Effect of rotation on nematode community diversity in rhizosphere soils and yield of sweet potato

Sweet potato rot nematode (Ditylenchus destructor) is a severe disease that can cause significant loss of sweet potato yield and that can destroy biotic community diversity in rhizosphere soils. In this study, nematode community structure in rhizosphere soils under sweet potato were investigated to verify the impact of rotation cropping patterns on rot nematode disease and the feasibility of denatured gradient gel electrophoresis (DGGE) in soil nematode research. The experiment was conducted on a long-term continuous sweet potato field in Lulong County, Hebei Province in 2014 to (→) 2015, where sweet potato rot nematode disease was seriously epidemic. The cropping patterns were included A1 (fallow→sweet potato), A2 (maize-fallow→sweet potato) A3 (maize-rye→sweet potato), A4 (bean-fallow→sweet potato), A5 (bean-rye→sweet potato) and CK (continuous sweet potato cropping). The nematodes were separately extracted from sweet potato rhizosphere soil in May, July and September in 2015, and the ITS genes analyzed using PCR-DGGE. The results showed that compared with continuous cropping, crop rotation significantly increased the diversity of nematode community, and decreased the population of sweet potato rot nematode in rhizosphere soil (P < 0.05). Community structure of nematodes in rhizosphere soil under sweet potato was stabilized by winter rotation with rye (A3 and A5). Based on PCR-DGGE, 9 genera of nematodes were detected in the rhizosphere soil of sweet potato-Ditylenchus, Dorylaimus, Aphelenchoides, Cephalobus, Pratylenchus, Criconemella, Belonolaimus, Aphelenchus, and Diplogasterida. While Ditylenchus was the dominant genus in all the cropping patterns, Dorylaimus, Aphelenchoides and Cephalobus were the main genera. Crop rotation increased sweet potato yield by 42.08%-55.83% and decreased disease index by 22.72%-30.79%. However, different crop rotations had no significant difference on sweet potato yield and disease index. The population of Ditylenchus destructor was significantly related with sweet potato yield and disease index at harvest time (P < 0.05). Therefore, crop rotation significantly increased the diversity of nematode communities in sweet potato rhizosphere soils and sweet potato yield. And DGGE was proved to be a useful tool to detect soil nematode community. For the economic and ecological effects, bean-rye→sweet potato was the best rotation pattern for the study area.