本研究从盐碱区域植物根际土壤中筛选到1株具有较高ACC脱氨酶活性[405.17 nmol/(g?h)]的耐盐促生菌Agrobacterium sp.DF-2.除ACC脱氨酶活性外,菌株还具有降解不溶磷活性,产生植物生长激素IAA,产胞外多糖等特性.此外,菌株可耐受最高8%NaCl浓度胁迫,证明其可应用到盐碱土壤中.通过盆栽试验研究了在75 mmol/L NaCl盐胁迫下接种DF-2对黄瓜幼苗的生长的影响以及作用机理.结果表明,与盐胁迫处理相比,接种DF-2处理幼苗株高、根长、生物量积累以及叶绿素含量分别显著增加15.08%、34.35%、13.10%和22.58%.同时,DF-2也增强宿主植物对K+的吸收,提高抗氧化酶活性和脯氨酸含量;降低对Na+的吸收和丙二醛含量.菌株DF-2主要通过高效的ACC脱氨酶活性,调控K+/Na+值,增强细胞清除活性氧能力和渗透调节能力等途径增强黄瓜幼苗的耐盐性.因此,耐盐促生菌Agrobacterium sp.DF-2具有作为生物肥料用于盐渍土的潜力.%An Agrobacterium sp.DF-2 with high 1-aminocyclopropane-1-carboxylate (ACC) deaminase activity was isolated from the rhizosphere of saline soil. Apart from producing ACC deaminase, the strain exhibited the plant growth-pro-moting traits of phosphorus-solubilizing activity and yielded IAA and exopolysaccharide. It could tolerate up to 8% NaCl concentration ( w/v) stress, indicating its potential for applications to saline soil. The effects of DF-2 inoculation on the growth and physiological responses of cucumber seedlings under salt stress and the mechanism were investigated by pot ex-periment. Compared to control plants under salt stress, inoculation with DF-2 significantly increased shoot, root and plant biomass and chlorophyll content by 15. 08%, 34. 35%, 13. 10% and 22. 58%, respectively. Moreover, DF-2 boosted the uptake of K+, antioxidant enzyme activi-ty and proline content, and reduced the uptake of Na+ and malondialdehyde content in the host plant. In conclusion, DF-2 enhanced cucumber seedlings salt tolerance through superior ACC deaminase activity, regulation of K+/Na+ra-tio, enhancement of ROS scavenging capacity and an os-motic adjustment ability of cucumber cells. The halotolerant Agrobacterium sp.DF-2 offers great potential for the use as a bi-ological fertilizer in saline soil agriculture to advance sustainable development.
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