东北早晚熟菜豆根际与根瘤微生物差异及根瘤菌固氮能力

Differences of rhizosphere and root nodule microorganisms between early and late maturing varieties of Phaseolus vulgaris in northeast China and nitrogen-fixing capacity of rhizobia

摘要:

菜豆(Phaseolus vulgaris L.)是全球最为重要的食用豆类之一，根际微生物与植物互惠互利，同时也是促进作物生长及健康的重要因素，然而，如何利用豆类植物微生物组促进作物生长的探索尚显不足。目的 分析紫冠与巨冠菜豆的根际与根瘤细菌群落结构与功能的差异；筛选根瘤菌并探究其固氮和促生性能。方法 利用16S rRNA基因测序技术，分析2种菜豆根际与根瘤细菌的差异；采用平板划线法筛选根瘤菌，利用无氮蛭石盆栽试验对11株根瘤菌的固氮性能及促生效果进行评估。结果 巨冠菜豆的根际土壤细菌群落多样性显著低于紫冠菜豆，同时2种菜豆根际样品中细菌多样性显著高于根瘤样品。此外，菜豆根际富集了根瘤菌属(Rhizobium)、鞘氨醇单胞菌属(Sphingomonas)、伯克霍尔德氏菌属(Burkholderia)等有益菌属。其中，Rhizobium是2种菜豆根瘤中的优势菌属。Gephi网络分析表明，根际与根瘤细菌群落呈正相关，占比分别为75.52%和86.67%；PICRUSt2功能预测结果表明，菜豆根际细菌群落中碳水化合物、氨基酸和脂质代谢等功能丰度较高，且具有较高的氮代谢功能基因丰度。无氮蛭石盆栽试验表明，Rhizobium lusitanum NZ5和R. etli GLJ10显著增加了紫冠菜豆地下干重，分别增加了43.21%和48.15%；R. lusitanum NZ5、R. etli GLZ1和R. changzhiense GLJ12能显著增加巨冠菜豆地下干重，分别增加了77.37%、68.42%和67.37%。结论 菜豆能够选择性地从土壤中富集多种微生物，在其根际建立一个紧密协同且功能强大的微生物群落，且接种不同根瘤菌对菜豆的促生效果存在差异。

Abstract:

Phaseolus vulgaris L. is one of the key edible legumes in the world. Rhizosphere microorganisms have mutually beneficial interactions with plants, being important factors promoting crop growth and health. However, studies are limited regarding how to utilize the microbiomes of legumes to promote crop growth.Objective To investigate the structural and functional differences of microbial communities in the rhizosphere and root nodules between two varieties (‘Ziguan’ and ‘Juguan’) of P. vulgaris, screen rhizobial strains, and evaluate their nitrogen-fixing and growth-promoting properties.Methods We employed 16S rRNA gene sequencing to analyze the bacterial community structures in the rhizosphere and root nodules of the two varieties. The rhizobial strains were screened by the plate streaking method. Pot experiments with nitrogen-free vermiculite were carried out to evaluate the nitrogen-fixing performance of the 11 rhizobial strains screened out.Results The bacterial diversity in the rhizosphere soil of ‘Juguan’ was significantly lower than that of ‘Ziguan’, and the bacterial diversity in the rhizosphere soil samples of both varieties was significantly higher than that in the root nodule samples. In addition, the rhizosphere of P. vulgaris harbored beneficial bacterial genera such as Rhizobium, Sphingomonas, Burkholderia, among which Rhizobium was dominant in the root nodules of both varieties. Gephi network analysis showed that bacterial communities in the rhizosphere and root nodules had positive correlations, with the relative abundance of 75.52% and 86.67%, respectively. PICRUSt2 function prediction indicated that the bacteria in the rhizosphere mainly had the functions related to carbohydrate, amino acid, and lipid metabolism, with abundant genes involved in nitrogen metabolism. Pot experiments showed that Rhizobium lusitanum NZ5 and R. etli GLJ10 increased the underground dry weight of ‘Ziguan’ by 43.21% and 48.15%, respectively. R. lusitanum NZ5, R. etli GLZ1, and R. changzhiense GLJ12 increased the underground dry weight of ‘Juguan’ by 77.37%, 68.42%, and 67.37%, respectively.Conclusion P. vulgaris possesses ability to selectively enrich a variety of microorganisms in the soil, establishing a closely coordinated and highly functional microbial community in the rhizosphere. Moreover, different rhizobial strains exerted varied growth-promoting effects on P. vulgaris.