棉花根际促生细菌的研究进展

综述了根际促生细菌(PGPR)的概念、研究手段、基因标记技术和荧光原位杂交技术在研究棉花根际促生细菌中的应用.植物根系可以分泌各种对微生物有益的物质,吸引微生物在根际的聚集.棉花凝集素对根际促生细菌菌株的胞外多糖具有凝集作用,在棉花根际促生细菌与棉花根部相互识别过程中具有重要作用,可以利用棉花凝集素作为筛选工具筛选对棉花具有促生作用的根际促生细菌菌株.基因标记技术证明棉花根际促生细菌能高密度地定殖在棉花根部,对棉花的生长起促进作用,并能抑制某些植物病原菌及根际有害微生物.分子生物学技术在微生物生态学领域的应用促进了棉花根际促生细菌的研究和应用,可以利用棉花根际促生细菌研发微生物肥料.     

一株克锡勒氏菌对小麦苗期的促生耐盐效应研究

土壤盐渍化已经成为全球重要的生态环境问题之一,农业生态系统中土壤盐分增加会影响作物生长发育、导致减产。近年来,随着微生物组学研究的深入,微生物提升植物抗逆性功能认识的加深,生物肥料开始应用于盐碱地植物修复中。为探究根际促生菌在高盐环境中对小麦生长及代谢的影响,本文选取一株分离自盐地碱蓬根际土中、具有耐盐和分泌植物生长素功能的克锡勒氏细菌(Kushneria indalinina JP-JH),选取耐盐小麦品种‘小偃60’,在无盐(0 mmol·L~(-1))、低盐(200 mmol·L~(-1))和高盐(400 mmol·L~(-1))的水培条件下接种耐盐促生菌JP-JH,分析其对小麦苗期生长及根系分泌有机酸的影响。培养40 d后,在无盐、低盐、高盐条件下,接种JP-JH组小麦幼苗鲜重显著高于未接种对照组(P0.05);在无盐、低盐时,接菌组的小麦幼苗干重显著高于对照组(P0.05);且在高盐胁迫时,接菌组株高显著高于对照处理(P0.05)。在无盐条件下,接菌未对小麦幼苗根系分泌的6种有机酸产生显著影响;在盐胁迫(低盐以及高盐)条件下,接菌显著提高了根系分泌草酸和酒石酸含量(P0.05)。上述结果表明耐盐促生菌能够在苗期促进小麦的生长发育,且对根系分泌的部分有机酸产生了显著影响,草酸和酒石酸可能在微生物-植物互作中具有重要作用。本研究揭示了细菌K. indalinina JP-JH对小麦的耐盐促生效应以及对根系分泌有机酸的影响,为开发具有提升小麦耐盐促生功能的生物肥料提供理论依据和菌种资源。     

植物根际促生菌促进小麦生长及提高其抗旱性的研究进展

干旱胁迫是影响小麦生长发育与产量形成最主要的非生物胁迫因子,近年来化肥的过量使用及全球气候变化产生的不利影响,导致小麦在生长过程中受到的干旱胁迫危害日趋严重。植物根际促生菌(PGPR)不仅可以协助小麦提高养分利用率,促进其生长发育,还能够通过自身作用或产生多种代谢产物协助小麦抵御干旱胁迫。本文归纳总结了PGPR促进小麦生长及提高其抗旱性的研究进展,为利用PGPR提高小麦促生抗旱的研究奠定了理论基础。     

根际促生菌防控土传病害的机理与应用进展

根际促生菌作为一类活跃于植物根际的有益微生物,对抑制土传病害的发生,改善和维护土壤生态质量具有重要作用以及广阔的发展前景。本文综述了根际促生菌直接或间接的土传病害防控机理,包括产抗生素、产水解酶、释放挥发性气体、诱导抗性、分泌铁载体、分泌激素和固氮解磷等;亦从信号识别与迁移、定殖规律以及定殖的微生物群落影响等方面对根际促生菌的定殖防病机理予以了总结;此外,笔者还就根际促生菌的应用现状进行了概述。     

植物根际沉积与土壤微生物关系研究进展

【目的】活跃的根际微生物被喻为植物的第二套基因组,在植物的生长发育过程中发挥着关键作用。植物通过根际碳沉积影响根际土壤微生物群落的结构和功能;作为根际微生态系统中的物质流、能量流和信息流,根际碳沉积是连接大气、植物和土壤系统物质循环的重要纽带;因此,理解根际碳沉积在根际微生态中的作用对于提高植物抗逆性,增加作物产量,调控根际养分循环等方面具有重大的理论意义。【主要进展】本文就近年来关于根际微生物领域的研究成果,重点综述了根际微生物多样性和组学研究;根际碳沉积的组成和产生机理;根际微生物群落结构的形成机制;根际微生物在促进作物养分吸收、提高作物抗逆性等方面的生态功能;以及气候变化和长期施肥对植物-微生物互作关系的影响。在此基础上我们提出了未来可能的研究重点和发展方向:1)植物根际沉积物原位收集方法和检测技术的改进和发展;2)稳定同位素探针与分子生态学技术的结合,将植物、土壤和微生物三者有机地联系起来,综合分析根际界面中微生物的活性与功能;3)高通量测序、组学技术和生物信息学等新技术的引入势必使根际微生物学研究发生革命性的变化;4)随着全球气候变化和土壤肥力改变,例如全球变暖、CO2浓度升高和长期施用化肥,根际沉积物在植物-土壤-微生物中的分配与调节机制,以及这种环境选择压力下植物如何诱导根际促生菌发挥更大作用。希望通过平衡作物与微生物之间的相互关系来实现作物的高产高效,促进农田的可持续利用。     

植物的生化互作现象

Molisch(1937)首先将“Allelopathy”定义为“所有植物类型,包括微生物之间抑制和促进的生化互作”^[1],但后来大多数研究者的工作集中在植物、微生物的代谢产物对其它植物、微生物的抑制效应方面,因此,许多人习惯于将“Allelopathy”理解为“由一种植物(或微生物)释放到环境中的代谢物质引起的直接或间接的不利效应。     

植物益生木霉-根系互作机制及其信号物质筛选策略

木霉作为典型的植物益生真菌已被广泛用于农业绿色生产，并表现出良好的应用前景，它们能够通过产生信号物质与植物根系互作，包括在植物根表和根内定殖、调控植物根系发育、促进养分吸收利用等。木霉基因组中含有大量天然活性物质生物合成基因簇，产生丰富的胞外次级代谢产物，在木霉与植物根系建立互惠关系、稳定促生中发挥了至关重要的作用。目前常用的筛选策略主要是生物活性导向策略和基因组挖掘策略，筛选到的木霉次级代谢产物主要包括植物激素类物质和小分子化合物，物质种类单一，化学结构和调控机制缺乏新颖性，且互作植物主要为模式植物拟南芥，这些因素共同限制了木霉–植物根系互作研究的基础理论突破及其在农业生产中的实际应用。因此将木霉新型天然活性产物的筛选研究与绿色农业发展相结合，符合我国“少投入、多产出、保护环境”的发展模式，是我国实现绿色农业可持续发展的重要机遇和挑战。     

根际促生菌及其在污染土壤植物修复中的应用

植物对重金属吸收、转运和积累以及植物生物学特征使其成为修复重金属污染土壤的重要手段之一。然而,由于植物对重金属的耐受性有限而限制其广泛实际应用,因而探讨植物修复技术强化措施就显得尤为重要。随着自然资源的开发和技术的发展,微生物调控使植物修复技术变得更为可行和更有价值。回顾近年来新兴的微生物调控技术,植物根际促生菌资源因其对环境无污染,可利用自身的抗性系统减缓重金属对植物的毒性,促进植物的生长和影响重金属的迁移等优势,在修复过程中发挥着重要作用。目前,国内外就植物根际促生菌的筛选、鉴定和应用价值等方面已经做了大量的相关研究。本文综述了根际促生菌-植物相互作用的机制及其促进植物修复重金属污染土壤的作用原理。     

天然糖类促生诱抗剂的研究进展

糖类在自然界中广泛存在,部分糖类具有调节植物生长发育和提高植物抗性等功能,是一类安全、环保的植物生理活性物质。基于此,综述了天然糖类调节植物生长发育以及提高植物抗病能力、抗盐能力、抗旱能力、抗重金属能力、抗寒能力和抗酸能力等方面的研究进展,为天然糖类促生诱抗剂的开发及在农业生产上的应用提供理论依据。     

溶磷微生物及其对植物促生作用的研究进展

磷是植物生长发育的必需营养元素之一,主要以难溶性磷化物形式存在于土壤中,难以被植物直接吸收利用。溶磷微生物作为土壤磷循环中的重要组成一员,能通过酸化、酶解等作用将难溶性磷转化分解为可供植物吸收利用的可溶性磷素,进而提高植物对土壤磷素的利用率,被普遍认为是能促进植物生长的一类重要有益微生物。对溶磷微生物的种类、生态分布特征、溶磷能力检测、溶磷影响因素、溶磷机制以及促生应用现状进行了系统综述,并结合目前溶磷微生物在实际应用中存在的问题,对今后的研究方向进行了展望。     

利用微生物防除根寄生杂草列当

根寄生杂草列当(Orobanche spp.)已经严重制约全球许多地区的农业发展,寻找有效防除措施迫在眉睫。由于列当具有特殊生活史且与寄主关系密切,常规防除杂草措施难以达到理想防效。目前,尚无既能有效防除列当又不对寄主造成危害且便于大规模推广应用的列当防除措施。在众多列当防除措施中,微生物防除越来越引起关注和重视。本文对微生物防除列当的国内外研究进展及防除机理进行了综述。目前,列当生防微生物的研究主要集中在镰刀菌(Fusarium spp.)等列当病原菌和根瘤菌(Rhizobium spp.)等列当寄主植物共生菌上。微生物防除列当的机制主要包括两方面:一是通过产生代谢产物直接影响列当的萌发和生长,或通过降解列当种子萌发诱导物质间接影响列当的萌发;二是通过提高寄主植物自身对列当的抗性间接影响列当的寄生和生长。此外,本文还重点介绍了植物土传病害的土壤拮抗微生物防除列当杂草的可行性及研究进展。植物土传病害病原菌和列当均首先通过在地下侵染作物的根系进而危害作物正常生长,而作物抗土传病害的机理也与抗列当的机理类似。因此,存在于土壤中具有防治植物土传病害能力的微生物可能也具有防除根寄生杂草列当的功能。本团队前期试验从植物土传病害的土壤拮抗微生物中筛选到在盆栽试验中能够有效防除向日葵列当(O.cumana Wallr.)和瓜列当(O.aegyptiaca Pers.)的放线菌各1株,分别为淡紫褐链霉菌(Streptomyces enissocaesilis Sveshnikova)和密旋链霉菌(Streptomyces pactum Bhuyan B.K)。其中,密旋链霉菌的菌剂在田间试验中既降低了瓜列当的出土数量又增加了番茄的产量。总之,微生物是防除根寄生杂草列当的一条有效途径。     

Application of plant growth-promoting endophytes (PGPE) isolated from Solanum nigrum L. for phytoextraction of Cd-polluted soils

Many plant growth-promoting endophytes (PGPE) can assist their host plants cope with contaminant-induced stress responses, which can improve plant growth. In this study, four heavy metals resistant endophytic bacteria, Serratia nematodiphila LRE07, Enterobacter aerogenes LRE17, Enterobacter sp. LSE04 and Acinetobacter sp. LSE06, were isolated from Cd-hyperaccumulator Solanum nigrum L. grown in metal-polluted soil. Their plant growth promoting properties such as production of 1-aminocyclopropane-1-carboxylic (ACC) deaminase, indole-3-acetic acid (IAA), siderophores and phosphate solubilizing activity were characterized in vitro. When added to the Cd-amended soils, all of these four bacteria significantly increased Cd extraction from the soils. Subsequently, a pot experiment was conducted to elucidate the effects of inoculating of these PGPE on the plant growth and Cd uptake by S. nigrum L. grown in three different levels of Cd-contaminated soils. Results showed that the inoculation with these PGPE not only stimulated the growth of host plant, but also influenced the accumulation of Cd in the root, stem and leaf tissue of S. nigrum L. All four strains could colonize the rhizosphere soil and even some can be found in plant interior tissues. The present observations demonstrated that PGPE were valuable microorganism resource which can be exploited to improve the efficiency of phytoextraction.     

Can endophytic Arthrobotrys oligospora modulate accumulation of defence related biomolecules and induced systemic resistance in tomato (Lycopersicon esculentum Mill.) against root knot disease caused by Meloidogyne incognita

The soil community is an often ignored part of research which links plant biodiversity and ecosystem functioning despite their influence on numerous functions such as decomposition and nutrient cycling. Few consistent patterns have been detected that link plant and soil community composition; however, it has not been studied in details. Arthrobotrys oligospora, a model predacious fungus for nematode trapping, beside biocontrol potential may modulate plant health and increase natural antioxidants in tomato fruit directly or indirectly. In the present study we have investigated the effects of nematode trapping fungus A. oligospora on induction and bioaccumulation of natural antioxidant and defence related biomolecules in tomato plants when challenged with Meloidogyne incognita causing root knot. Endophytic and rhizospheric isolates of A. oligospora were isolated from different parts of India and characterized under controlled laboratory conditions. The study describes the multifarious effects of endophytic and rhizospheric isolates of A. oligospora in green house and field conditions in tomato plants when inoculated individually or in combination. It was found that A. oligospora EAO-147 and RST-101 when applied individually or in combination significantly increased various attributes in plants. Among both the isolates, endophytic A. oligospora EAO-147 was found to be more potential in enhancing the defence related biomolecules, enzymes and exhibited biocontrol potentials against M. incognita. With application of A. oligospora, increase in nutritional quality of ripe tomato fruits (mineral nutrients and natural antioxidant properties) was also demonstrated first time. Results suggest that application of A. oligospora, particularly endophytic, not only helps in control of nematodes but also increase plant growth as well as enhances the nutritional value of tomato fruits. Thus, it proves to be an excellent biocontrol as well as plant growth promoting agent.     

西瓜根际促生菌筛选及生物育苗基质研制

通过从西瓜根际分离筛选具根际定殖能力的植物根际促生菌,将其保活添加至普通育苗基质研制生物育苗基质,以确保功能菌株能够在苗期定殖根际,进而在移栽后发挥促生功能。结果表明,分离获得一株同时具有产吲哚乙酸(IAA)和NH_3,且对尖孢镰刀菌和茄科劳尔氏菌均有拮抗作用的植物根际促生菌(PGPR)菌株N23;在三季育苗试验中,与普通基质处理(CK)相比,添加菌株N23的生物育苗基质所育种苗,在多项苗期生长指标上均表现出稳定的促生作用;盆栽试验表明,除叶绿素相对含量测量值(SPAD)外,生物基质所育西瓜种苗的其他检测指标均显著高于对照(普通育苗基质所育种苗,下同);田间试验表明,生物基质所育种苗西瓜、黄瓜、辣椒和番茄种苗移苗后,在苗期植株株高和茎粗均显著优于对照,在产量上均增产10%以上。结合形态、生理生化特征和16S rDNA基因序列分析,初步鉴定菌株N23为芽孢杆菌属细菌(Bacillus sp.)。综上,利用芽孢杆菌N23研制的生物育苗基质能够有效促进所育不同作物种苗质量,增强移栽后作物的生长和田间产量。因此,本研究能够为根际有益微生物的应用提供新的思路,为生物育苗基质的研制提供理论支撑。     

Screening of rhizobacteria isolated from maize (Zea mays L.) in Rio Grande do Sul State (South Brazil) and analysis of their potential to improve plant growth

Plant growth-promoting rhizobacteria (PGPR) are considered to have a beneficial effect on host plants and may facilitate plant growth by different mechanisms. In this work, the influence of different soil types on the bacterial diversity and the stimulatory effects of selected PGPR on two cultivars of maize were investigated. A set of 292 strains was isolated from the roots and rhizosphere soil of maize cultivated in five different areas of the Rio Grande do Sul State in Brazil. 16S rDNA-PCR-RFLP and 16S rDNA partial sequencing were used for identification, and the Shannon–Weaver index was used to evaluate bacterial diversity. We evaluated the ability of each isolate to produce indole acetic acid (IAA), siderophores and solubilize phosphates. On the basis of multiple PGP traits, six isolates were selected to test their potential as plant growth-promoting rhizobacteria on maize plants. In both the roots and the rhizospheric soil of maize, the dominant bacterial genera identified were Klebsiella and Burkholderia. IAA producers were distributed widely among isolates, regardless of the sampling site. Approximately 42% of the isolates exhibited at least two attributes, and 24% showed all three PGP traits. Three strains, identified as Achromobacter, Burkholderia, and Arthrobacter, were effective as PGPR in both of the cultivars evaluated.     

Non-streptomycete actinomycetes as biocontrol agents of soil-borne fungal plant pathogens and as plant growth promoters

Among soil microorganisms, bacteria and fungi and to a lesser extent actinomycetes, have received considerable attention as biocontrol agents of soil-borne fungal plant pathogens and as plant growth promoters. Within actinomycetes, Streptomyces spp. have been investigated predominantly, mainly because of their dominance on, and the ease of isolation from, dilution plates and because of the commercial interest shown on the antibiotics produced by certain Streptomyces spp. Many of non-streptomycete actinomycetes (NSA) taxa are therefore rarely reported in literature dealing with routine isolations of biocontrol agents and/or plant growth promoters from plant and soil. It is clear that special isolation methods need to be employed in routine isolations to selectively isolate NSA. Some interesting information exists, albeit in relatively few reports compared to that on other microorganisms, on the biological activities of NSA, especially in relation to their mechanisms of action in the biological control of soil-borne fungal plant pathogens and plant growth promotion. This review presents an overview of this information and seeks to encourage further investigations into what may be considered a relatively unexplored area of research. Certain soil environmental factors, especially in horticultural systems, could be manipulated to render the soil conducive for the biological activities of NSA. A variety of NSA isolated by selective methods have not only shown to be rhizosphere competent but also adapted for an endophytic life in root cortices. Some of the NSA, including endophytic strains that have shown potential to suppress soil-borne fungal plant pathogens, are able to employ one or more mechanisms of antagonism including antibiosis, hyperparasitism and the production of cell-wall degrading enzymes. Strains of NSA promote plant growth by producing plant growth regulators. Enhancement of plant growth by the antagonists are considered to help the host by producing compensatory roots that mask the impact of root diseases.     

Fungal endophyte Penicillium janthinellum LK5 can reduce cadmium toxicity in Solanum lycopersicum (Sitiens and Rhe)

We investigated the role of gibberellins-producing endophyte Penicillium janthinellum LK5 associated with Solanum lycopersicum (host), abscisic acid (ABA)-deficient tomato mutant Sitiens and its wild-type Rheinlands Ruhm (Rhe) plants under cadmium (Cd) stress. A 100-μM Cd application to host, Sitiens and Rhe reduced the shoot growth, chlorophyll content and stomatal conductance. However, these parameters were significantly (P?<?0.0011) higher (1.0- to 2.6-folds) in host, Sitiens and Rhe under endophytic association than in non-endophyte infected plants (control) under Cd stress. Furthermore, endophytic association minimized the Cd-induced membrane injury and oxidative stress to host, Sitiens and Rhe plants by reducing electrolytes and lipid peroxidation while increasing the content of reduced glutathione and catalase activities as compared to non-endophyte-infected plants. Stress-responsive ABA content significantly increased (～2-folds) in Sitiens and Rhe under endophyte association, while in host plants it was decreased under Cd stress. Salicylic acid content was ～?1.7-fold higher in host, Sitiens and Rhe plants under Cd stress and endophyte association than in the control. Besides gibberellins production, the endophyte has the potential to solubilize phosphates (12.73?±?0.24 mg/l) since higher P was observed in the roots of Sitiens, Rhe and host plants. Similarly, nutrients like sulfur and calcium were more efficiently assimilated in roots of endophyte-associated plants than control under Cd stress. Conversely, Cd accumulation was significantly decreased (P?<?0.001) in the roots of endophyte-inoculated host, Sitiens and Rhe than control. In conclusion, endophyte symbiosis can counteract heavy metal stress which can exert negative effects on plant growth.     

Changes in the species composition of the rhizosphere and phyllosphere of sugar beet under the impact of biological preparations based on endophytic bacteria and their metabolites

The species structure of the mycobiota in the rhizosphere and phyllosphere of sugar beet in ontogenesis was studied. The treatment of the plants with biopreparations based on endophytic bacteria and their metabolites (Phytosporin-M, Vitaplan, and Albit) were shown to create conditions for the colonization of the plant rhizosphere and phyllosphere by bacteria–antagonists displacing phytopathogenic microorganisms and stimulating plant growth, which induces the transformation of the microbial cenosis.     

Promotion of plant growth by phytohormone-producing endophytic microbes of sugar beet

Three plant-growth-promoting isolates of endophytic bacteria from sugar beet roots produced indole-3-acetic acid (IAA) in vitro in a chemically defined medium. The three isolates were selected from 221 endophytic bacteria isolated from surface-disinfected beet roots and evaluated for potential to produce IAA and to promote beet growth under gnotobiotic and glasshouse conditions. The inoculation of roots of beet by three selected bacteria isolates significantly increased plant height fresh and dry weights and number of leaves per plant, as well as levels (p < 0.01) of phytormones compared with control plants. In the glasshouse test, the three selected bacterial isolates were recovered from inside roots in all samplings, up to 8 weeks after inoculation, indicating that the roots of healthy beet may be a habitat for these endophytic bacteria.