Bacterial community structure and functional potential of rhizosphere soils as influenced by nitrogen addition and bacterial wilt disease under continuous sesame cropping

Effects of nitrogen addition and bacterial wilt disease on bacterial diversity, community structure and functional potential in rhizosphere soil under continuous sesame cropping were investigated by a field experiment and Illumina sequencing using two cultivars (Jinhuangma and Zhongzhi No.35) under two nitrogen levels (0-N0 and 105-N1 kg N ha-1) with rhizosphere soil (RS) samples collected from healthy (not infected with bacterial wilt disease) and diseased (infected with bacterial wilt disease) plants. The bacterial diversity was not affected by nitrogen addition and bacterial wilt disease (p > .05).The relative abundance of Ralstonia solanacearum was 0.15 and 0.11 percentage points higher in the Diseased than in the Healthy RS samples for the two cultivars(p < .05). N1 had a decrease of 0.708 percentage points in the relative abundance of genus Roseiflexus as compared to N0 in Jinhuangma (p = .031). Additionally, compared to N1, N0 of Zhongzhi No.35 had an increase of 0.593-2.064 percentage points in the relative abundance of five genera, such as uncultured-f-Acidobacteriaceae_Subgroup_1, Candidatus_Solibacter, Bryobacter, Rhizomicrobium and Subgroup_2_norank (p < .05). Furthermore, the Diseased RS samples of Jinhuangma were 0.655 and 0.569 percentage points higher than the Healthy RS samples in the relative abundance of Phenylobacterium (p = .031) and Pseudonocardia (p = .013). The diseased samples of Zhongzhi No.35 were 1.007-1.867 percentage points higher than healthy samples in the relative abundance of Burkholderia (p = .045), Massilia (p = .031), Phenylobacterium (p = .021) and Novosphingobium (p = .005), but it was just the opposite for the other six genera (p < .05). The function potential of bacterial community varied significantly between Diseased and Healthy RS samples (p < .05). Overall, nitrogen and bacterial wilt disease had a significant impact on the structure of bacterial communities in rhizosphere soil, and signal transduction and translation could play an important role in preserving plant health.