Diversity Analysis Of AM Fungi In Continuous Cropping Soybean Rhizosphere Soil

Soybean is the fourth largest grain crop and an important oil crop in China.For a long time,domestic soybean acreage had been exhibited continuous cropping and the acreage had accounted for 20% in our country,which should be given an increasing attention..Affected by the market demand,the phenomenon about soybean continuous cropping was especially serious in Heilongjiang province,and the acreage had been up to 50% ~ 70% in recent years.Though some reports showed that Arbuscular mycorrhizal(AM)fungi could confer plant tolerance to biotic stress significantlly,whether the AM fungi can withstand the bad effect caused by continuous cropping had few report.Conbinated the traditional morphological method and nested PCR-DGG,the research about influence to the AM fungi flora structure from diverse varieties of soybean caused by the length of continuous cropping had bee performed in this paper,which provide the theory basis to study that AM fungi confer antagonism to soybean continuous cropping.1.The rate of AM fungi infecting into different soybean varieties in birth period had been determinated by dissociation alkali-acid fuchsin staining.Restult showed that the length of continuous cropping could change the rate.Meanwhile,different varieties and different periods in the same soybean variety could also affect AM fungi infection rate.2.The statistical AM fungi infection rate also revealed that the increasing length of continuous cropping could improve the rate.The rate from double continuous cropping was obviously higher than that from one year.In the same length of continuous cropping,the rate of AM fungi infecting to the seedlings of HN37 was highest,but in branch period,HN48 infected rate was highest.These results demonstrated different soybean varieties in various development stages changed AM fungi infection rate significantly.3.After several tests,the suitable DGGE condition for AM fungi had been ultimately determined.Electrophoreses were running for 9h at 130 V on a 8.0% acrylamide/bis gel with a 40–65% denaturant gradient.The purified PCR products were used for DGGE analysis.All DGGE analysis was run at a constant temperature of 60?.4.In this experiment,16 DGGE bands had been sequenced.The dominant AM fungi in the experimental filed colud ben divided into Funneliformis mosseae and Glomus,and some other unkown acaulospora.Phylogenetic analysis also showed that these unkown acaulospora had close relationship with the two main fungi.These result showed that the two genera AM fungi were dominant in the soybean rhizospheric soil environment in the filed,which also had the highest infection rate to soybean roots.5.In addition to AM fungi,Sarcosomataceae fungi(M15,homology with 91%)had also been identified,indicating that the non-specificity of the primers selected in this experiment.6.The length of continuous cropping,soybean variety and various development stages had some effects on the DGGE profile of AM fungi in the rhizosphere,which is consistent with the infection rate.In DGGE profile,the dominant population and the lowest dominant population had been changed,indicating that the length of continuous cropping had effects on the flora structure of AM fungi from different soybean varieties.