Responses of Bacterial and Fungal Community Structure to Different Rates of 1,3-Dichloropropene Fumigation

Abstract

1,3-Dichloropropene (1,3-D) is a well-known nematicidal soil fumigant on many crop species. Currently, little is known about its impact on soil microbial communities using culture-free methods. In this study, we investigated changes in soil bacterial and fungal diversity and composition at two depths (30.5 and 61 cm) in response to management practices of applying 1,3-D at four different rates (103, 122, 140, and 187 liters/ha) relative to an untreated control in potato production fields using 16S rRNA and internal transcribed spacer (ITS) amplicon sequencing. A total of 12,783 operational taxonomic units (OTUs) for 16S and 1,706 OTUs for ITS were obtained. Sequencing revealed that Proteobacteria, Firmicutes, Actinobacteria, and Ascomycota were dominant phyla in soils. Comparing alpha diversity of microbial communities at the different chemical rates with untreated plots showed that bacterial communities in plots treated with 1,3-D fumigation at 140 liters/ha were richer, which was supported by higher richness indices. Other diversity indices and overall soil microbial community structure were not significantly influenced by any rates of 1,3-D fumigation, although higher bacterial and fungal richness and diversity were observed in posttreatment soils and/or at 30.5 cm. Of the identified microbial families, the differential abundance of 45 bacterial and 24 fungal families was affected by sample depth, 1,3-D rate, or the interaction of sample depth and 1,3-D. The bacterial family Enterobacteriaceae, which includes species that specialize in decay of complex carbohydrates, increased in abundance post-1,3-D fumigation, and the fungal family Ophiocordycipitaceae, which includes nematode and insect pathogens, decreased, suggesting that the nematode and soil insect death caused by fumigation may selectively impact specific fungal and bacterial families.