Effects of Biochar Application on Rhizosphere Microbial Community and Occurrence of Tobacco Bacterial Wilt

to investigate the effects of different application rate of biochar on rhizosphere microbial community and occurrence of tobacco bacterial wilt, field experiment was performed with randomized block design in the bacterial wilt disease prone plots. Based on conventional fertilization, different doses of biochar were applied ranging 750-7500 kg/hm², tobacco rhizosphere soil samples were collected at rosette and topping stage, and the effect of biochar on composition of the rhizosphere microbial communities was analyzed by using lllumina high-throughput sequencing technology. The results showed that in the the treatment of 7500 kg/hm², the disease index against tobacco bacterial wilt decreased 53.66%, while the treatment of 4500 kg/hm² obtained the best effect on the increase of rhizosphere soil pH, nitrate nitrogen and available phosphorus content at topping stage. The treatment of 7500 kg/hm² had the best effect on the increase of soil organic matter and available potassium content. The diversity of rhizosphere microbial in the treatment of 7500 kg/ hm² was lower than the other treatments at rosette stage, and Bacteroidetes was significantly enriched in rhizosphere soil at topping stage in the treatment of 7500 kg/hm². Furthermore, the treatment of 7500 kg/hm² could enrich Pirellula, Sphingopyxis, Quadrisphaera in rhizosphere soil at topping stage. At the level of fungal genera, Cryptococcus and Venturia were enriched in the rhizosphere soil of tobacco plants at rosette stage in the treatment of 3000 kg/hm². RDA results indicated that available potassium was the key promotion factor on the change of rhizosphere microbial community. In conclusion, the biochar application of 3000-7500 kg/hm² could change the rhizosphere microbial communities and might have potential application in the control of tobacco bacterial wilt.