactive Oxygen Intermediates) production and cell death in rapeseed leaves after inoculated with S.sclerotiorum at first,DAB and Evans blue staining were used.Results indicated that the resistant variety Zhongshuang 9 and Wanyou 14 produced less ROIs and cell death than the susceptible variety Huyou 15 and Shilifeng after inoculation with S.sclerotiorum.The pretreatment of rapeseed leaves with antioxidants such as ascorbic acid,catalase made all varieties much more resistant than controls,and H₂O₂ pretreatment increased lesions significantly.It suggested ROIs tolerance is likely one of the resistance mechanisms of rapeseed against S.sclerotiorum.In addition,toluidine bule staining was used to detect the peroxidative incorporation of phenolic compounds into the cell wall.Results showed that the resistant varieties had more peroxidative incorporation of phenolic compounds than the susceptible varieties during the early S. sclerotiorum infection stage.In this study,the leaves of different rapeseed varieties were inoculated with S. sclerotiorum,and the expression of defense genes such as PDF1.2,PR-1,EDS1,Cu/ZnSOD,FeSOD,PAL,nsLTP,GLP was respectively detected by RT-PCR from 0-24 h after inoculation.Results indicated that the interaction of rapeseed and S.sclerotiorum induced the jasmonic acid and ethylene(JA/ET)-dependent pathway,and PDF1.2 was up-regulated.Upregulated expression of EDS1 and downregulted expression of Cu/ZnSOD and FeSOD of resistance varieties after inoculation meant that the hypersensitive(HP) cell death could be decreased.Expression of nsLTP and GLP that were related to cell wall modification was up-regulated after inoculation in the resistant varieties.PAL expression of resistance varieties also increased at 24h after inoculation.EDS1 partial mRNA sequence on rapeseed varieties was obtained.