Effects of different rotation patterns on the occurrence of clubroot disease and diversity of rhizosphere microbes

Clubroot disease, caused by Plasmodiophora brassicae, is one of the most destructive soil-borne diseases in cruciferous crops worldwide. New strategies are urgently needed to control this disease, as no effective disease-resistant varieties or chemical control agents exist. Previously, we found that the incidence rate and disease index of clubroot in oilseed rape decreased by 50 and 40%, respectively, when oilseed rape was planted after soybean. In order to understand how different rotation patterns affect the occurrence of clubroot in oilseed rape, high-throughput sequencing was used to analyze the rhizosphere microbial community of oilseed rape planted after leguminous (soybean, clover), gramineous (rice, maize) and cruciferous (oilseed rape, Chinese cabbage) crops. Results showed that planting soybeans before oilseed rape significantly increased the population density of microbes that could inhibit P. brassicae (e.g., Sphingomonas, Bacillus, Streptomyces and Trichoderma). Conversely, consecutive cultivation of cruciferous crops significantly accumulated plant pathogens, including P. brassicae, Olpidium and Colletotrichum (P<0.05). These results will help to develop the most effective rotation pattern for reducing clubroot damage.