Effect Of Cropping Patterns And Nematicides On Yield And Communities Of Nematodes, Fungi, Bacterial In The Rhizosphere Of Sweet Potato

Potato rot nematode (Ditylenchus destructor) caused serious diseases, great losses in sweet potato, and destructed biotic communities diversity in rhizosphere soil. In this study, field experiment was conducted in Changli County, Hebei province during2009-2010, the treatments were:Al fallow-sweet potato; A2maize-fallow-sweet potato; A3maize-rye-sweet potato; A4soy bean-fallow-sweet potato; A5soy bean-rye-sweet potato; A6sweet potato. Potato rot nematode samples from6provinces in China, and11samples of Ditylenchus from other countries were collected to identify their classification with ITS,18S and RAPD. Pot experiment and contrast experiment were carried out to investigate the effect of different crop patterns and different nematicides on yield and the community structures of nematodes, bacterial and fungi in rhizosphere soil of sweet potato The main conclusions were as follows:1. Compare with continuous cropping, rotations significantly promote yields of sweet potato, decrease numbers of potato rot nematode, but different rotations had no significant difference on sweet potato yield and disease index (p<0.05). Rotations significantly improved the diversities of nematode, fungi and bacterial communities in sweet potato rhizosphere soil. A6was the best mode, rotations with rye in winter made nematode community structures more stable. A2and A3made the bacterial community structure stable, little vary with growth stages of sweet potato.2. Based on3kinds of gene fragments analysis, Ditylenchus dipsaci and D. Weischeri were in one cluster, while D. destructor, D. myceliophagus and D. africanus with round tail,6side glands, mycophagous were more similar, could be seperated from the traditional plant parasitic Ditylenchus into Safianema Sddiqi(1980) genus, the result proved the taxonomy of Safianema on molecular biology level.6samples from Inner Mongolia, Jilin, Henan, Shandong, Jiangsu, and Hebei in China were D. destructor.3. According to the result of contrast experiment, in fields, rotation got significant highest yields (p<0.05), and the number of potato rot nematode in September had significant correlation with sweet potato yield and desease index; while in pots, nematicides got significant highest yields (p<0.05), and the number of potato rot nematode in July had significant correlation with sweet potato yield; Rotation treatments in field and pot had no significant different effect on fungi and bacterial communities. In pot environment, the community structure of nematode, fungi and bacterial were more influenced by different growth stages of sweet potato.4.5nematicides, expect Paecilomyces lilacinus, could significantly increase yields of sweet potato, decrease the disease index and numbers of potato rot nematode, and significantly reduced the diversities of nematode, fungi and bacterial communities in sweet potato rhizosphere soil (p<0.05)5. Based on PCR-DGGE,9genus of nematodes were detected in rhizosphere soil of sweet potato b: Dorylaimus, Ditylenchus, Aphelenchoides, Cephalobus, Pratylenchus, Criconemella, Belonolaimus, Aphelenchus, Diplogasterida. The results of morphological identification were similar with DGGE.7fungi phylums were detected in the rhizosphere soil of sweet potato:Agaricomycotina、 Ascomycetes、 Chromalveolata、Dothideomycetes、Eurotiomycetes、Sordariomycetes and Zygomycetes.7bacterial phylums were detected:Bacteroidetes, Proteobacteria, Acidobacteria, Actinobacteria, Gemmatimonadetes, Planctomycetes and Chloroflexi.