旱区盐生植物根际促生菌的分离鉴定及其干旱、盐胁迫下促生特性

【目的】从在干旱、高盐碱生境下生长的盐生杂类草根际土壤中分离具有耐盐和促生性能的根际微生物,并研究其促生特性,为改良旱区土壤盐碱化提供优质菌种资源和理论基础。【方法】通过选择培养基筛选具有耐盐、解磷和解钾能力的菌株,再检测菌株产生长激素(indole-3-acetic acid,IAA)、产1-氨基环丙烷-1-羧酸(1-aminocyclopropane-1-carboxylate,ACC)脱氨酶、产铁载体以及产胞外多糖的能力,选择性状优良者通过拮抗实验组建复合菌剂。并采用菌液侵染萝卜和玉米种子验证菌株对在盐胁迫下种子发芽率和植株在干旱与盐双重胁迫下生长的影响。最后通过16S rRNA基因测序进行分子生物学鉴定。【结果】得到3株具有良好耐盐促生能力的根际微生物yl923、hs032和hy127,菌株yl923兼具解磷(46.29 mg/L)、解钾(58.07 mg/L)、产IAA(29.23 mg/L)、产ACC脱氨酶(13.83 U/mg)和产铁载体(SU=0.43)能力,菌株hs032具有最强产IAA(61.18mg/L)和产铁载体(SU=0.23)能力,菌株hy127具有最强产ACC脱氨酶(15.29U/mg)能力。经16SrRNA基因序列分析后分别将yl923和hs032鉴定为枯草芽孢杆菌(Bacillus subtilis),hy127鉴定为巨大普里斯特氏菌(Priestia megaterium)。3株菌互不拮抗可组建复合菌剂,2%混合菌液可提高种子在盐胁迫下种子发芽率(77%),对干旱和盐胁迫下玉米的根长、株高、干重和叶绿素也都有显著的提高(P<0.05),并且可以显著地降低玉米体内丙二醛(malondialdehyde,MDA)含量(60%)。【结论】菌株yl923、hs032和hy127具有优秀的耐盐促生性能,组合成的混合菌剂能在干旱和盐胁迫下促进植物的生长,具有改良旱区盐渍化土壤的潜力。

Isolation and identification of growth-promoting bacteria in halophyte rhizosphere in arid region and their growth- promoting characteristics under drought and salt stresses

Objective] We isolated and screened microbes with growth-promoting function and salt tolerance from the rhizosphere soil of halophytes in dry and saline habitats and studied their growth-promoting ability, hoping to provide high-quality bacterial resources and a reference for alleviating soil salinization in arid areas. Methods] Strains with salt tolerance and phosphate-solubilizing and potassium-releasing abilities were screened with selective media. Then, the ability of the strains to produce indole-3-acetic acid (IAA), 1-aminocyclopropane-1-carboxylate (ACC) deaminase, siderophore, and exopolysaccharide was tested. Through antagonism test, strains with excellent functions and no antagonism to each other were selected to prepare the compound bacterial mixture. The suspension of each of the strains and that of the mixture of strains without antagonism to each other were respectively used to infect seeds of radish and maize, and the influence on seed germination rate under salt stress and plant growth under both drought and salt stresses was observed. Finally, 16S rRNA gene sequencing was performed to identify the strains. Results] Strains yl923, hs032, and hy127 with salt tolerance and growth-promoting ability were screened out. yl923 can solubilize phosphate (46.29 mg/L), help release potassium (58.07 mg/L), and produce IAA (29.23 mg/L), ACC deaminase (13.83 U/mg), and siderophores (SU=0.43). hs032 was outstanding in producing IAA (61.18 mg/L) and siderophore (SU=0.23) and hy127 excelled in producing ACC deaminase (15.29 U/mg). Through 16S rRNA gene sequencing, yl923 and hs032 were identified as Bacillus subtilis and hy127 was determined to be Priestia megaterium. The three showed no antagonism to each other and thus they can be used together as compound bacterial mixture. The 2% mixture suspension can improve the seed germination rate (77%) under salt stress. Moreover, it can increase the root length, plant height, dry weight, and chlorophyll production (P<0.05), and significantly reduce the malondialdehyde (MDA) content (60%) of maize under drought and salt stresses. Conclusion] Strains yl923, hs032 and hy127 show excellent salt tolerance and growth-promoting function. The compound mixture prepared with the three can remarkably promote plant growth under drought and salt stresses and those strains have the potential to improve salinized soil in arid regions.