叶片喷施贝莱斯芽孢杆菌提升番薯产量的生理响应及内生菌-代谢通路调控机制

Foliar application of Bacillus velezensis induces physiological responses and increases the yield of sweet potato by regulating the endophyte community structure and metabolic pathways

摘要:

目的 探究贝莱斯芽孢杆菌(Bacillus velezensis) XZT106对番薯的生物刺激效应，明确其提升番薯产量的机制。方法 采用叶片喷施贝莱斯芽孢杆菌发酵液处理植株，以喷施其灭活发酵液处理的植株作为对照。通过分析叶片中的叶绿体含量、叶绿体超微结构及抗氧化相关酶活性，并结合番薯不同生态位的内生菌群落结构及代谢组成，从多维度解析贝莱斯芽孢杆菌菌液处理提升番薯产量的调控机制。结果 叶片喷施贝莱斯芽孢杆菌提高了番薯产量，增强了根部抗氧化酶活性，诱导叶片叶绿体超微结构发生改变，使基质结构更为致密且胞内淀粉颗粒增大。此外，喷施贝莱斯芽孢杆菌菌液使番薯各组织部位内生微生物群落结构发生显著改变，镰孢菌属(Fusarium)的相对丰度均显著降低，而泛菌属(Pantoea)显著富集。同时菌液处理还显著改变了叶片和土壤的代谢组谱。叶片中调控生长和增强抗逆性的核黄素代谢、玉米素生物合成及异黄酮生物合成途径显著上调。土壤中促进侧根发育的轴突再生通路和促进细胞增殖的甘油磷脂代谢通路显著上调。结论 本研究表明贝莱斯芽孢杆菌发酵液通过增强抗氧化能力、改善叶片细胞超微结构、重塑番薯内生菌群结构、激活关键促生与胁迫响应代谢通路共同起到促生效果，为贝莱斯芽孢杆菌微生物制剂在番薯增产中的应用提供了新的理论依据。

Abstract:

Objective To investigate the biostimulatory effects of Bacillus velezensis XZT106 on the tuber crop sweet potato (Ipomoea batatas) and elucidate the potential mechanisms underlying its yield increase.Methods Sweet potato plants were treated by foliar spraying with B. velezensis fermentation broth, with the plants treated with inactivated B. velezensis fermentation broth as the control. We analyzed the chloroplast content, chloroplast ultrastructure, and antioxidant enzyme activity as well as the structure and metabolite composition of endophyte communities in different ecological niches of sweet potato plants to delve into the mechanisms by which B. velezensis fermentation broth increases the sweet potato yield.Results Foliar application of B. velezensis increased the sweet potato yield, enhanced the antioxidant enzyme activity in the roots, induced changes of chloroplast ultrastructure, and led to a more compact matrix structure with enlarged intracellular starch granules. In addition, foliar application of B. velezensis caused significant changes of endophyte community structures in various parts of sweet potato plants, significantly reducing the relative abundance of Fusarium and increasing the relative abundance of Pantoea. Moreover, the foliar application significantly altered the metabolome profiles of leaves and soil. Riboflavin metabolism, zeatin biosynthesis, and isoflavone biosynthesis, which regulate growth and enhance stress resistance, were significantly upregulated in leaves. The axon regeneration pathway promoting lateral root development and the glycerophospholipid metabolism pathway promoting cell proliferation were significantly upregulated in soil.Conclusion B. velezensis fermentation broth exerts a plant growth-promoting effect by enhancing antioxidant capacity, improving leaf cell ultrastructure, reshaping the endophyte community structure, and activating key growth-promoting and stress response metabolic pathways in sweet potato plants. These findings provide a new theoretical foundation for the application of B. velezensis-based microbial inoculants in enhancing the sweet potato yield.