| Long-duration of continuous potato cropping has been one of the severeproblems that declines the popato tuber yield and induces soil-borne diseases in theirrigated areas by the Yellow River in middle parts of Gansu Province. Aiming at thisproblem, a field experiment was carried out in Jingtai county of Gansu Province in2011to study the effects of continuous potato cropping on bacterial and fungalmicrobial communities of rhizosphere soils by means of PCR-DGGE technique, toprovide more understanding to the machanisms of potato cropping obstacles. Inexperimental site, the rotation cropping field is CK（the year of continuous potatocropping is zero years, L0）, the treatments were the years for continuous potatocropping, from one year to six years （L1-L6）.The main results were as follows:1． Effects of continuous potato cropping on genetic diversity of bacterium inrhizosphereContinuous cropping significantly affected the bacterial genetic diversity. Theresults for DGGE were as follows, continuous cropping potato made bacterialoperational taxonomic unit （OTU） decreased significantly, while Richness (R)reduced. The degree of reduction varied with the different growth period, and the soilwas mainly affected before planting. Before sowing, seedling, tuber forming and tuberexpansion period, compared with L0, L1-L6rhizosphere bacteria richness decreasedby24.2%-34.5%，0-16.7%，21.6%-31.1%and17.8%-26.2%.In the DGGE profiles, the numbers of visible bands were the most in L0.Therewere29,36,37and42OTU before sowing, seedling, tuber forming and tuberexpansion period, after six years of continuous cropping OTU number reduced to21,32,26and31, decreased by27.6%,11.1%,29.3%and26.2%, compared with thecontrolled L0.Bacterial diversity index of Potato rhizosphere decreased with the increase of thecontinuous potato cropping.Bacterial diversity index in different growing stages hadthe different changing trends. Compared with L0, L1-L6rhizosphere bacteria diversity index （H） decreased by12.5%、11.5%、20.8%、8.1%and7.8%, beforesowing, seedling, tuber forming, tuber expansion period and mature period, whichshowed that the structure of bacteria in potato rhizosphere tends to single aftercontinuous cropping.The rhizosphere bacteria diversity index showed obvious parabola in thecontrolled L0, and reached the maximum in tuber expansion period. Continuouscropping changed the diversity development trend of the rhizosphere bacteria..The sequencing results of the bacterial DGGE bands showed that aftercontinuous cropping proteobacteria took the majority in potatoes rhizosphere bacteria,while acidobacteria, actinobacteria and gemmatimonadetes were very few.2. Effects of continuous potato cropping on genetic diversity of fungi in rhizosphereContinuous cropping significantly affected the fungal genetic diversity. Theresults for DGGE were as follows, continuous cropping potato made fungaloperational taxonomic unit（OTU）decreased significantly, and Richness reduced. Inmature period, the controlled L0has18OTU, after continuous cropping, L1-L6OTUnumbers reduced to18,14,13,14and13, compared L0which was reduced by0,22.2%,27.8%,22.2%and27.8%respectively.After continuous cropping, the trend of fungal diversity index (H)is differentinmature period. Taking the tuber formation period as a dividing line, H first increasedand then decreased in L0and L1, and went back to the higher level, while H in L2-L6decreased with the advance of the growth period. Compared with the controlled L0,L1-L6fungal diversity index （H） was reduced by2.8%,13.0%,12.2%,15.3%and15.3%respectively.The sequencing results of the bacterial DGGE bands showed after continuouspotato cropping, ascomycota took the majority in rhizosphere fungal andBasidiomycota was few... |
PDF Full Text Request