Illumina sequencing reveals a rhizosphere bacterial community associated with foxtail millet smut disease suppression

Smut disease is a severe limiting factor in foxtail millet production, caused by the Ustilago crameri fungus. The aim of this study is to characterize specific bacterial populations that might contribute to smut disease suppression. Rhizosphere bacterial community compositions of three foxtail millet cultivars differing in smut disease resistance were compared using high throughput Illumina sequencing. As a disease-resistant cultivar, Jigu20 showed the lowest disease incidence (0.7 %) after Ustilago crameri inoculation, compared with 14.8 % and 62.5 % for Jingu21 and Changnong35, respectively. Under the Ustilago crameri-inoculation condition, higher bacterial diversity was present in the rhizosphere of Jigu20 (I.Ji20) than in other two soil samples (I.Jin21 and I.Chang35). The same trend was observed in enzyme activities of phosphatase, catalase, and polyphenol oxidase. Compared to I.Jin21 and I.Chang35, I.Ji20 harbored higher abundance of Actinobacteria, while lower abundance of Bacteroidetes and Firmicutes. At the genus level, the hierarchical cluster of I.Ji20 was clearly separated from I.Jin21 and I.Chang35. Pearson's correlation analysis showed that the abundance of Bradyrhizobium and Streptomyces was negatively correlated with smut disease incidence (P < 0.05). Different smut resistant cultivars occupied different rhizosphere bacterial communities, and smut disease suppression might be correlated with high bacterial diversity.