Effect of exudate released from seeds and seedling roots of common bean (Phaseolus vulgaris L.) on proliferation of Rhizobium sp. (Phaseolus)

Effects of seed and root exudates obtained from common bean on the proliferation of Rhizobium sp. (Phaseolus) were examined in a combination of three plant cultivars with three Rhizobium strains. In the first experiment, seed or root exudate was mixed with an Andosol soil extract, and bacterial proliferation in the mixture was traced. Seed exudate was prepared from hydroponic solution used in seed imbibition for 24 h, and a series of root exudates was prepared from a hydroponic solution collected every 24 h from the initiation of rooting up to 96 h after rooting. Regardless of the common bean cultivars and Rhizobium strains used, Rhizobium population markedly increased of the 24 h of culture in the mixture containing seed exudates, whereas a negligible increase was detected in the mixture with root exudates. The mixture containing root exudates collected within a period of 72–96 h after initial rooting (96–120 h after seed imbibition) exerted an inhibitory effect on Rhizobium proliferation. The seed exudates contained large amounts of sugars, amino acids, nitrogen, phosphorus, potassium, and magnesium compared to any root exudates. In the second experiment, Rhizobium was inoculated directly to common bean seeds sowed in a vermiculite bed which was sterilized and moistened with a plant nutrient solution. Compared with the control (without seed), a remarkable increase in the number of bacterial cells was observed in all the combinations of plant cultivars and Rhizobium strains 24 h after sowing. These results reveal that seed exudates of common bean have a substantial potential to promote Rhizobium proliferation, and that root exudates in a particular period of culture contain some inhibitory factors.     

Root exudates as pre-invasive factors in the modulation of chick pea varieties

Five chick pea (Cicer arietinum L.) varieties when inoculated with an effective Rhizobium strain showed significant variations in nodule number. The root exudates of the plant varieties were analysed for sugars, TCA cycle intermediates and amino acids. Xylose, citrate, alanine and phenylalanine were detected in exudates of one or two varieties, in addition to compounds common to all varieties such as glucose, glucosamine, ribose, serine, homoserine and glutamic acid. However, the concentration of all these compounds in the exudates collectively was inadequate to support Rhizobium growth under aseptic conditions. Several of the exuded compounds were chemotactic at very low concentrations. The rhizobia showed taxes toward growing roots of all the varieties in agar plates. Competition experiments showed that the rhizobia have a multiple-chemotactic system like that of Escherichia coli. It appears that root exudates accumulate Rhizobium along the growing roots through chemotaxis. The minor differences in exudate composition among varieties is not a factor responsible for variation in nodule number.     

Effect of soil pH on plant growth and nodulation of cowpea

Abstract

A study was conducted to evaluate the effect of soil pH on rhizobium inoculation, plant growth and nodulation of cowpea (Vigna unguiculata). Both inoculated and non‐inoculated seeds of the cultivar ‘California Blackeye No. 5’ were grown in the greenhouse in plastic pots with growth medium being a Norfolk sandy loam (Fine, loamy siliceous, thermic, Typic Palendult) soil under different pH levels. Both soil pH and rhizobium inoculation significantly affected root length, plant height, nodule and pod number per plant. Within the pH range of 6.6 to 7.6, these growth parameters generally were at their maximum, decreasing above or below this pH range. Non‐inoculated plants produced some nodules, indicating failure of the methyl bromide to totally destroy all residual soil rhizobta before inoculation treatment.

The inoculated plants produced more seeds and the increased number of nodules of treated plants was directly related to increased seed weight. Since nodule number was highest at the approximate pH range of 6.6 to 7.6, this range was considered optimum for nodulation of cowpea by this strain of rhizobium under greenhouse conditions. At pH 7.5 and above, roots tended to be more fibrous and nodules were generally smaller in size.     

氮素对不同大豆品种根系分泌物中有机酸的影响

采用室内溶液培养方法,分别研究了接种根瘤菌处理下,两种氮源和两种氮浓度对两个大豆品种根系分泌物中有机酸的影响。结果表明,合丰25号根系分泌的有机酸种类和数量无论苗期或花期,接种或不接种根瘤菌,均表现为硝态氮处理高于酰胺态氮处理,表明合丰25号大豆更喜硝态氮,硝态氮促进了有机酸的分泌。绥农10号在酰胺态氮下的有机酸种类和数量均高于硝态氮处理,表明其更喜酰胺态氮,酰胺态氮下根瘤菌的存在增加其根系分泌物中有机酸种类和数量。可见,大豆根系分泌物中有机酸的种类和数量因品种而异,因品种对氮源的喜好而变化;根瘤菌在不同程度上增强或减弱根系有机酸的分泌作用。柠檬酸受氮素供应浓度影响很大,当氮素供应浓度较低时,大豆根系分泌物中可检测到柠檬酸,供氮浓度升高则检测不到。     

新开垦土壤上构建玉米/蚕豆-根瘤菌高效固氮模式

为了在新开垦土壤上构建高效种植模式,本文采用温室盆栽和大田试验相结合的方法,选用4种根瘤菌接种方式(保水剂拌种、清水拌种、三叶期灌根和种子丸衣化)接种4种不同蚕豆根瘤菌(NM353、CCBAU、G254和QH258),分析接菌后新开垦土壤上玉米/蚕豆间作体系的生产潜力、地上部氮素吸收和结瘤特性以及生物固氮等方面的优势,拟为该体系筛选出高效的根瘤菌及其接种技术。结果表明:接种NM353后,玉米/蚕豆间作体系中蚕豆籽粒产量比单作平均增加152.84%,而玉米保持相对稳产;以保水剂拌种的方式接种NM353的间作蚕豆地上部氮素积累量最高,蚕豆结瘤数、瘤重、固氮比例和固氮量均高于本试验中其他3种方式接种的根瘤菌。在盛花期和盛花鼓粒期,接种NM353蚕豆的固氮比例比接种CCBAU的分别高19.1%和11.1%,在各个生育时期两者固氮量之间差异均达显著水平;接种NM353与接种其他菌种间固氮量和固氮比例差异更显著。因此,在新开垦土壤上,用保水剂拌种的方式对间作蚕豆接种NM353根瘤菌,构建玉米/蚕豆-根瘤菌高效固氮体系,为新开垦土壤合理开发利用的可持续发展模式。     

大豆/玉米间作体系中接种AM真菌和根瘤菌对氮素吸收的促进作用

利用大豆和玉米之间根系不同分隔方式的盆栽试验,研究了在玉米/大豆间作体系中接种大豆根瘤菌、AM真菌Glomus mosseae和双接种对间作体系氮素吸收的促进作用。结果表明,双接种处理显著提高了大豆及与其间作玉米的生物量、氮含量,双接种大豆/玉米间作体系总吸氮量比单接AM菌根、根瘤菌和不接种对照平均分别增加22.6%、24.0%和54.9%。大豆促进了与其间作玉米对氮素的吸收作用,在接种AM真菌和双接种条件,间作玉米的AM真菌侵染率提高,大豆根瘤数增加; 接种AM真菌处理,不分隔和尼龙网分隔比完全分隔玉米吸氮量的净增加量是未接种对照的1.8、2.6倍,双接种处理分别是对照的1.3和1.7倍。说明在间作体系中进行有效的根瘤菌和AM真菌接种,发挥两者的协同作用对提高间作体系土壤养分利用效率,进一步提高间作体系的生产力有重要的意义。     

接种耐酸根瘤菌和施钙对酸性土上紫花苜蓿生长的影响

采用裂区设计法研究了重庆缙云山酸性土上施钙与接种耐酸根瘤菌对紫花苜蓿生长和品质的影响。结果发现:接种耐酸苜蓿根瘤菌对苜蓿植株瘤重、根鲜重、株高、植株上部鲜重、全氮含量和酸性土壤中根瘤菌数量的提高影响显著;施Ca2+ 5 mmol/L与10 mmol/L处理与不施Ca2+处理相比,能显著增加植株根鲜重、株高和地上部鲜重,也能显著增加瘤重;瘤重与植株地上部鲜重、根鲜重和株高呈极显著相关关系,与植株全氮含量呈显著相关关系,说明良好的结瘤性能能够提高酸性土上紫花苜蓿的产量和品质。     

Azospirillum brasilense Az39 and Bradyrhizobium japonicum E109, inoculated singly or in combination,promote seed germination and early seedling growth in corn (Zea mays L.) and soybean (Glycine max L.)

Inoculants are biological formulations that combine a stable microorganism population and various types of compounds produced and released during fermentation, such as phytohormones and plant growth regulators. Azospirillum brasilense strain Az39 and Brayrhizobium japonicum strain E109 were previously shown to produce indole 3-acetic acid (IAA), gibberellic acid (GA₃) and zeatin (Z). We tested the hypothesis that such compounds are responsible for early growth promotion in inoculated corn (Zea mays L.) and soybean (Glycine max L.) seedlings. Seeds were inoculated with Az39, E109, or both, and kept in a chamber at 20–30 °C under a controlled photoperiod to evaluate seed germination. To evaluate root and shoot length and dry weight, and number of nodules and percentage of nodulated seedlings, in soybean, seedlings were kept in a growth chamber for 14 days under similar photoperiod and temperature conditions. Az39 and E109, singly or in combination, showed the capacity to promote seed germination, nodule formation, and early development of corn and soybean seedlings. Both strains were able to excrete IAA, GA₃ and Z into the culture medium, at a concentration sufficient to produce morphological and physiological changes in young seed tissues.     

Responses of Root Growth and Nitrogen Transfer Metabolism to Uniconazole,a Growth Retardant,during the Seedling Stage of Soybean under Relay Strip Intercropping System

Relay strip intercropping of soybean has been widely developed in the southwest of China to secure China's soybean production. However, due to the shading from maize, soybean plants are thin and have a poor root system. Uniconazole is a plant-growth retardant that could enhance root vigor; increase root length, root volume, and root dry weight; and affect nitrogen (N) metabolism. To understand the effects of uniconazole on the root growth and N-transfer metabolism of soybean seedlings under relay strip intercropping, the changes in some morphological characteristics of root, dry-matter weight, root vigor, nitrate (NO₃ ^?)-N, ammonium (NH₄ ⁺)-N, and amino acid of xylem sap after seed treatment with uniconazole powder (0, 2, 4, and 8 mg kg^?1 seed) were investigated. Main root length, total lateral root lengths, first lateral root numbers, root nodule numbers, root vigor together with bleeding sap, bleeding sap–top ratio, root dry weight, and root/shoot ratio were increased, indicating uniconazole improved soybean root system in relay strip intercropping. Uniconazole powder treatment could increase NO₃ ^?-N, NH₄ ⁺-N, and total amino acid of xylem sap, to increase the potential of leaf and root N reduction and assimilation, and increase of leaf and root N contents. Thus, results suggested that uniconazole treatment can improve root growth and N transfer mechanism of soybean to support its further growth.     

大豆根分泌物活化难溶性铝磷的研究

在酸性红壤上，土壤有效磷含量低，大部分磷以难溶性磷形式存在，这是影响作物生产的重要限制因素之一。作物根分泌物活化难溶性磷的能力对改善其磷素营养具有重要意义。本文系统研究了大豆根分泌物对难溶性铝磷的活化效果，同时运用阴、阳离子交换树脂将根分泌物分成阴离子组分、中性组分和阳离子组分，活化结果表明．阴离子组分对铝磷的活化量显著高于中性组分和阳离子组分。运用分子膜把根分泌物分成大于8K、8～3．5K、3．5～1K和小于1K组分．发现对铝磷活化量最大的组分为小于1K根分泌物组分。另外．小于1K阴离子组分对铝磷的活化量为缺磷13．2mg／pot，供磷可达9．3mg／pot，分别占总根分泌物活化量的71％和57％。运用离子色谱仪对小于1K阴离子组分根分泌物测定表明，供磷和缺磷处理．根系均能分泌少量的柠檬酸和苹果酸，约占铝处理的10％～20％，但处理之间差异不显著。上述研究表明．除有机酸影响难溶性铝磷活化之外，根分泌物中可能还存在其它物质对铝磷活化有促进作用，相关研究正在深入进行之中。     

Response of Soybean (Glycine max (L.) Merr) to PS-Foundation 1-0-1 Biostimulant,Triple Super Phosphate,and Rhizobium Inoculant

ABSTRACT

Soybean yields in Ghana are low and stagnant in spite of the trio of recommendations: (1) improved seed, (2) rhizobium inoculant and (3) phosphorous fertilizer application being promoted by government to boost productivity. This study evaluates the response of soybean to Pro-soil biostimulant, triple super phosphate (TSP), and rhizobium inoculant in the interior savanna of Ghana. A treatment structure comprising two mainplot factors (biostimulant and conventional), and four subplots factors; TSP, inoculant, TSP+Inoculant and unamended control arranged in a split-plot design was used for this study. Apart from dry matter which increased by 42%, Pro-soil biostimulant as a stand-alone management practice did not significantly increase agronomic parameters measured in this study. Biostimulant did not have a significant effect on grain yield, nodule weight, nodule number, canopy diameter, and plant height. Application of TSP alone, and in combination with inoculant, significantly increased yield, plant dry matter, nodule weight, nodule number, and dry pod weight. Highest soybean yield was obtained from TSP + Inoculant treatment, averaging 3.6 t ha^?1 compared to 1.8 t ha^?1 for control. Biostimulant, TSP+Inoculant combination resulted in yields as high as 4 t ha^?1. Overall, the results indicate that neither PS-Foundation biostimulant nor rhizobia inoculation can be used as stand-alone management practices to increase soybean yield. However, an integrated application of PS-Foundation biostimulant, TSP, and inoculant could double current soybean yields in Ghana.     

接种根瘤菌对蚕豆/玉米间作系统产量及结瘤作用的影响

通过田间试验,研究了不同施氮水平下蚕豆接种根瘤菌GS374对蚕豆/玉米间作系统产量及蚕豆结瘤作用的影响。结果表明,不施氮处理接种根瘤菌所获得的单作或间作系统产量与不接种但施N225kghm-2的相应系统产量相当,且施N225kghm-2处理接种仍能促进蚕豆的结瘤作用。统计分析表明,与不接种根瘤菌、蚕豆单作、不施氮相比,接种、蚕豆/玉米间作、施氮均极显著地提高了蚕豆生物学产量,但只有间作能显著增加其籽粒产量;施氮显著增加玉米生物量和籽粒产量。施N225kghm-2后,蚕豆接种、间作对玉米生物量无显著影响;但不施氮时蚕豆接种显著提高了与之间作的玉米籽粒和生物学产量,增幅分别为34.3%和25.6%。接种根瘤菌显著提高了不同氮处理以籽粒产量为基础计算的土地当量比和不施氮处理以生物学产量为基础计算的土地当量比。蚕豆接种根瘤菌与不接种相比,其单株根瘤数和根瘤干重均显著增加;间作与蚕豆单作相比对根瘤数的影响较小,但显著促进了蚕豆单株根瘤干重的增加。因此,本研究认为豆科作物接种合适的根瘤菌,是进一步提高豆科/禾本科作物间作系统间作优势的又一重要途径。     

大豆根系分泌物中氨基酸对根腐病菌生长的影响

采用砂培和室内模拟方法,研究了两个抗病性不同的大豆品种水溶性根系分泌物中氨基酸组分随作物生长的变化;同时检测了培养基中添加大豆根系分泌物和纯品氨基酸对大豆根腐病菌菌落生长的影响。结果表明,添加大豆苗期和花荚期根分泌物均显著促进尖镰孢菌菌丝生长,添加成熟期根分泌物显著促进腐皮镰孢菌菌丝生长。易感根腐病大豆品种合丰25号花荚期以后根分泌物中氨基酸种类多于抗根腐病大豆品种绥农10号。感病大豆品种根系分泌的氨基酸总量随生育时期增加,在鼓粒期达到最高;抗病大豆品种根系分泌的氨基酸总量在花荚期最高。感病大豆品种根系分泌的主要氨基酸为精氨酸,抗病大豆品种根系分泌的氨基酸主要为天冬氨酸。氨基酸纯品培养中,添加精氨酸和酪氨酸处理的尖镰孢菌菌落直径显著高于不加氨基酸的对照菌落直径;添加丝氨酸和天冬氨酸的处理菌落直径则显著低于对照处理。同时,添加天冬氨酸的培养基上腐皮镰孢菌菌落直径显著低于不加氨基酸的对照。可见,不同大豆品种根系分泌物中氨基酸组分对病原菌生长起着一定的作用,其表现的作用受根际氨基酸种类和氨基酸浓度影响较大,对于不同病原菌的作用存在差异。     

Potential for enhancement of root growth and nodulation of soybean co-inoculated with Azospirillum and Bradyrhizobium in laboratory systems

The potential enhancement of root growth and nodulation in vegetable soybean (AGS190) was studied with application of Azospirillum brasilense (Sp7) and A. lipoferum (CCM3863) co-inoculated with two Bradyrhizobium japonicum strains (TAL102 and UPMR48). Significant root growth stimulation and nodulation were observed in Azospirillum as well as during its co-inoculation with Bradyrhizobium. Nodule formation is linked with the initiation of new roots; nodules were almost absent even in Bradyrhizobium inoculated plant due to the absence of new roots development in clipped rooted seedlings. Total root length, root number, specific root length, root dry matter, root hair development and shoot dry matter were significantly increased by Azospirillum alone and its co-inoculum. Co-inoculated plants significantly influenced the number of nodules and its fresh weight. A. brasilense seemed to perform better in root growth and nodule development compared to A. lipoferum.     

烤烟根系分泌物对烤烟幼苗生长和养分吸收的影响

连作是烟草栽培中的普遍现象,已引起生长抑制、产量下降和品质恶化等问题。本试验采用溶液培养的方法,在培养液中分别加入未分组和分组后的烤烟根系分泌物,研究根系分泌物对烤烟幼苗生长和养分吸收的影响。结果表明,加入未分组的烤烟根系分泌物显著抑制幼苗的生长,降低根系活力,并随加入量的增加抑制作用增强;加入酸溶性、碱溶性、中性组分的根系分泌物,均降低幼苗根系活力,以中性组分的抑制作用较强。三种不同组分的根系分泌物均显著降低根系对NO3-、PO43-、K+离子的吸收,其中中性组分对NO3-吸收的影响最大,而酸溶性组分对K+的吸收抑制作用较强。推测在烤烟根系分泌物中,可能存在多种抑制烤烟生长和养分吸收的化学物质。     

Rhizobium Proliferation-Supporting Substances in Seed Exudates of Common Bean (Phaseolus vulgaris L.)

Seed exudates collected from three cultivars (cv. Hokkaikintoki, Himetebou, and Kurodane-kinugasa) of common bean ( Phaseolus vulgaris L.) were fractionated based on several physicochemical properties, and the nutrient substances in the fractions effective for Rhizobium proliferation were determined. Regardless of the common bean cultivars, the low molecular weight and high polarity fraction showed the most beneficial effect on Rhizobium proliferation. After further separation of the low molecular weight and high polarity fraction, the promoting effect was detected in the non-ionic and the cationic plus ampho-teric subtractions. Although the amount of sugars or amino acids exuded from a seed was, respectively, similar in all the cultivars except for the sugars in Kurodanekinugasa, the content of these compounds per seed-weight was inversely proportional to the seed size. Ten sugars and twenty-one amino acids were, respectively, identified in the non-ionic and cat-ionic plus amphoteric subtractions, and there were some differences in the composition of these substances between common bean cultivars.     

Involvement of programmed cell death in suppression of the number of root nodules formed in soybean induced by Bradyrhizobium infection

Legumes establish symbiosis with nitrogen-fixing rhizobia through root nodules to acquire nitrogen. Legumes control nodule number through systemic (autoregulation of nodulation) as well as local regulation. Moreover, plants defend themselves against bacteria and other pathogens through the induction of localized (localized acquired resistance) and systemic (SAR, systemic acquired resistance; ISR, induced systemic resistance) responses. Herein, we show that the number of root nodules is suppressed by programmed cell death (PCD), and is simultaneously controlled by SAR and ISR in soybean (Glycine max [L.] Merr.). The wild-type soybean cultivar Williams 82 showed markedly fewer root nodule primordia and PCD symptoms, including accelerated DNA degradation, enhanced generation of reactive oxygen species (visualized by 3,3′-diaminobenzidine staining), and excessive cell death (detected on staining with trypan blue) compared to the hypernodulation mutant NOD1-3. These results suggest that PCD suppresses the formation of root nodules in wild-type soybean. In addition, microarray and gene ontology analyses showed that essential components of hypersensitive response (HR) or disease resistance, such as resistance (R) genes, mitogen-activated protein kinase cascade, SAR, salicylic acid, jasmonic acid, ethylene, etc., were activated in wild-type plants. These analyses corroborate the above findings, demonstrating that the suppression of root nodule formation by PCD is accompanied by HR, and is simultaneously controlled by SAR and ISR in soybean. These findings provide new insight into the control of nodulation to balance nutritional requirements and energy status in legumes.     

Abstracts of nippon dojo-hiryogaku zasshi

Seed exudates collected from three cultivars (cv. Hokkaikintoki, Himetebou, and Kurodane-kinugasa) of common bean (Phaseolus vulgaris L.) were fractionated based on several physicochemical properties, and the nutrient substances in the fractions effective for Rhizobium proliferation were determined. Regardless of the common bean cultivars, the low molecular weight and high polarity fraction showed the most beneficial effect on Rhizobium proliferation. After further separation of the low molecular weight and high polarity fraction, the promoting effect was detected in the non-ionic and the cationic plus ampho-teric subtractions. Although the amount of sugars or amino acids exuded from a seed was, respectively, similar in all the cultivars except for the sugars in Kurodanekinugasa, the content of these compounds per seed-weight was inversely proportional to the seed size. Ten sugars and twenty-one amino acids were, respectively, identified in the non-ionic and cat-ionic plus amphoteric subtractions, and there were some differences in the composition of these substances between common bean cultivars.     

Potential of seed and root exudates of the common bean Phaseolus vulgaris L. for immediate induction of rhizobial chemotaxis and nod genes

Abstract

Immediate induction of rhizobial chemotaxis and nod genes by seed and root exudates of the common bean Phaseolus vulgaris L. was investigated. One hour after the onset of Rhizobium incubation in a culture medium composed of common bean exudates and soil extract, a large number of Rhizobium cells were attracted by the seed exudates of all the cultivars (cvs Hokkaikintoki, Himetebou and Kurodanekinugasa), while the media containing root exudates was not statistically different from the control. After 1 h of incubation, the nod genes were induced significantly by the seed exudates of Himetebou and Kurodanekinugasa. In contrast, the seed exudate of Hokkaikintoki and the root exudates of all the cultivars failed to exert a beneficial effect on the immediate induction of the nod genes. These results suggested that the seed exudates displayed a higher potential for immediate induction of rhizobial chemotaxis and nod genes than the root exudates, except for nod gene induction by the seed exudate of Hokkaikintoki.     

4种生物质对大豆双共生系统、土壤微生物及产量的调控

通过田间试验研究施入生物质对根瘤菌、丛枝菌根真菌与大豆双共生系统、土壤微生物及大豆产量的影响。生物质设置秸秆、土豆皮、食用菌废弃料、大豆浸出液4个处理。分别在植株生长第4片复叶展开(V5)、结荚始期(R3)和鼓粒盛期(R6)取样测定。研究结果表明: 外施4种生物质对大豆双共生系统均有不同程度促进作用, 且生物质对大豆菌根形成的促进作用较对根瘤形成的促进更显著, 持续时间更长。在4种生物质中, 秸秆处理表现效果最佳, 不仅对大豆双共生系统、土壤细菌、真菌数量有增效作用, 同时对大豆产量有协同促进作用。在R6期大豆有效根瘤数量、丛枝菌根真菌侵染率、土壤细菌数量分别较对照增加238.46%、26.28%、131.99%, 产量较对照增加69.78%, 且秸秆容易获得, 施用方便, 是有效提高大豆产量的生物质。大豆浸出液处理对大豆双共生系统促进显著, 在R6期有效根瘤数量较对照增加89.74%, 同时丛枝菌根真菌侵染率较对照增加31.23%, 但由于此处理播种前采用浸种方式, 对大豆子叶造成较大损伤, 使保苗率严重降低从而导致产量相对较低。食用菌废弃料和土豆皮处理在3个生育时期对大豆双共生系统的作用不尽一致, 但R6期2个处理的丛枝菌根真菌侵染率和土壤中真菌数量都极显著高于对照。