Physiological And Biochemical Analyses Of Resistance Of Different Rape Varieties To Sclerotinia Sclerotiorum

Sclerotinia stem rot is an important disease on rapeseed, in order to further explore thepathogenic mechanism of S. sclerotiorum and the resistance mechanism of differentrapeseed varieties to S. sclerotiorum, we chose two resistant varieties Zhongyou821,Deyou5and two susceptible varieties Wanyou14, Zayou1as experimental materials, theleaves were inoculated with different virulence of S. sclerotiorum isolates and treated withoxalic acid at the seedling stage, detached leaves were inoculated with S. sclerotiorum atthe flowering age, the variation of physiological and biochemical indicators in the leaveswere analyzed, the results are as follows:Identification of selected rape varietie’s resistance and the chose of oxalic acidconcentration: using the inoculation of detached leaves and analyzed, further determinedthe resistance of the tested rapeseed varieties (Brassica napus L). Four varieties of rapeleaves were treated by different concentrations of oxalic acid, they were5,10,15mmol/Lrespectively,10,15mmol/L concentrations of oxalic acid damaged a lot, most of the leavesof Zhongyou821and Deyou5turned yellow, the leaves of Wanyou14and Zayou1werebegan to decay, and the measurement and analysis of the indicators were affected, the5mmol/L was chosen as used in this experiment.Physiological and biochemical indicators of seedling rape after treatment: the contentof MDA in four species of rape was a little difference when unvaccinated, resistant andsusceptible material’s MDA content were increased after inoculation, but the MDA contentof susceptible varieties were significantly higher than that of resistant varieties, and theincreasing amplitude was large. The content of Pro in resistant varieties was higher thanthat in susceptible varieties when unvaccinated, both were increased after inoculation, butresistant varieties were significantly higher than susceptible varieties. Soluble sugarcontent increased at first and then decreased, susceptible varieties rose significantly higherthan resistant materials. The content of SP reached a minimum value in resistant varieties24hours after inoculation,48hours reached a maximum value, and then decreased buthigher than the control, the content of SP in susceptible varieties reached a maximum value24hours after inoculation and then decreased.Physiological and biochemical indicators of flowering age of rape after inoculation:the content of MDA were increased both in resistant and susceptible materials afterinoculation, but susceptible varieties increased faster accumulated more, significantlyhigher than that in resistant varieties. Strong pathogenic strain NG4induced more MDA than weak pathogenic strain WW2. This result was consistent with the seedling stage. Theactivity of CAT was showing a trend that decreased first and then increased both inresistant and susceptible varieties after inoculation, resistant varieties were higher than thatof susceptible varieties and consistently lower than that of control, resistant varietiesdecreased greatlyand susceptible varieties decreased with small change ranges. Strongpathogenic strain NG4induced the reduction of CAT activity in a larger change range thanthan weak pathogenic strain WW2and reached significant difference. PAL activity of theresistant and susceptiblevarieties were both increased and then decreased after inoculatedwith strong pathogenic strain NG4, resistant varieties produced two wave crests,susceptible varieties change slightly. PAL activity in resistant varieties increased earlierthan susceptible varieties,accumulated more. PAL activity of all four varieties showed atrend of increased and then decreased after induced with weak pathogenic strainWW2, butthe rate of increase in resistant varieties was greater than susceptible varieties. It explainedthat there were different resistance mechanisms of different resistant varieties of oilseedrape to strains of different pathogenicity. Chitinase activity of all varieties increased afterinoculation, resistant varieties rise faster and last for a longer time than the susceptibleones, resistant varieties reached the wave crest earlier than the susceptible ones, itexplained that S. sclerotiorum was able to induce the production of chitinase. There was apositive correlation between rape resistance and its chitinase activity. Chitinase activityinduced by strong pathogenic strain NG4was higher than weak pathogenic strain WW2.Inhibition of chitinase to mycelial growth of S. sclerotiorum: chitinase crude enzymeextracted from infected rape leaves could inhibited mycelium growth of S. sclerotiorum invitro, however, S. sclerotiorum mycelial continued to growth in the control area. It showedthat chitinase had a certain antibacterial activity to S. sclerotiorum.