花生根际促生复合菌剂对连作花生生理生化指标和根际细菌群落的影响

Effects of a compound inoculant of peanut growth-promoting rhizobacteria on physiological and biochemical indexes of peanut plants in a continuous cropping system and rhizosphere bacterial community

摘要:

【目的】利用多功能根际促生菌剂促进花生生长，缓解连作障碍对花生的生长抑制。【方法】从10年连作花生根际土中筛选根际微生物，测定其促生及拮抗能力，并经16S rRNA基因测序确定菌株分类。选取3株功能互补且相互之间无生长抑制的根际促生菌制备微生物复合菌剂，利用发芽及盆栽试验验证微生物复合菌剂的促生效应。利用高通量测序技术对花生根际土壤细菌的16S rRNA基因的V3-V4区进行测序分析。【结果】从连作花生根际中共筛选获得37株具有促生及抑制植物病原菌生长能力的根际促生菌，选取3株制备微生物复合菌剂。与空白对照相比，复合菌剂显著提升花生发芽率13.22%；与单独使用根际促生菌相比，复合菌剂显著提升花生发芽率分别为6.99%、7.51%、8.87%。施用复合菌剂对花生根系形态、根瘤数量、叶绿素含量、植株光合参数和植株抗氧化酶活均有显著促进作用，花生根系总长、根尖数、主根直径、根系体积和根系活力分别增加了43.50%、49.31%、15.11%、16.92%和112.16%；花生苗期、花针期叶片叶绿素含量和光合作用均得到显著的提高；花生根瘤数量每株增加34个。施用复合菌剂后对花生的根际细菌多样性影响并不显著，在门水平上的优势菌门变形菌门(Proteobacteria)、放线菌门(Actinobacteriota)和拟杆菌门(Bacteroidota)占70%以上。在属水平上新鞘氨醇菌属(Novosphingobium)和鞘氨醇单胞菌属(Sphingomonas)是优势菌属。【结论】本研究研制的花生根际促生复合菌剂可有效促进花生种子发芽、花生根系生长、提高叶片叶绿素含量以及促进植物光合作用，为缓解花生连作障碍及丰产增收提供有效的技术支持。

Abstract:

[Objective] To apply multifunctional plant growth-promoting rhizobacteria to enhance peanut growth and mitigate the inhibitory effects caused by continuous cropping. [Methods] Plant growth-promoting rhizobacteria were screened from the rhizosphere soil of peanut plants in a system with continuous cropping for ten years, and their growth-promoting and antagonistic abilities were determined. The strains were identified by 16S rRNA gene sequencing. Three plant growth-promoting rhizobacterial strains with complementary functions and no growth inhibition between each other were selected to prepare a compound microbial inoculant, the plant growth-promoting effect of which was examined by seed germination and pot experiments. High-throughput sequencing was carried out for the V3–V4 region of bacterial 16S rRNA gene. [Results] A total of 37 plant growth-promoting rhizobacterial strains capable of promoting plant growth and inhibiting pathogen growth were screened from the rhizosphere of peanut plants in a continuous cropping system. Three strains were selected to prepare the compound inoculant. Compared with the blank control, the compound inoculant increased the germination rate of peanut by 13.22%. Compared with the treatments with the three strains alone, the compound inoculant increased the germination rate by 6.99%, 7.51%, and 8.87%, respectively. The application of the compound inoculant had significant promoting effects on the root morphology, number of nodules, chlorophyll relative content (SPAD), photosynthetic parameters, and antioxidant enzyme activity of peanut plants. Specifically, it increased the total root length, number of root tips, taproot diameter, root volume, and root activity by 43.50%, 49.31%, 15.11%, 16.92%, and 112.16%, respectively. The application of the compound inoculant significantly increased the leaf SPAD value and promoted the photosynthesis of peanut plants at seedling stage and flowering stage. Furthermore, it increased the number of root nodules by 34 nodules per plant. However, the application of the compound inoculant had no significant effect on the bacterial diversity in peanut rhizosphere. The dominant phyla were Proteobacteria, Actinobacteriota, and Bacteroidota, accounting for more than 70%. Novosphingobium and Sphingomonas were the dominant genera. [Conclusion] The compound inoculant of plant growth-promoting rhizobacteria improved the seed germination, root growth, leaf SPAD value, and photosynthesis of peanut plants, providing technical support for alleviating continuous cropping obstacles and promoting the healthy growth of peanut plants.