根瘤菌竞争结瘤的研究进展

根瘤菌竞争结瘤的研究进展樊妙姬,马庆生（广西农业大学生物技术教研室,南宁５３０００５）根瘤菌剂接种豆科作物是一项普遍推广的农业技术。但由于土壤中含有固氮效率差别极大的土著根瘤菌群体,于扰和降低了接种根瘤菌的占瘤率,致使接种根瘤菌剂的增产效果不显著,［...     

根瘤菌的结瘤基因与结瘤因子

根瘤菌的结瘤基因与结瘤因子郭先武（华中农业大学农业部农业微生物重点实验室武汉４３００７０）根瘤菌侵染豆科植物形成根瘤,并合成ＮＨ３供植物利用,其自身也在植物环境中得以有效延续。这就是根瘤菌与宿主植物的共生关系。形成共生关系的基因分成三类［７］,一类是...     

根瘤菌结瘤因子的研究进展

根瘤菌结瘤因子的研究进展靖元孝（华南师范大学生物系,广州５１０６３１）关键词根瘤菌结瘤因子Ｒｈｉｚｏｂｉｕｍ、Ｂｒａｄｙｒｈｉｚｏｂｉｕｍ和Ａｚｏｒｈｉ－ｚｏｂｉｕｍ三类细菌能侵染豆科植物并形成根瘤。在根瘤形成过程中,共生伙伴之间首先进行信号物质交换...     

根瘤菌结瘤因子的结构和功能

结瘤因子是根瘤菌分泌的寡糖,它作为外在信号,诱发宿主植物根部各种生理反应。引起根毛变形,诱导皮层细胞分裂,形成根瘤原基,作者主要就这一早期结瘤过程中结瘤因子的结构和功能作一综述。     

哈茨木霉发酵液中肽类物质对豇豆土著根瘤菌竞争结瘤的影响

通过树脂吸附、离子交换、薄层层析、高效液相色谱系统以及紫外、质谱等分离、纯化和鉴别的方法,从哈茨木霉T2-16菌株发酵液中分离得到一种对豆科作物生长具促进作用的肽类物质。用该肽类物质对豇豆土著根瘤菌进行处理后,用AFLP技术研究了该物质对供试根瘤菌遗传稳定性和在土壤中竞争结瘤能力的影响。结果表明,传代次数和培养温度(28℃~36℃范围)对供试根瘤菌的遗传性状无明显影响,其AFLP指纹未发生明显变化;但经木霉肽类代谢产物处理后,根瘤菌竞争结瘤能力得到提高,为对照根瘤菌的1.53倍。     

紫云英根瘤菌结瘤因子的初步研究

最近的研究结果表明,豆科植物与根瘤菌的共生识别是一种双向的信号物质交换过程.首先是豆科植物的根或种子分泌类黄酮物质,诱导根瘤菌的结瘤基因(nod genes)产生结瘤因子(nod factors),分泌到胞外,为植物所接受,从而引发植物某些基因表达,细胞分化,细胞壁形成,最终导致根毛变形等一系列变化.已经测定了几种苜蓿根瘤菌(Rhizobium meliloti)和豌豆根瘤菌(R.leguminosarum bv.viciae)结瘤因子的分子结构式,它们均属于寡糖胺类物质,在没有根瘤菌存在的条件下,结瘤因子能独立地促使根毛发生变形,这是检测结瘤因子是否存在的重要手段,即根毛变形试验(Root hairdeformation assay,简称Had试验).高浓度的结瘤因子甚至能诱导植物产生空瘤,其组织结构与典型的根瘤相同.     

紫云英根瘤菌结瘤基因的定位研究

以根瘤菌nod ABC基因的结构同源性为依据,对紫云英根瘸菌结瘤基因(nod)进行了定位。结果表明,紫云英根瘤菌菌株7653R的nod基因同时存在于小质粒pR37653Ra和大质粒pRa7653Rb上;S52的nod基因位于小质粒pRa52a上;SR72的nod基因单拷贝位于小质粒pRa72a上,含有部分nod ABC基因的BamHI、HiadIII和Pstl酶切片段分别为22.4kb、11．9kb和2．2kb,EcoRl酶切片段为4．6kb和3．0kb;HR104的nod基因也是单拷贝,仅存在于小质粒PRal04a中,含有部分nod ABC基因的 BaraHI、EcoRL和Pstl酶切片段分别为 22．4kb、9．1kb和2．2kb。     

大豆基因工程根瘤菌田间结瘤和共生固氮效应

利用三亲本接合转移方法,将快生型大豆根病菌B_(52)的基因文库克隆转移到受体菌慢生型大豆根瘤菌2210中,获得4株大豆基因工程根瘤菌(32.43、B—2—6、B—3—8)。田间接种试验表明:在大豆分枝期(V2),43和32结瘤效分别比不接种对照增加117.9％和100.4％;在初花期(R_1),32和B—2—6结瘤数分别比对照增加122.5％和91.6％,根瘤固氮酶活性增加233.3％和195.6％;在结荚始期(R3),B—2—6和32结瘤数比对照增加78.5％和70.1％,根瘤固氟酶活性43和B—2—6分别比对照增加53.4％和49.3％。产量统计表明:32、B—2—6和43比对照分别增产16.8％、14.3％和12.2％,亩增收大豆分别为28.2、24.1和20.6公斤。以上三个菌株均比受体菌株2210增产率高。     

Performance of chickpea,lentil and lupin nodulated with indigenous or inoculated rhizobia micropartners under nitrogen,boron, cobalt and molybdenum fertilization schedules

Chickpea (Cicer arietinum), lentil (Lens esculenta) and lupin (Lupinus albus) responded to inoculation with their respective symbiotants:Rhizobium loti, Rhizobium leguminosarum biovarviceae andBradyrhizobium sp. (Lupinus) alone or with (NH₄)₂SO₄ at 30 ppm N. Soil application of Na₂MoO₄.2H₂O at 3 ppm Mo, CoCl₂.6H₂O at 2 ppm Co²⁺ or Na₂B₄O₇.10H₂O at 1 ppm B with 0 and 30 ppm N increased nodule weight and plant dry weight and N-content 60 days after sowing and seed yield, seed size and the N and P contents of seed. Nodule numbers slightly decreased with application of such chemicals. Mo enhanced performance of the three plants more than Co and B. Yield, total N and P-contents of lupin were comparable with those of chickpea or lentil and lupin had the highest levels of both N₂-fixation and N absorption from the fertilizer. IndigenousR. leguminosarum biovarviceae was more established in the soil compared with the other two, chickpea and lupin, micropartners.     

Nodulation and nitrogen fixation in extreme environments

Biological nitrogen fixation is a phenomenon occurring in all known ecosystems. Symbiotic nitrogen fixation is dependent on the host plant genotype, theRhizobium strain, and the interaction of these symbionts with the pedoclimatic factors and the environmental conditions. Extremes of pH affect nodulation by reducing the colonization of soil and the legume rhizosphere by rhizobia. Highly acidic soils (pH<4.0) frequently have low levels of phosphorus, calcium, and molybdenum and high concentrations of aluminium and manganese which are often toxic for both partners; nodulation is more affected than host-plant growth and nitrogen fixation. Highly alkaline soils (pH>8.0) tend to be high in sodium chloride, bicarbonate, and borate, and are often associated with high salinity which reduce nitrogen fixation. Nodulation and N-fixation are observed under a wide range of temperatures with optima between 20–30°C. Elevated temperatures may delay nodule initiation and development, and interfere with nodule structure and functioning in temperate Iegumes, whereas in tropical legumes nitrogen fixation efficiency is mainly affected. Furthermore, temperature changes affect the competitive ability ofRhizobium strains. Low temperatures reduce nodule formation and nitrogen fixation in temperate legumes; however, in the extreme environment of the high arctic, native legumes can nodulate and fix nitrogen at rates comparable to those observed with legumes in temperate climates, indicating that both the plants and their rhizobia have successfully adapted to arctic conditions. In addition to low temperatures, arctic legumes are exposed to a short growing season, a long photoperiod, low precipitation and low soil nitrogen levels. In this review, we present results on a number of structural and physiological characteristics which allow arctic legumes to function in extreme environments.     

Nodulation and biological nitrogen fixation of 80 soybean cultivars in symbiosis with indigenous rhizobia

Eighty soybean cultivars were assessed for their potential for nodulation and nitrogen fixation with indigenous rhizobia in a Nigerian soil. Seventy-six days after planting (DAP) 87%, 3% and 10% of the soybean cultivars had from 0 to 30, 31 to 60 and over 61 nodules/plant, respectively. Only 8% had a nodule dry weight of 600 to 1100 mg/plant. At 84 DAP the proportion of nitrogen derived from the atmosphere (Ndfa) ranged from 0 to 65% 16% of the cultivars derived 51 to 65% of their N₂ from the atmosphere. The diversity of soybean germplasm and the variation in nodulation and N₂ fixation permitted the selection of the five best cultivars in terms of their compatibility with indigenous rhizobia, % Ndfa and the amount of N₂ which they fixed.     

斜茎黄芪根瘤菌结瘤基因nodA PCR扩增及PCR-RFLP分析

对采自我国北方地区的16株斜茎黄芪根瘤菌代表菌株的共同结瘤基因nodA进行了PCR扩增及PCR-RFLP分析研究。来自Mesorhizobium和Rhizobium系统发育分支的代表菌株都得到了nodA PCR扩增产物;而来自Agrobacterium系统发育分支的代表菌株都没有得到nodA PCR扩增产物。进一步的nodAPCR-RFLP分析结果表明斜茎黄芪根瘤菌具有很大的nodA基因遗传多样性,具有4种不同的16S rDNAPCR-RFLP遗传图谱类型的12株斜茎黄芪根瘤菌具有8种不同的nodA PCR-RFLP遗传图谱类型。但是斜茎黄芪根瘤菌nodA基因遗传多样性随种群而变化,来自M.septentrionale的具有相同的16S rDNA PCR-RFLP遗传图谱类型的4个代表菌株具有4种不同的nodA PCR-RFLP遗传图谱类型;而来自M.tempera-tum的具有相同的16S rDNA PCR-RFLP遗传图谱类型3个代表菌株则具有相同的nodA PCR-RFLP遗传图谱类型。此外,来自不同种的具有不同16S rDNA PCR-RFLP遗传图谱类型的菌株却具有相同的nodA PCR-RFLP遗传图谱类型,说明nodA基因可能在根瘤菌的不同种间发生了水平转移。     

Compatibility and Coselection of Vesicular-Arbuscular Mycorrhizal Fungi and Rhizobia for Tropical Legumes

Abstract

The effect of dual inoculation on three local cultivars (Miss Kelly, Portland Red, Round Red) of red kidney bean (Phaseolus vulgaris, L.) with four strains of Rhizobium phaseoli (B36, B17, T2, and CIAT652) and three species of vesicular-arbuscular mycorrhizal (VAM) fungi (Glomus pallidum, Glomus aggregatum, and Sclerocystis microcarpa) was examined in sterilized and nonsterilized soil. Symbiotic efficiency (improved plant growth response and enhanced nitrogen (N) and phosphorus (P) nutrition) was dependent on the particular combination of Rhizobium strain, VAM fungus, and cultivar of kidney bean. Whereas rhizobial strains B36 and B17 paired with G. pallidum or G. aggregatum showed increased growth response of cv. Miss Kelly and Portland Red, rhizobial strain T2 paired with any of the three VAM fungi was the best compatible pairing for the cv. Round Red. It is suggested that even though dual inoculation significantly improves the growth response of the bean, the best pairings of VAM fungus and rhizobia for legumes is a question to be carefully examined.     

Number of Rhizobia and delayed inoculation influence nodulation of clovers

The relationship between numbers of rhizobia and nodulation response of legumes is of considerable practical importance. Experiments were done under controlled conditions to determine the influence of numbers of Rhizobium leguminosarum biovar. trifolii on nodulation of arrowleaf clover (Trifolium vesiculosum Savi.) and crimson clover (T. incarnatum L.). Numbers of rhizobia in excess of 1000 per seed did not substantially increase earliness of nodulation or total number of nodules formed on the taproot. Nodules, however, were formed nearer the top of the taproot as numbers of rhizobia increased to 100,000 per seed. Delayed inoculation experiments indicated that nodulation sites for these clovers only remained susceptible to infection for less than 1 day. Delaying inoculation for 4 days resulted in only a 1 to 2 day delay in nodulation for arrowleaf and crimson clovers respectively and no delay for subterranean clover (T. subterraneum L.). Apparently, larger seedlings nodulated faster.     

寄主大豆对根结瘤的控制

我国９个大豆（ＧｌｙｃｉｎｅｍａｘＬ．Ｍｅｒｒ．）品种感染根瘤菌ＵＳＤＡ１１０后,产生不同的结瘤数,低者在２０个以下．高者在６０个以上。赤豆、绿赤豆也可被感染结瘤,而豇豆、扁豆则不能。超结瘤大豆ｎｔｓ３８２作为接穗时能诱导我国大豆原结瘤数有４５个的开育１０号、原结瘤数有１２个的大黄分别发生高结瘤。ｎｔｓ３８２作为砧木时,则不能表现超结瘤．表明超结瘤因子能传给我国大豆,反之存在于我国大豆中的限制超结瘤的因子也能传给ｎｔｓ３８２。ｎｔｓ３８２于ＮＯ３－环境中仍表现超结瘤的特点也能导入开育１０号、大黄及赤豆根部,并使之在ＮＯ３－环境中结瘤。在ＮＯ３－环境中不能结瘤的开育１０号作为接穗,ｎｔｓ３８２作为砧木的嫁接植株,于子叶生长阶段接受ＮＯ３－时,仍能结瘤,于真对生长时接受ＮＯ３－时．则不能结瘤,表明限制结瘤因子于真叶细胞中被诱导形成。     

草木樨属根瘤菌的16S rDNA-RFLP分析

采用16S rDNA-RFLP分析方法对草木樨属根瘤菌进行了遗传多样性及系统分类研究。结果表明,3种限制性内切酶(HaeⅢ、HinfⅠ、MspⅠ)对所有供试菌株的酶切图谱类型组合只有2种。类型I的代表菌株CC-NWSX0003-1与豌豆根瘤菌(R.leguminosarum)的模式菌株USDA2370的序列相似性达到99.8%,在分类地位上属于根瘤菌属(Rhizobium)分支;类型Ⅱ的代表菌株CCNWGS0006与草木樨中华根瘤菌(Sinorhizobium meliloti)的16S rDNA相似性为100%,属于中华根瘤菌属(Sinorhizobium)分支。     

内蒙古乌拉尔甘草根瘤菌的遗传多样性分析

从内蒙古乌拉尔甘草根瘤中共分离到54株具有根瘤菌属特征的菌株。采用ERIC-PCR分析方法,发现这些菌株存在特异的扩增条带,能够分辨出从不同年份植株上分离菌株的差异。选取有代表性的菌株进行回接并对结瘤效果好的菌株进行序列分析,发现R31与Mesorhizobium temperatum(T)AF508208、R50与Meso-rhizobium mediterraneum(T)L38825相似性都为99%,属于中慢生根瘤菌属。