Function Of Soybean Isoflavoes On Induced Resistance To Soybean Cyst Nematode

Soybean cyst nematode(SCN)is the most damaging pest of soybean,and caused seriously the yield loss in China.Soybean isoflavones are phytoalexin against plant diseases and nematodes.About six exogenous soy isoflavones were selected to identify the nematicide effect on SCN.Meanwhile,related isoflavones gene expression and content of related biosynthesis enzymes in soybean isoflavones synthetic metabolic pathways were tested,in order to clear the role of soy isoflavones under the rhizobium Sneb183(Sinorhizobium fredii)induced resistance to SCN.The results were as following.1.Bioactivity of six kinds of soybean isoflavones on SCN.Six exogenous soy isoflavones,including Daidzein,Daidzin,Genistein,Genistin,Glycitin and Glycitein,were selected the nematicidal activity on SCN by inhibiting rate of egg hatch-ability and second-stage juveniles(J2)activity.In addition,control effect of soybean seeds soaked with isoflavones were executed in the field.The results showed that the six isoflavones could effectively inhibit SCN.The 100 ?g/mL Genistein,among of them,showed the best inhibitory effect on the corrected mortality of J2 and the inhibition rate of egg hatching.The corrected mortality of J2 were respectively 45.46%and 56.86%,and the inhibition rate of egg hatching were respectively 43.48%and 48.48%when treated by Genistein for 24 h and 72 h,also the control effection of cysts in the field was 49.47%by 50 ?g/mL genistein treatment.Followed by Genistin and Daidzein significantly killed J2 and inhibited egg hatching,but the control effection were weaker than others in the soybean field.And then Glycitin and Glycitein had weaker toxicity on J2 than Genistin and Daidzein,while the inhibition efficiency of egg hatching was stronger than others.Furthermore,Daidzin showed weaker inhibition of J2 and egg hatching than other 5 species of soy isoflavones,but the control effection in the field showed the same as Genistein.2.Expression of soybean isoflavone relative genes under biological stress:The relative gene expression of three key enzyme genes,including genes of chalcone reductase(CHR),chalcone synthase(CHS)and chalcone isomerase(CHI),which related to isoflavones biosynthesis in soybean root,was determined by fluorescence quantitative PCR(Q-PCR).The results showed that gene relative expression quantity of CHR,CHS and CHI increased than CK,especiely in the process of soybean both induced by rhizobium Sneb183 and infected by SCN,3 genes expression were significantly higher than that of respectively infected with nematode alone and only inoculated Sneb183 at 7 h sample time.But,there was no significantly difference between SCN alone and Sneb183 alone.3.Key biosynthesis enzyme contents of soybean isoflavone under biological stress.Three key enzyme activity,including chalcone reductase(CHR),chalcone synthase(CHS)and chalcone isomerase(CHI),was detected by enzyme linked immunosorbent assay(ELISA).The results showed that the contents of CHR,CHS and CHI in the treated groups were more than CK.It was the most contents of CHR,CHS and CHI in the process of soybean both induced by rhizobium Sneb183 and infected by SCN among the three groups.Followed by that of SCN alone infection,the content of CHR,CHS and CHI was higher than that of inoculated Sneb183 alnoe at 8 h sample time.The results confirmed that the key enzymatic genes expression of soy isoflavones biosynthesis can be induced by Snebl83 and SCN jointly or separately.Genistein and other types of soybean isoflavones were confirmed against soybean cyst nematode,at the same time,the key biosynthesis enzyme of soybean isoflavones can be induced expression by rhizobium Sneb183 and SCN in the study.