The Effect Of Potato Continuous Cropping And Intercropping On Genetic Diversity Of Soil Microorganism In Loess Plateau Of Ningxia

Potato was very important high-yield crops in Loess Plateau of Ningxia, which acted an important role in agriculture produce of whole region. Because of the limitation of land resources, the phenomenon of potato continuous cropping was widespread. The genetic diversity of soil microorganism was studied by using BOXAIR-PCR,16S rDNA and T-RFLP technique. which provided the theoretical basis to study the causes of the potato continuous cropping obstacle. The results of the study were as follows:(1) The results showed that total91strains were isolated from8soil samples of potato continuous cropping. The variance range of genetic similarity about91strains was0.531-0.939.There were distribution differences of bacterial communities in same continuous cropping year but different growth stages, as well as in the rhizosphere soil of potato period, and as the year increased, the genetic diversity of culturable bacteria declined, which indicated that a highly diversity was in91strains.41representative strains were selected by restriction endonuclease map, which were classified23species in12genera of bacteria, and the strains belonged to genus of bacillus was the predominant one among them. With the increasing of continuous cropping years, the bacteria community structure was changed, and the specific genera of bacteria were found also.23bacteria species were distributed in6groups of phylogenetics.(2) With the increasing of continuous cropping years, The genetic diversity of soil bacteria declined, while the genetic diversity of fungus increased. The genetic diversity level of soil microorganism has nothing to do with the growth period, moreover, the non-rhizosphere soil bacterial and fungal diversity level was higher than that of rhizosphere soil.(3) The analysis of continuous cropping soil bacteria flora revealed that, the proportion of each soil bacteria class changed greatly, the proportion of Bacilli and Sphingobacterium declined as the cropping year increased while the proportion of β-proteobacterium class increased. Potentially pathogenic bacteria, such as Ralstonia was appeared in the soil of continuous cropping10years.(4) The analysis of continuous cropping soil fungal flora revealed that, the proportion of Dothideomycetes capnodiales was the largest among all orders. Dothideales and Trichosporonales were special orders in rhizosphere soil, while Xylariales and Dacrymycetales were special orders in non-rhizosphere soil.(5) Intercropping cultivation model changed the genetic diversity of soil bacteria and fungus, the potato/horsebean intercropping was a better improvement for continuous cropping soil than potato/corn or potato/buckwheat, and the longer continuous cropping years, the better improvement effects.