The Mechanism Of Soybean PI 437654 In Response To Infection Of Heterodera Glycines RACE 3 And RACE 4

Soybean cyst nematode(Heterodera glycines,SCN)disease is one of the world's most devastating diseases in soybean production.It has the characteristics of wide distribution,heavy damage,and difficulty to control,which seriously threatens the safety of soybean production.Breeding new cultivars of resistant soybean is the most effective measure for the control of SCN.To study the mechanism of soybean response to SCN is the founder of breeding resistant soybean.It has great significance for breeding resistant cultivars to control SCN environmentally friendly and sustainablely.Soybean PI 437654 is a good resistant source which has a broad spectrum to all races and variants of SCN,but its mechanism in response to SCN is unknown.In this study,soybean PI 437654 was used as the object.After inoculation of SCN RACE 3 and RACE 4 at 1 d,4 d,8 d,12 d and 18 d,the developmental processes,feeding site structure and key defense related enzyme activities were used to analyze the histopathological and physiological-biochemical mechanisms;comparative transcriptomics was used to screen for differentially expressed genes to analyze the function of key resistance related gene preliminary.The main findings are as follows:1.There are significant differences in the developmental process of PI 437654 in response to different races of SCN.The number of SCN in roots was significantly lower and the developmental speed was significantly slower than that of the susceptible control at 1 dpi,4 dpi,8 dpi,12 dpi and 18 dpi.RACE 3 had the properties of significantly higher number and faster development process than RACE 3,however RACE 4 played a role in greater toxicity than RACE 3 during H.glycines RACE 3 and RACE 4 infection respectively.2.The paraffin sections of syncytium from soybean root after inoculation with different races and uninoculated control showed that soybean root column increased with time in uninoculated control.RACE 3 could be quickly colonized and formed hypersensitive response in the vascular bundle of PI 437654.It has caused damage to the structure of the column at the middle phase of infection,but then the syncytium degraded rapidly and its area decreased;RACE 4 invaded in the vascular bundle after moved around the cortex and the syncytium increased gradually.3.The activities of SOD,POD,PAL and PPO during H.glycines RACE 3 and RACE 4 infection in soybean PI 437654 were determined.The results showed that the activities of four main defense enzymes were higher compared to the uninoculated control.The activities of POD,PAL and PPO enzymes were all significantly higher than the control at 1 dpi,and the activity of SOD was higher than the control at 4 dpi and 8 dpi.There are significant differences between the activities of these four enzymes at 18 dpi and which infected by RACE 3 in PI 437654 roots were higher than RACE 4.4.The transcriptome sequencing results showed that there are differentially expressed genes(DEGs)after PI 437654 infected with H.glycines RACE 3 and RACE 4 respectively at 5 different time(1 d,4 d,8 d,12 d,18 d).The most DEGs were 1290,1201 and 791 respectively at 1 dpi,4 dpi and 8 dpi.GO functional annotation showed that these DEGs were mainly involved in oxidation-reduction and catalytic activity.The common DEGs were significantly reduced to 75 at 12 dpi compared to 8 dpi.These DEGs were mainly annotated as transport,localization,cell periphery expansion and changes of plasma membrane.62 genes were differentially expressed at 18 dpi.These genes were mainly enriched in the oxidation-reduction and catalysis process,in addition to changes of cell wall and extracellular domain,metal ion binding and cation binding process.5.Four reported SCN resistance genes(Glyma18g02580,GmSNAP18,Glyma18g02610,GmSHMT)and 75 syncytium-associated genes were selected from DEGs.The expression level of the three genes during H.glycines RACE 3 and RACE 4 infection in soybean PI 437654 showed that they played a slightly different role at the same period.All the three genes were highly expressed at 8 dpi,12 dpi and 18 dpi of RACE 3 and the expression level were higher at 1 dpi and 4 dpi of RACE 4.At the same time,RT-qPCR was performed to validate the results of four reported genes of syncytium Glyma13g38040,Glyma17g13550,Glyma15g18210 and Glyma05g17470.The results showed that there were differences in the expression levels of the four genes infected by RACE 3 and RACE 4 in PI 437654 roots.The expression levels of the 4 genes were higher at 8 dpi and 12 dpi of RACE 3;while the genes Glyma13g38040 and Glyma17g13550 were highly expressed at 1 dpi of RACE 4,and the genes Glyma15g18210 and Glyma05g17470 reached the highest expression levels at 12 dpi and 18 dpi of RACE 4.