烤烟K326与香料植物间作模式下根际土可培养细菌多样性及功能

Diversity and function of culturable rhizospheric bacteria of flue-cured tobacco K326 intercropped with five spice plants

【背景】烤烟是我国重要的经济作物,选择间作种植方式能影响根际微生物的多样性,缓解烤烟连作障碍;根际微生物能够适应根际微环境的变化,对烤烟的生长具有一定促进作用。【目的】研究不同生长时期烤烟K326与5种香料植物间作模式下烤烟根际土细菌种群多样性,从生物多样性角度比较不同时期、不同间作模式的差异,探究烤烟根际微生物的适应性及功能。【方法】以不同生长期、不同香料植物间作模式下烤烟根际土为研究对象,设计纯培养方法对根际细菌进行分离及16S rRNA基因测序,研究不同种植期、不同间作模式下根际土细菌多样性,并挑选代表菌株进行烟碱、Cr6+耐受及促生性质检测。【结果】蕾薹期、开花结果期、采摘期烤烟K326与5种香料植物间作模式下植物根际土蕴含丰富的细菌资源,共分离到707株细菌,分布于70个属。蕾薹期烤烟根际土细菌的香农指数变化为:W(4.0791917)>2GAY(3.8403521)>2GDY(3.5145628)>2GCKY(3.4977034)>2GBY(3.4474789)>2GCY(3.2534092)>2GEY(3.2411034);开花结果期烤烟根际土细菌的香农指数变化为:3GAY(3.6889817)>3GCKY(3.4421251)>3GBY(3.3531558)>3GDY(3.3491719)>3GEY(3.3062945)>3GCY(3.3055822);采摘期烤烟根际土细菌的香浓指数变化为:5GEY(2.8571028)>5GBY(2.4583113)>5GAY(2.2718685)>5GCKY(2.2102536)>5GCY(2.0794415)>5GDY(0.6931472);在不同时期都检测到的细菌类群有节杆菌属(Arthrobacter)、芽胞杆菌属(Bacillus)、短波芽孢杆菌属(Brevibacillus)、短波单胞菌属(Brevundimonas)、微杆菌属(Microbacterium)、类诺卡氏菌属(Nocardioides)、假单胞菌属(Pseudomonas)、红球菌属(Rhodococcus)、链霉菌属(Streptomyces)和地杆菌属(Terrabacter),大部分代表菌株具有烟碱耐受、Cr6+耐受、固氮、铁载体产生、溶磷、淀粉水解等特性。【结论】不同生长时期、不同间作模式的烤烟根际土中蕴含丰富的细菌类群,Bacillus、Pseudomonas和Streptomyces是烤烟根际土中的优势类群,在烟碱、Cr6+耐受及促生作用方面具有重要应用潜力;香料植物与烤烟间作模式能够改变根际土细菌的多样性;在开花结果期,5种香料植物与烤烟的间作明显增加了土壤根际土可培养细菌的多样性;薄荷、香茅草、香叶天竺葵间作类型在缓解烤烟连作障碍方面具有优势。

[Background] Flue-cured tobacco is an important economic crop in China. Intercropping affects the diversity of rhizospheric microorganisms and alleviates the production of flue-cured tobacco. Rhizospheric microorganisms can adapt to changes in the rhizosphere microenvironment, which promotes the growth of flue-cured tobacco. [Objective] We examined the diversity of the bacterial population in flue-cured tobacco’s rhizosphere soil under the intercropping models between tobacco K326 and five spice plants at different growth periods. In addition, we compared the variances in intercropping models in various growing periods from the perspective of biological diversity and subsequently screened the adaptability and functional characteristic of typical rhizosphere bacterium. [Methods] Soil samples from various growing periods with different intercropping patterns were collected. We designed the culturing method to isolate and sequence the 16 S rRNA gene, and calculated the diversity index. Representative strains were selected to detect nicotine and Cr6+ tolerance as well as growth-promoting properties. [Results] A total of 707 bacterial strains distributed in 70 genera were isolated. The change of the Shannon index of bacteria in flue-cured tobacco’s rhizosphere soil at the stem elongation period was W(4.079 191 7)>2 GAY(3.840 352 1)>2 GDY(3.514 562 8)>2 GCKY(3.497 703 4)>2 GBY(3.447 478 9)>2 GCY(3.253 409 2)>2 GEY(3.241 103 4). The change of Shannon index of bacteria in flue-cured tobaccos’ rhizosphere soil at the leaf ripening period was 3 GAY(3.688 981 7)>3 GCKY(3.442 125 1)>3 GBY(3.353 155 8)>3 GDY(3.349 171 9)>3 GEY(3.306 294 5)>3 GCY(3.305 582 2). The change of Shannon index of bacteria in flue-cured tobacco’s rhizosphere soil at the harvesting period was 5 GEY(2.857 102 8)>5 GBY(2.458 311 3)>5 GAY(2.271 868 5)>5 GCKY(2.210 253 6)>5 GCY(2.079 441 5)>5 GDY(0.693 147 2). The genera Arthrobacter, Bacillus, Brevibacillus, Brevendimononas, Microbacterium, Nocardioides, Pseudomonas, Rhodococcus, Streptomyces and Terrabacter were detected at all the three growth periods. Majority of the representative strains exhibit positive activities for nicotine tolerance, Cr6+ tolerance, nitrogen fixation, siderophore production, phosphorus solubilization and starch hydrolysis. [Conclusion] Rhizosphere soil contained abundant bacterial resources under the intercropping mode between five spice plants and the flue-cured tobacco K326. Among the dominant bacterial groups in flue-cured tobacco’s rhizosphere soil, the genera Bacillus, Pseudomonas and Streptomyces have potential applicability in nicotine tolerance, Cr6+ tolerance and growth-promoting effects. The intercropping can change the diversity of bacteria in rhizosphere soil of flue-cured tobacco. In the tobacco leaf ripening period, the intercropping of five spice plants and flue-cured tobacco significantly increased the diversity of cultivable bacteria in the rhizosphere soil. The intercropping types of Monarda didyma, Cymbopogon citratus and Pelargonium graveolens own advantages in relieving continuous cropping of flue-cured tobacco.