Soil fumigation based on ammonium bicarbonate suppressed cucumber Fusarium wilt disease associated with soil microflora alteration. uncultured bacterium

Cucumber yield and quality are seriously compromised by Fusarium wilt in the southern China. Soil bacteria and fungi are, however, also critical to the ecological functioning of soils and plant health and were thus the study subject here. Using Miseq pyrosequencing, the entire soil bacterial and fungal communities of a field where cucumber had been consecutively cultured for five years. Bacterial and fungal richness, community composition, and relative taxon abundances in soil were compared among the different treatments. 7,879 bacterial OTUs at 97% 16S sequence identity were found among 655,756 sequence reads while 1896 fungal operational taxonomic units at 97% ITS sequence identity were found among 295,129 sequence reads derived from 12 separate soil samples. Compared to the CK-OF-treated soil samples, LAB-OF-treated soil revealed higher abundances of Gemmatimonadetes, Verrucomicrobia, Chytridiomycota and Zygomycota while Proteobacteria, Acidobacteria, Ascomycota, Basidiomycota and Glomeromycota were found in lower abundance. Correlation analysis showed that the abundance of Ascomycota and Basidiomycota were lower in LAB-OF-treated soil, and they were positively correlated with disease suppression while Verrucomicrobia was higher and it was negatively correlated with disease suppression while positively correlated with the soil nitrate content. In sum, Fusarium wilt disease after long term continuous cropping can be attributed to the alteration of the soil microbial community membership, the reduction of the beneficial microbes and the accumulation of the fungal pathogen.