二甲基二硫熏蒸对保护地连作土壤微生物群落的影响

随着保护地高附加值经济作物的连年栽培, 土传病害问题愈发突出, 熏蒸剂也因此得以更广泛的应用。但鉴于熏蒸剂的广谱性, 在杀死有害生物的同时, 不可避免地对非靶标生物产生一定的影响。为明确溴甲烷替代药剂二甲基二硫(dimethyl disulfide, 简称DMDS)熏蒸对土壤微生物群落的影响, 本研究在室内条件下采用BIOLOG 方法, 测定不同浓度DMDS 熏蒸对保护地连作土壤微生物群落的影响。研究结果表明: 不同浓度DMDS(170.00 mg·kg^-1、85.20 mg·kg^-1、42.50 mg·kg^-1、21.30 mg·kg^-1 和10.62 mg·kg^-1)熏蒸处理对镰孢菌属(Fusarium spp.)和疫霉菌属(Phytophthora spp.)的LC₅₀(抑制中浓度)分别为42.08 mg·kg^-1 和115.15 mg·kg^-1。DMDS 熏蒸后恢复培养0 d 取样, 温育120 h 时, 170.00 mg·kg^-1、42.50 mg·kg^-1 和10.62 mg·kg^-1 的DMDS 处理土壤的AWCD 值(平均每孔颜色变化率, average well-color development, AWCD)分别比空白对照升高8.46%、6.02%、19.31%, 表明DMDS 促进了土壤微生物的生长。恢复培养14 d 后, 各处理土壤微生物的AWCD 值恢复至对照水平。多样性指数分析显示, DMDS 熏蒸后恢复培养0 d 时, 土壤微生物群落的Shannon 指数、Simpson指数均高于空白对照, McIntosh 指数与对照无显著性差异; 恢复培养7 d 后, Shannon 指数与Simpson 指数恢复至对照水平。主成分分析结果显示, DMDS 熏蒸后恢复培养0 d 时, 各处理间微生物对碳源的利用方式差异显著, 恢复培养14 d 后, DMDS 对微生物碳源利用方式的影响逐渐减弱, 恢复至对照水平。结果表明, DMDS 熏蒸处理对土壤微生物的生长具有促进作用, 影响了微生物对碳源的利用方式, 但在恢复培养14 d 后, 被干扰的土壤微生物逐渐恢复至对照水平。DMDS 熏蒸处理在有效防控土传病原真菌的同时, 不会对土壤微生物群落产生明显的扰动影响, 对环境较安全。

Effects of dimethyl disulfide on microbial communities in protectorate soils under continuous cropping

Soil fumigants are widely used to protect agricultural and high-value cash crops from soil-borne diseases. As broad-spectrum agents, however, fumigants also have side effects on non-target organisms. Dimethyl disulfide (DMDS) is a new alternative to methyl bromide (MeBr) that reduces plant fungal pathogens and nematodes. DMDS is therefore recommended by the Methyl Bromide Technical Options Committee of the United Nations Environment Program (UNEP). This study was an attempt to identify the effects of DMDS on microbial communities in protectorate soils under continuous cropping. The efficacy of DMDS was evaluated by bio-assay in the laboratory. The efficacy of DMDS on the Fusarium spp. and Phytophthora spp. was observed after fumigations. The LC₅₀ of DMDS with different concentrations (170.00 mg·kg^-1, 85.20 mg·kg^-1, 42.50 mg·kg^-1, 21.30 mg·kg^-1 and 10.62 mg·kg^-1) was 42.08 mg·kg^-1 and 115.15 mg·kg^-1, respectively to Fusarium spp. and Phytophthora spp. Microbial community structures after DMDS fumigation were evaluated using BIOLOG Ecoplates under laboratory conditions. Compared with the untreated/control plants, the average well color development (AWCD) of the DMDS 10.62 mg·kg^-1, 42.50 mg·kg^-1 and 170.00 mg·kg^-1 respectively increased by 8.46%, 6.02% and 19.31%, 0 day after fumigation and 120 h after sample incubation. AWCD increased by 1.87%, 3.47% and 8.01%, respectively, 240 h after incubation; which indicated that DMDS promoted the growth of microbes. AWCD of treated samples were close to the control at 14 days after fumigation. The indices of Shannon and Simpson at 0 day after fumigation were higher than that of the control, recovering to the levels of the control 7 days after fumigation. Based on McIntosh index, there was no significant difference between the fumigation treatments and the control. Principal component analysis of substrate reaction reflected that the use of carbon sources by microbial community was obviously different in the treatments immediately after fumigation. It was, however, close to the control 14 days after fumigation. The study showed that DMDS fumigation promoted microbial activity, and affected the carbon sources consumption of microbe. However, effects became very weak and the indicators recovered to the levels of the control treatment at 14 days after fumigation. It indicated that DMDS fumigation not only effectively controlled soil-borne pathogen spread, but was also environmentally safe. The study laid the basis for a scientifically-guided use of fumigants.