一株维罗尼假单胞菌D15对水稻种子萌发及秧苗素质的影响

Effects of Pseudomonas veronii D15 on rice seed germination and seedling quality

摘要:

背景 植物内生细菌(plant endophytic bacteria)是一类定殖于健康植物组织内部、不引起明显病害症状的微生物，具备促进植物生长、增强抗病性及耐受非生物胁迫等多重功能，是可持续农业中具有重要应用潜力的微生物肥料种质资源。目的 从大庆苏打盐碱地水稻根中分离内生细菌，对其进行鉴定并评价其促生潜力，为秧苗促生菌剂提供资源。方法 采用稀释涂布法对内生菌进行分离，通过形态观察及16S rRNA基因测序进行菌株鉴定；通过促生性能试验、水稻种子萌发与育苗试验评估菌株促生性能。结果 基于16S rRNA基因构建的系统发育分析初步鉴定菌株D15为维罗尼假单胞菌(Pseudomonas veronii)。促生特性检测结果发现该菌株IAA分泌量为9.39 μg/mL，溶无机磷量为12.78 mg/L，固氮酶活性为193.37 pmol/(mL·h)；产铁载体可溶性指数(D/d值)为1.60、解蛋白可溶性指数(D/d值)为1.08、苏打盐耐受浓度达100 mmol/L (Na₂CO₃:NaHCO₃=1:9)；种子萌发实验发现，菌株D15菌悬液使萌发种子的苗高及根长显著提高8.58%和7.76%。施加10⁹ CFU/mL菌悬液的水稻育苗二叶一心时期试验组较对照组苗高和茎基宽显著提升了23.10%和10.15%，显著提高了秧苗的充实度、壮苗指数、根部连接数、节点数、根尖数、分叉数和交叉数，分别增加了24.86%、54.01%、46.26%、43.03%、36.05%、45.25%和56.02%；三叶一心时，上述指标仍保持显著提升，苗高、根长和茎基宽分别增加16.90%、29.50%和25.18%，同时秧苗的充实度、壮苗指数、根部连接数、节点数、根尖数、分叉数和交叉数显著提高了17.87%、54.40%、33.16%、44.55%、44.64%、24.47%和34.62%。结论 从水稻根系分离获得的内生细菌P. veronii D15具有良好的促生性能，具备开发微生物肥料的潜力。

Abstract:

Background Plant endophytic bacteria are a type of microorganisms that colonize the internal tissues of healthy plants without causing obvious disease symptoms. They possess multiple functions such as promoting plant growth, enhancing disease resistance and tolerance to abiotic stress, and are a microbial fertilizer germplasm resource with significant application potential in sustainable agriculture.Objective To isolate and identify endophytic bacteria from the roots of rice grown in Daqing soda saline-alkali soil, and to evaluate its plant growth-promoting potential, thereby providing a resource for seedling inoculants.Methods Endophytic bacteria were isolated by the dilution-plating method and identified through morphological observation and 16S rRNA gene sequencing. The plant growth-promoting capacity of the target strain was evaluated via plant growth-promoting assays as well as rice seed germination and seedling cultivation experiments.Results Phylogenetic analysis based on the 16S rRNA gene preliminarily identified strain D15 as Pseudomonas veronii. The strain could produce 9.39 μg/mL indole-3-acetic acid, solubilize 12.78 mg/L inorganic phosphate, and exhibit nitrogenase activity of 193.37 pmol/(mL·h). The siderophore and protease solubility indices (D/d) were 1.60 and 1.08, respectively. The strain could tolerant soda-salt (Na₂CO₃:NaHCO₃=1:9) at the concentration of 100 mmol/L. In seed-germination assays, inoculation with the cell suspension of strain D15 significantly increased the shoot height and root length of germinated seeds by 8.58% and 7.76%, respectively. Rice seedlings treated with 10⁹ CFU/mL D15 exhibited significant increments of 23.10% and 10.15% in shoot height and stem-base width, respectively, compared with the control at the two-leaf-and-one-bud stage. In addition, the inoculation increased the seedling fullness, vigorous-seedling index, root links, nodes, root tips, forks, and crossings by 24.86%, 54.01%, 46.26%, 43.03%, 36.05%, 45.25%, and 56.02%, respectively. These beneficial effects persisted until the three-leaf-and-one-bud stage, at which the shoot height, root length, and stem-base width increased significantly by 16.90%, 29.50%, and 25.18%, respectively, compared with those of the control. Meanwhile, the seedling fullness, vigorous-seedling index, root links, nodes, root tips, forks, and crossings improved significantly by 17.87%, 54.40%, 33.16%, 44.55%, 44.64%, 24.47%, and 34.62%, respectively.Conclusion The endophytic bacterium P. veronii D15, isolated from rice roots, exhibits excellent plant growth-promoting characteristics and shows the potential for development as a microbial biofertilizer.