耐盐促生芽孢杆菌的筛选及其对盐胁迫下燕麦生长的影响

从河北省秦皇岛滨海盐生植物根际土壤分离筛选耐盐促生芽孢杆菌,研究其在盐胁迫条件下对燕麦生长的促生效果,以期为研发耐盐促生菌剂和菌肥提供菌种资源。采用pH值9.0和NaCl质量分数分别为5%、10%、15%的LB培养基筛选、分离耐高盐的芽孢杆菌菌株,用功能培养基从中筛选具有促生能力的细菌菌株,用Salkowski比色法定性定量分析其产IAA的能力,采用盆栽试验研究其在盐胁迫条件下对燕麦生长的影响,运用16S rDNA序列分析法对促生效果好的菌株进行鉴定。结果显示,本研究共分离得到13株耐高盐的芽孢杆菌菌株,其中3株芽孢杆菌（YP2、YP4、SM12）可耐受10%（质量分数）的NaCl,且均有解磷、解钾、固氮能力,具有较强的产IAA能力。接种这3株菌株均能在盐胁迫条件下促进燕麦生长,提高其抗盐能力,其中菌株YP2的效果最优,与对照相比,其株高、茎粗、地上部鲜重、总根长、根系总表面积、根尖数分别显著（P<0.05）增加72.02%、42.58%、186.11%、392.35%、378.07%和518.85%,燕麦叶片中的丙二醛含量显著（P<0.05）降低43.34%,叶绿素含量、脯氨酸含量,及过氧化物酶、过氧化氢酶活性分别显著（P<0.05）提高了312.20%、124.10%、274.09%和198.60%。经16S rDNA序列分析,将菌株YP2初步鉴定为弯曲芽孢杆菌（Bacillus flexus）。该菌株作为盐碱地专用生物菌剂具有较大的开发应用潜力。

Screening of salt-tolerant growth-promoting Bacillus strains and their effect on oat growth under salt stress

Abstract: In order to screen salt-tolerant growth-promoting Bacillus strains from the rhizosphere soil of coastal halophytes in Qinhuangdao City, Hebei Province, and provide bacterial resources for the development of salt-tolerant bacterial manure, high-salinity tolerant Bacillus strains were screened and separated by LB culture medium with pH of 9.0 and NaCl mass fraction of 5%, 10%, 15%, respectively. The strains with growth-promoting abilities were further screened by functional medium. Their auxin (IAA)-producing abilities were quantitatively analyzed by Salkowski colorimetric method. The pot experiment was used to study their effect on the growth of oat under salt stress, and 16S rDNA sequence analysis was used to identify the strain with good growth promoting effect. It was shown that a total of 13 Bacillus strains were isolated with high salt tolerance, among which 3 strains (YP2, YP4, SM12) could tolerant 10% (mass fraction) NaCl. All the three strains had abilities of phosphate-solubilizing, potassium-releasing, nitrogen fixation, and production of IAA. Besides, all the three strains could improve the salt resistance of oat and promote its growth under salt stress, and the strain YP2 showed the best performance. Compared with the control, the plant height, stem diameter, shoot biomass, root length, root surface area and root tips quantity were significantly (P<0.05) increased by 72.02%, 42.58%, 186.11%, 392.35%, 378.07% and 518.85%, respectively, malondialdehyde content in oat leaves was significantly (P<0.05) decreased by 43.34%, and the contents of chlorophyll and proline, and activities of peroxidase and catalase were significantly (P<0.05) increased by 312.20%, 124.10%, 274.09% and 198.60%, respectively. As revealed by 16S rDNA sequences, YP2 strain was identified as Bacillus flexus, which has great potential to be developed as a special bacterial agent.