Institute of Agriclutural Engineering, The Volcani Center, Bet Dagan, Israel.
Phytopathology. 2010 Apr;100(4):367-75. doi: 10.1094/PHYTO-100-4-0367.
Preplant soil fumigation with metam sodium is used worldwide to control soilborne diseases. The development of accelerated degradation of pesticides in soil, including metam sodium, results in reduced pesticide efficacy. Therefore, we studied microbial involvement in accelerated degradation of methyl isothiocyanate (MITC) following repeated soil applications of the parent compound, metam sodium. MITC degradation was reduced in soil with a history of metam sodium applications following sterilization, indicating the key role of microorganisms in accelerated degradation. Accelerated degradation of MITC was induced by inoculation of soil with no previous application of metam sodium with soil with a history of metam sodium applications. We developed a method to extract the active microbial fraction responsible for MITC degradation from soil with a history of metam sodium applications. This concentrated soil extract induced accelerated degradation of MITC when added to two different soils with no previous application of metam sodium. An extensive shift in total bacterial community composition in concentrated soil extracts occurred after a single metam sodium application. Two Oxalobacteraceae strains, MDB3 and MDB10, isolated from Rehovot soil following triple application of metam sodium rapidly degraded MITC in soil with no previous application of metam sodium. Polymerase chain reaction-denaturing gradient gel electrophoresis analysis of bacterial community composition showed relative enrichment of MDB3 following metam sodium application, suggesting its potential in situ involvement in accelerated degradation development in Rehovot soil. Responses of resident Oxalobacteraceae community members to metam sodium applications differed between Rehovot and En Tamar soils. Isolate MDB10 did not induce accelerated degradation of MITC in En Tamar soil and, with the slow dissipation of MITC, soil suppressiveness of accelerated degradation is suggested. The isolation and identification of MITC-degrading bacteria might be helpful in developing tools for managing accelerated degradation.
土壤预植前用甲硫威进行熏蒸处理，被全世界用于防治土传病害。包括甲硫威在内的农药在土壤中的加速降解导致药效降低。因此，我们研究了在重复使用甲硫威处理土壤后，土壤中微生物对甲基异硫氰酸酯（MITC）加速降解的作用。土壤经灭菌处理后，其 MITC 降解率在经历过甲硫威处理的土壤中降低，这表明微生物在加速降解中起着关键作用。用未使用过甲硫威的土壤接种有甲硫威处理史的土壤，可诱导 MITC 加速降解。我们开发了一种从有甲硫威处理史的土壤中提取负责 MITC 降解的活性微生物部分的方法。这种浓缩的土壤提取物在添加到两个以前未使用过甲硫威的不同土壤中时，可诱导 MITC 加速降解。在单一甲硫威处理后，来自雷霍沃特土壤的 Oxalobacteraceae 菌株 MDB3 和 MDB10 的浓缩土壤提取物中的总细菌群落组成发生了广泛的变化。这两种 Oxalobacteraceae 菌株在没有以前应用过甲硫威的土壤中迅速降解 MITC。对土壤细菌群落组成的聚合酶链反应-变性梯度凝胶电泳分析表明，MDB3 在甲硫威处理后相对富集，这表明它在雷霍沃特土壤中的原位参与了加速降解的发展。驻留 Oxalobacteraceae 群落成员对甲硫威处理的反应在雷霍沃特和恩塔马尔土壤之间存在差异。分离株 MDB10 不会在恩塔马尔土壤中诱导 MITC 的加速降解，并且由于 MITC 缓慢降解，表明土壤具有抑制加速降解的能力。降解 MITC 的细菌的分离和鉴定可能有助于开发管理加速降解的工具。
