Resistance Related Enzymes Activity And Genes Expression Analysis Of Mung Bean Response To Cercospora Canescens Infection

Mung bean Cercospora leaf spot,caused by the fungus Cercospora canescens,is one of the devastating diseases on mung bean productions.However information about the mechanism of mung bean resistance against Cercospora canescens was limited.Therefore,in current study,we systematically studies the sporulation conditions,conidial germination conditions and inoculation methods of C.canescens.Subsequently,the evaluation of mung bean accessions resistance to C.canescens,defense related enzymes and genes response to C.canescens infection were also conducted for revealing the resistance mechanism.These results might be lay a foundation for further studies on C.Canescens and mung bean interaction,and the use of resistant varieties for disease prevention.The results of current study are as follows:1.The conditions of sporulation and conidial germination of C.Canescens were uncovered.Among the nine selected culture mediums,the sorghum grain medium was best for C.canescens sporulation.In the suitable condition of 25? with 12 h photoperiod,the C.Canescens will be sporulation within 10 days and produce 9×105 per milliliter of conidia after 14 days of incubation.The optimum condition for conidia germination was 25?,pH6~7 and complete darkness.Under this condition,the conidia can germinate after 3 h incubation and the germination rate reach to 88% after 24 h.The optimum carbon and nitrogen sources for conidia germination were sucrose and peptone,in which the germination rate were 87% and 86.3%,respectively.However,the germination rate of conidia with carbon and nitrogen source were not significant different compared with water,indicating that the carbon or nitrogen source was not necessary for conidia germination.2.The inoculation methods including inoculum,inoculation modes,incubation temperature and moisturizing time were conducted.Results showed that inoculation of mycelial block with puncture and spray conidia suspension with slight injury were suitable for studying the interaction between mung bean and C.canescens.In view of the convenience,inoculation of puncture with mycelial block was used in the subsequent experiments.The optimum condition for inoculation of mycelial block was keep moisture 24 h at 25?.Disease resistance of 18 mung bean varieties were identified by inoculation with mycelial block.Among these cultivars,there was 1 resistant cultivar,11 medium resistant varieties,4 medium susceptible varieties and 2 high susceptible cultivars.3.The activities of CAT,SOD,APX and POD in leaves of different resistant cultivars were studied.The CAT activity of the cultivars after inoculation was increased rapidly and maintained at a high level in the resistance cultivar.However,there was no significant difference in CAT activity in susceptible cultivar between different treatments.Additionally,the activity of SOD in resistant and susceptible cultivars increased rapidly and then decreased,but the resistant varieties reached the peak at the first day after inoculation.While the susceptible one reached the peak at 3 d after inoculation.The APX activity reached the peak at 1 d after inoculation with twice as high as that of the control,followed by a high level of activity.The activity of POD was significantly higher than that of the control.The POD activity of the cultivars was significantly higher than that of the control present as bimodal curve.While in susceptible cultivar,POD activity reached the maximum at 6 d after inoculation,but the increased extent of POD activity in susceptible cultivars was significantly higher than that in resistant one.The results showed that the overall trend of SOD,CAT,APX and POD in resistant cultivar were that shorter response time and higher response intensity against to the pathogen infection.These phenomenon might be the main reason for disease resistance.4.The relative expression of phenylalanine ammonia lysozyme(PAL),?-1,3-glucanase(GLU)and chitinase(CHI)gene in leaves after inoculation.The results showed that PAL,GLU and CHI genes were activated earlier and significantly up-regulated in resistant cultivar compared with susceptible cultivar.Pathogen infection stimulates the expression of these three genes that encode these disease-resistant proteins,and the coding products participate in the defense of mung bean infection against Cercospora leaf spot.