Changes in the soil microbial community after reductive soil disinfestation and cucumber seedling cultivation

Reductive soil disinfestation (RSD) has been proven to be an effective and environmentally friendly way to control many soilborne pathogens and diseases. In this study, the RSDs using ethanol (Et-RSD) and alfalfa (Al-RSD) as organic carbons were performed in a Rhizoctonia solani-infected soil, and the dissimilarities of microbial communities during the RSDs and after planting two seasons of cucumber seedlings in the RSDs-treated soil were respectively investigated by MiSeq pyrosequencing. The results showed that, as for bacteria, Coprococcus, Flavisolibacter, Rhodanobacter, Symbiobacterium, and UC-Ruminococcaceae became the dominant bacterial genera at the end of Al-RSD. In contrast, Et-RSD soil involved more bacteria belonging to Firmicutes, such as Sedimentibacter, UC-Gracilibacteraceae, and Desulfosporosinus. For fungi, Chaetomium significantly increased at the end of RSDs, while Rhizoctonia and Aspergillus significantly decreased. After planting two seasons of cucumber seedlings, those bacteria belonging to Firmicutes significantly decreased, but Lysobacter and Rhodanobacter belonging to the phylum Proteobacteria as well as UC-Sordariales and Humicola belonging to Ascomycota alternatively increased in Al- and Et-RSD-treated soils. Besides, some nitrification, denitrification, and nitrogen fixation genes were apparently increased in the RSD-treated soils, but the effect was more profound in Al-RSD than Et-RSD. Overall, Et-RSD could induced more antagonists belonging to Firmicutes under anaerobic condition, whereas Al-RSD could continuously stimulate some functional microorganisms (Lysobacter and Rhodanobacter) and further improve nitrogen transformation activities in the soil at the coming cropping season.