【作者】 湛方栋；

【导师】 黄建国； 唐远驹；

【作者基本信息】 西南农业大学 ， 微生物学， 2004， 硕士

【摘要】 德国科学家Lorenz Hiltner在1904年首先提出了根际（Rhizosphere）的概念，用于描述植物根系周围的微区土壤。在根际微区内，植物、土壤和微生物相互作用，土壤的理化和生物学特性显著不同于非根际土壤，是一个极其特殊的土壤生态系统。值得注意的是，根际微生物的数量、活性和群落结构也不同于非根际土壤，它们与植物的养分吸收、土壤养分的生物有效性和土传病害的发生密切相关。 青枯菌（Ralstonia solanacearum）主要存在于根际土壤，是引起烟草青枯病的病原微生物，并在世界范围内严重危害烤烟生长，在我国西南地区尤其严重。贵州省是我国重要的烤烟生产基地，而黄壤又是当地的主要地带性土壤。但是，在黄壤上种植烤烟，青枯病发病率极高，严重地影响烤烟的生产。因此，研究烤烟青枯病发病机理，找出解决办法，不仅可以丰富生态病理学的理论和实践，同时对当地烤烟生产的可持续发展也有重要意义。 试验选择贵州省三种典型、具有代表性的植烟土壤为研究对象，它们是砂岩发育的黄壤、石灰岩发育的黄色石灰土和泥岩发育的中性紫色土。在烤烟生长的团棵期、现蕾期和成熟期，田间采集根际土壤，研究了根际微生物群落结构和数量动态变化。目的是为防控烤烟青枯病，了解根际土壤中的养分转化，以及烤烟的科学管理提供基础资料与理论依据。试验结果表明： 1．烤烟根际微生物的数量细菌＞放线菌＞真菌，其数量范围分别为10⁹-10¹⁰、10⁷-10⁹和10⁴-10⁶CFU·g^-1干土。此外，土壤类型不同，根际细菌和放线菌的数量也不一样，黄壤＞黄色石灰土＞中性紫色土，黄壤和中性紫色之间的差异达到显著水平（p＜0.05）。在不同土壤中，真菌的数量差异未达显著水准，但仍存在中性紫色土＞黄壤＞黄色石灰土的趋势。 2．在烤烟生长过程中，根际微生物的数量随生育时期不同而变化。细菌在团棵期最少，然后逐渐增加，现蕾期达到峰值，进而又缓慢减少；放线菌和真菌数量从团棵期到成熟期呈增长趋势。 3．比较三种根际微生物，细菌数量的变幅最大。土壤不同，根际微生物数量的变幅也不一样。黄色石灰土中的细菌和真菌变幅最大；黄壤中的放线菌变幅最大；在中性紫色土中，细菌、真菌和放线菌的变幅均最小。 4．烤烟根际微生物的种群十分丰富，共分离获得了165株细菌、123株放线菌和100株真菌，有331个株菌鉴定到属，涉及细菌14个属，真菌11个属，放线菌是链霉菌属的8个类群，另有57个株菌未能确切鉴定。西南农业大学硕士学位论文摘要5.在不同根际土壤中，细菌、放线菌和真菌优势种群的组成具有一致性。在19株优势细 菌中，有11株为假单胞杆菌:在14株优势真菌中，有”株为青霉属:优势放线菌均 为链霉菌属。不过，在不同土壤中，烤烟根际中的优势细菌和放线菌组成有一定差异。 作为优势种群，芽抱杆菌属和气单胞菌属只存在于中性紫色土中，产碱菌属只存在于 黄壤和黄色石灰土中，白抱类群存在于中性紫色土中，吸水类群存在于黄色石灰土中， 但黄壤中的放线菌优势种群不明显。6.就土壤类型而言，在中性紫色土中，细菌和放线菌的种群多样性大于其余两种土壤; 真菌种群多样性为黄壤>黄色石灰土>中性紫色土。就烤烟生育期而言，烤烟根际微 生物种群多样性变化在不同土壤中表现不同。在黄壤和黄色石灰土中，细菌种群多样 性随生育进程的推进而不断下降:在中性紫色土中，从团棵期到现蕾期上升，然后下 降。真菌的种群多样性的变化规律是:在中性紫色土和黄壤中，从团棵期到现蓄期增 加，而后减小:在黄色石灰土中，成熟期最大。但是，根际放线菌种群多样性变化在 三种土壤上表现各不相同。此外，在中性紫色土中，根际细菌和放线菌种群多样性变 幅最小:在黄色石灰土中，细菌种群多样性变幅最大:在黄壤中，放线菌种群多样性 变化最大，真菌种群多样性在三种土壤上的变化相似。7.在烤烟现蕾期，从黄壤根际中分离出具有强烈致病性的烟草青枯病病原菌（彻Istonia solanacearum）。在烤烟根际中，我们还分离出巧个具有平板拮抗Ralstonia s。勿”口‘earum活性的菌株，它们主要存在于现蕾期和成熟期的黄壤和黄色石灰土中。 其中3株为细菌、3株为放线菌，9株为真菌。在9株真菌中，有5株为木霉属真菌。更多还原

【Abstract】 Rhizosphere was firstly termed by Lorenz Hilter, a Germany scientist, in 1904, to describe the soil micro-environment around plant roots. Plants, soils and microorganisms interacted intensively in the rhizosphere, resulting in great variation in physical, chemical and biological characteristics compared to non-rhizosphere soil. It is necessary to point out that rhizosphere differs in the amounts, actives and community structures of microorganisms from non-rhizosphere one, which influences plant nutrient absorption, soil nutrient bioavailability and soil-borne diseases occurrence.Ralstonia solanacearum, which exists in rhizosphere soils, was the pathogen of tobacco bacterial wilt. The disease severely harmed the tobacco growth in the world, especially in Southwest China. Guizhou was an important tobacco producing province in China, widespread yellow earths, the main zonal soils. The occurrence of tobacco bacterial wilt was, however, high in the yellow earths, which reduced largely tobacco yields. The present experiment was carried out to reveal the occurrence mechanism of tobacco bacterial wilt in order to obtain some information on the theories and practices of ecological pathology and sustainable tobacco production in Guizhou.Three typical and representative tobacco cultivated soils were selected from Guizhou province for experiment, which were yellow earths derived from sandstone, yellow rendzina from limestone and neutral purplish soils from mudstone, respectively. In the stages of rosette, budding and mature during tobacco period, rhizosphere soils were sampled from fields for studying microorganisms. The objectives were to offer fundamental data and theory for (i) controlling tobacco bacterial wilt, (ii) understanding nutrient convert in rhizosphere and (iii) scientific field managements. Following were results obtained:1 . The amount of microorganisms in tobacco rhizosphere varied in the sequence: bacteria (109-1010 CFU.g-1 dry soil) > actinomycetes (107-108 CFU.g-1 dry soil) > fungi (104-106 CFU.g-1 dry soil). In addition, the amount of rhizosphere bacteria and actinomycetes differed among soil types in accordance with yellow earth > yellow rendzina > neutral purplish soil. Moreover, Significant differences of rhizosphere bacteria and actinomycetes were found between yellow earth and neutral purplish soil (p<0.05). Even though no significant variation of fungal amount was observed among three soils, there still existed the tendency: i.e. neutral purplish soils>yellow earths>yellow rendzina.2.The amount of rhizosphere microorganisms changed with growth periods of tobacco. The bacteria were the lowest in rosette stage and then increased till budding. Thereafter, they decreased gradually. But actinomycetes and fungi showed the tendency that increased from rosette stage to mature.3.Bacteria changed most obviously compared to actinomycetes and fungi in the rhizosphere of tobacco. The number of rhizosphere microorganisms varied among soils. The bacteriaand fungi in rhizosphere of tobacco fluctuated greatly in yellow rendzina, while actinomycetes in yellow earths. Bacteria, actinomycetes and fungi changed least in neutral purplish soil compared to other two soils.4.The microorganisms in the rhizosphere of tobacco were rich in populations, 165 bacteria, 123 actinomycetes and 100 fungi were isolated, among which genus of 331 strains was identified.. They were 14 genuses of bacteria, 11 genuses of fungi and 8 groups in Streptomyces of actinomycetes. 57 strains couldn’t be identified.5.Dominant populations of bacteria, actinomycetes and fungi showed similarly in tobacco rhizosphere in three soils. 11 of 19 dominant bacteria strains were Pseudomonans, 11 of 14 dominant fungi strains Penicillium and all dominant actinomycetes strains Streptomyces. Additionally, some differences were detected in dominant strains of bacteria and actinomycetes in tobacco rhizosphere soils. Bacillus and Aemmonas, the dominant populations, were found only in neutral purplish soils. Alcaligenes wer更多还原