Enhanced Mineral Uptake by Zea mays and Sorghum bicolor Roots Inoculated with Azospirillum brasilense

Inoculation of corn (Zea mays) seeds with Azospirillum brasilense strain Cd or Sp 7 significantly enhanced (30 to 50% over controls) the uptake of NO₃⁻, K⁺, and H₂PO₄⁻ into 3- to 4-day- and 2-week-old root segments. No gross changes in root morphology were observed; altered cell arrangement in the outer four or five layers of the cortex was seen in photomicrographs of cross sections of inoculated corn roots. The surface activity involved in ion uptake probably increased, as shown by the darker staining by methylene blue of the affected area. Shoot dry weight increased 20 to 30% in inoculated plants after 3 weeks, presumably by enhancement of mineral uptake. Corn and sorghum plants grown to maturity on limiting nutrients in the greenhouse showed improved growth from inoculation approaching that of plants grown on normal nutrient concentrations. Enhanced ion uptake may be a significant factor in the crop yield enhancement reported for Azospirillum inoculation.     

Uptake Hydrogenase (Hup) in Common Bean (Phaseolus vulgaris) Symbioses

Strains of Rhizobium forming nitrogen-fixing symbioses with common bean were systematically examined for the presence of the uptake hydrogenase (hup) structural genes and expression of uptake hydrogenase (Hup) activity. DNA with homology to the hup structural genes of Bradyrhizobium japonicum was present in 100 of 248 strains examined. EcoRI fragments with molecular sizes of approximately 20.0 and 2.2 kb hybridized with an internal SacI fragment, which contains part of both bradyrhizobial hup structural genes. The DNA with homology to the hup genes was located on pSym of one of the bean rhizobia. Hup activity was observed in bean symbioses with 13 of 30 strains containing DNA homologous with the hup structural genes. However, the Hup activity was not sufficient to eliminate hydrogen evolution from the nodules. Varying the host plant with two of the Hup⁺ strains indicated that expression of Hup activity was host regulated, as has been reported with soybean, pea, and cowpea strains.     

Analysis of the Proteome of Common Bean (Phaseolus vulgaris L.) Roots after Inoculation with Rhizobium etli

Proteomics techniques were used to identify the underlying mechanism of the early stage of symbiosis between the common bean (Phaseolus vulgaris L.) and bacteria. Proteins from roots of common beans inoculated with bacteria were separated using two-dimensional polyacrylamide gel electrophoresis and identified using mass spectrometry. From 483 protein spots, 29 plant and 3 bacterial proteins involved in the early stage of symbiosis were identified. Of the 29 plant proteins, the expression of 19 was upregulated and the expression of 10 was downregulated. Upregulated proteins included those involved in protein destination/storage, energy production, and protein synthesis; whereas the downregulated proteins included those involved in metabolism. Many upregulated proteins involved in protein destination/storage were chaperonins and proteasome subunits. These results suggest that defense mechanisms associated with induction of chaperonins and protein degradation regulated by proteasomes occur during the early stage of symbiosis between the common bean and bacteria.     

Variation of Protein among Eleven Varieties of Common Bean (Phaseolus vulgaris)

The acylated, amidated and esterified derivatives of N-acetylglucosaminyl-α(1 → 4)-N-acetylmuramyl tri- and tetrapeptide were synthesized and examined as to their protective effect on pseudomonal infection in the mouse and pyrogenicity in the rabbit. Modifications of the terminal end function of the peptide moieties in their molecules caused enhancement of resistance to pseudomonal infection and reduction of pyrogenicity. Among the compounds tested, sodium N-acetylglucosaminyl-β(1 → 4)-N-acetylmuramyl-l-alanyl-d-isoglutaminyl-(l)-stearoyl-(d)-meso-2,6-diaminopimelic acid-(d)-amide and sodium N-acetylglucosaminyl-β(1 → 4)-N-acetylmuramyl-l-alanyl-d-isoglutaminyl-(l)-stearoyl-(d)-meso-2,6-diaminopimelic acid-(d)-amide-(l)-d-alanine were found to be advantageous and conceivably worthwhile for further investigation as immunobiologically active compounds.     

Increased Bean (Phaseolus vulgaris L.) Nodulation Competitiveness of Genetically Modified Rhizobium Strains

Rhizobium leguminosarum bv. phaseoli strain collections harbor heterogeneous groups of bacteria in which two main types of strains may be distinguished, differing both in the symbiotic plasmid and in the chromosome. We have analyzed under laboratory conditions the competitive abilities of the different types of Rhizobium strains capable of nodulating Phaseolus vulgaris L. bean. R. leguminosarum bv. phaseoli type I strains (characterized by nif gene reiterations and a narrow host range) are more competitive than type II strains (that have a broad host range), and both types are more competitive than the promiscuous rhizobia isolated from other tropical legumes able to nodulate beans. Type I strains become even more competitive by the transfer of a non-Sym, 225-kilobase plasmid from type II strain CFN299. This plasmid has been previously shown to enhance the nodulation and nitrogen fixation capabilities of Agrobacterium tumefaciens transconjugants carrying the Sym plasmid of strain CFN299. Other type I R. leguminosarum bv. phaseoli transconjugants carrying two symbiotic plasmids (type I and type II) have been constructed. These strains have a diminished competitive ability. The increase of competitiveness obtained in some transconjugants seems to be a transient property.     

小麦根际联合固氮菌(固氮螺菌,Azospirillum brasilense)田间接种效果的研究

据黑龙江省1990年7个中试点试验证明,小麦根际联合固氮菌田间接种效果在5.2—20.6％,平均为9.8％;每田可增产小麦19.1公斤。小麦根际联合固氮菌能促进小麦本长发育,在生育期间可使株高、鲜重增加,叶色变缘。秋收考种证明,对产量构成因子的平方米穗数、穗粒数和千粒重均有增加。     

The Effect of Cycloheximide on Absorption of Ions by Bean (Phaseolus vulgaris L) Roots

10^–7 M cycloheximide inhibited bean (Phaseolus vulgaris)root elongation by about 20 per cent but it inhibited absorptionof rubidium, sodium, and phosphate ions to a much greater extent(34–71 per cent). Tips of intact plant roots grown inthe inhibitor showed more inhibition in ion uptake than adjacentproximal portions of the same roots and this is taken to indicatethat 10^–7 M cycloheximide does not exert its effect onion uptake by any uncoupling action. Sodium uptake from 0.5 or 10 mM NaCl solutions by root tipswas inhibited by 10^–7 M cycloheximide to twice the extentthat it was in the elongating region of the root. Assuming thatthe inhibitor affects the plasmalemma more than the tonoplast,Epstein's model of parallel operation of system 1 and system2 at the plasmalemma is supported.     

Nodulation of Pole Bean (Phaseolus vulgaris L.) by Rhizobium Species of Two Cross-Inoculation Groups

Physiology and morphology of pole bean (Phaseolus vulgaris L. cv Kentucky Wonder) root nodules induced by two Rhizobium species of different cross-inoculation groups have been compared. Root nodules induced by Rhizobium sp. 127E15, which is a strain of the cowpea group Rhizobium, were pinkish, had irregular shapes, and were only partially effective. Their peak acetylene reduction activity was 4.36 μmol of C₂H₄ formed per g of fresh nodules per h at 30 days after inoculation. The effective nodules induced by Rhizobium phaseoli 127K14, which is a strain of the bean group Rhizobium, were dark red, spherical, and showed peak acetylene reduction activity of 15.95 μmol of C₂H₄ formed per g of fresh nodules per h at 15 days after inoculation. The partial effectiveness of 127E15-induced nodules was associated with fewer infected cells, a delay in the increase of bacteroid population within the host cells, abundance of cytoplasmic vesicles in the host cells, more bacteroids within a membrane envelope (peribacteroid membrane), and the inability of bacteroids to completely fill up the host cytoplasmic space. The 127K14-induced nodules were fully mature, with host cells filled with bacteroids by 12 days after inoculation. In contrast, the 127E15-induced nodules did not reach a similar developmental stage even 30 days after inoculation.     

Enzyme-Linked Immunosorbent Assay for Specific Identification and Enumeration of Azospirillum brasilense Cd. in Cereal Roots

The enzyme-linked immunosorbent assay is suggested as a reliable, sensitive, and highly specific method for the identification and enumeration of Azospirillum brasilense Cd. As few as 10⁵ CFU/ml can be practically identified by this method. At higher bacterial numbers, sensitivity increased linearly up to 5 × 10⁸ CFU/ml, yielding useful standard curves. No cross-reaction was found either with different closely related Azospirillum strains or with other rhizosphere bacteria. The method allows for a specific identification of A. brasilense Cd. both in pure cultures and in mixtures with other bacterial species, even when the colony morphology is variable. The method was successfully applied to assess the degree of root colonization on various cereals by A. brasilense Cd.     

Alleviation of Salt Stress in Common Bean (Phaseolus vulgaris) by Exogenous Abscisic Acid Supply

In this work the effect of abscisic acid (ABA) and 100 mM NaCl on common bean (Phaseolus vulgaris var. Coco) growth, nitrogenase activity, and nodule metabolism was studied. Experiments were carried out in a controlled environmental chamber and plants, at the vegetative growth stage (16 days old), were treated with ABA (1 μM and 10 μM) and 48 h later were exposed to saline treatment. Results revealed that plant dry weight, nodule dry weight, nitrogen fixation (acetylene reduction activity and ureides content), and most enzymes of ammonium and ureides metabolism were affected by both ABA and NaCl. The addition of 1 μM ABA to the nutrient solution before the exposure to salt stress reduced the negative effect of NaCl. Based on our results, we suggest that ABA application improves the response of Phaseolus vulgaris symbiosis under saline stress conditions, including the nitrogen fixation process and enzymes of ammonium assimilation and purine catabolism.     

中国普通菜豆形态性状分析及分类

对129份中国普通菜豆地方品种的形态性状进行分析,结果表明,8个性状共检测到35个变异类型,平均变异类型为4.375个,平均多态信息含量为0.5638。中国普通菜豆包括安第斯和中美两个基因库种质,中美洲基因库资源在参试资源中比重较大,但安第斯基因库资源遗传多样性水平高于中美基因库材料。由中美基因库向安第斯基因库渗透的天然杂交种质可为普通菜豆高产、优质、抗逆育种提供有价值的桥梁品种。     

普通菜豆种质资源表型鉴定及多样性分析

对646份普通菜豆核心种质在贵州毕节进行了表型鉴定,结果表明,普通菜豆具有丰富的形态性状多样性。总变异数为367,平均遗传丰富度为8.34,变异范围2~31;遗传多样性指数为0.63,变异范围为0.02~0.91。通过多变量的主成分分析,前3个主成分的贡献率较大,分别为17.73%、15.35%和11.33%。依据表型鉴定数据信息,将供试种质聚类并划分为4组。Ⅰ组的遗传多样性较高,主要为直立有限的大粒资源,大多资源属于安第斯基因库;Ⅱ组的遗传多样性最低,为直立无限生长习性的小粒资源,属于中美基因库;Ⅲ组的遗传多样性最高,主要以蔓生无限为主,包括小部分直立无限和匍匐无限的资源;Ⅳ组的遗传多样性较低,为蔓生无限生长习性、株高最高、分枝数最少的资源。筛选到大粒、多荚、长荚、宽荚等具有特异性状的种质资源35份。     

Mechanism of Zinc Uptake in Bean (Phaseolus vulgaris) Tissues

Uptake of micronutrient zinc by intact leaves, enzymically isolated leaf cells, leaf disks, excised roots, and stem-callus tissue of two field bean cultivars 'Saginaw’ and ‘Sanilac’) was studied using radio-isotope tracer technique. Radio-phosphorus absorption by these tissues was also followed under comparable experimental conditions. A rapid absorption of the micronutrient and strong dependency on external zinc concentration and pH were revealed. Absorption of zinc was not inhibited by respiratory inhibitors (dinitrophenol, azide, cyanide, and amytal), and was not light or temperature dependent. Q₁₀ values for zinc uptake ranged between 1 and 1.2. Uptake of phosphate, on the other hand, was temperature and light dependent and drastically reduced by the presence of metabolic inhibitors. Differences in responses to respiratory inhibitors, temperature, pH, light and darkness, and kinetic data, strongly suggest that zinc uptake in bean tissues occurs primarily by a passive mechanism, involving possibly a physical or physiochemical binding of the micronutrient ions to the cell wall and free space components, and a passive diffusion into the interior of the cell.     

Cellulase and Abscission in the Red Kidney Bean (Phaseolus vulgaris)

Cellulase (β-1, 4-glucan-glucanohydrolase EC 3.2.1.4) activity in the abscission zone of red kidney bean (Phaseolus vulgaris) was previously shown to exist in at least two different molecular forms. The form of the enzyme which has an isoelectric point of 4.5 is present in both abscising and nonabscising tissue and requires grinding for extraction. Another form of the enzyme which has an isoelectric point of 9.5 is present only in tissue in which the abscission process has been induced. Further, much of this form of cellulase can be removed from the tissue by vacuum infiltration with buffer. Time course studies indicate that while the increase in measurable cellulase activity in tissue which is actively undergoing abscission was due primarily to the appearance of cellulase 9.5, this form of the enzyme cannot be removed by vacuum infiltration until after the breakstrength of the abscission zone has decreased nearly to zero. The intracellular localization of these two forms of cellulase is discussed.     

Absorption and translocation of Cd in bush beans (Phaseolus vulgaris)

A series of experiments was conducted to examine some factors affecting the absorption and translocation of Cd in young bean plants ( Phaseolus vulgaris L. cv. Bulgarian). Absorption of Cd by roots was reduced in the presence of other cations of increasing valency or ionic radii. Reduced absorption was also found in the presence of EDTA. Concentration of Cd in exudates from excised stems increased with increased passage of Cd solutions and approached the concentration in the external medium (4.5 μ M Cd). This was apparently associated with saturation of adsorption sites in the stems. The stem behaved as a cation exchange column resulting in a chromatographic distribution of Cd towards the top of the plant. These experiments indicate that Cd existed in the xylem fluid as a free or weakly complexed cation. Additional experiments showed that the total amount of Cd absorbed by bean plants was elevated by inducing higher transpiration rates. The effect of water flux on Cd transport indicated apoplastic flow to the stele.     

Selenate and Selenite Uptake and Translocation in Bean Plants (Phaseolus vulgaris)

After 3 h, selenate uptake by roots of Phaseolus vulgaris L.cv. Contender resulted in more than 50% of the Se absorbed beingconveyed to the aerial organs. This distribution was sensitiveto respiratory inhibitors and when roots were soaked in a solutionsupplied with hydroxylamine, the level of Se decreased by about80% in the whole plant, suggesting that selenate uptake requiresenergy. Addition of glucose to the nutrient medium resultedin slightly decreased uptake and distribution. Under the same growth conditions and 3 h incubation with selenite,a major part of the Se had accumulated in the roots, while asmall fraction was conveyed towards the aerial organs. Thispercentage was decreased by about 20% when plants were transferredto a solution supplied with hydroxylamine, suggesting that partof the selenite entered the roots passively. Addition of glucoseto the nutrient solution, resulted in enhanced levels of Sein the whole plant. Application of plant growth substances affected Se transport.When roots were incubated in abscisic acid (ABA), selenate uptakewas affected, while foliar spraying of gibberellin A₃ (GA₃)enhanced selenite uptake and translocation. Key words: Phaseolus vulgaris, selenate, transport, selenite, glucose, harmones     

Amitrole Absorption by Bean (Phaseolus vulgaris L. cv ;Red Kidney') Roots : Mechanism of Absorption

The mechanism of transport of the herbicide 3-amino-1,2,4-triazole (amitrole) into Phaseolus vulgaris roots appears to be passive, as judged by the effect of temperature (Q₁₀ = 1.3 between 15 and 25°C) and the lack of sensitivity to metabolic inhibition afforded by 2,4-dinitrophenol and NaN₃. Amitrole absorption is a linear function of external concentration over several orders of magnitude and, thus, is not facilitated by a carrier mechanism. The absorption of amitrole is sensitive to external pH, being stimulated under acid conditions. This stimulation of amitrole absorption is seen at low (≤1 millimolar) amitrole concentrations, but not at high (50 millimolar) amitrole levels. While the apparent octanol-water partition coefficient varies with the pH of the aqueous phase, there is no clear correspondence between absorption and the apparent partition coefficient. Roots do not accumulate amitrole above concentration equilibrium; however, at a time when the net amitrole content of the root tissue begins to saturate, amitrole can be detected in the xylem stream. On a fresh-weight basis, amitrole absorption by roots is equal to that accomplished by trifoliate-leaf tissue. An estimate of the permeability coefficient (according to the analysis of Tyree et al. 1979 Plant Physiol 63: 367-374) suggests that amitrole possesses near-optimal permeability for an ambimobile solute, on the order of 2.12 (± 0.47) × 10⁻⁹ meters per second.     

Resistance of Common Bean (Phaseolus vulgaris) to Bacterial Wilt Caused by Curtobacterium flaccumfaciens pv. flaccumfaciens

Bacterial wilt caused by Curtobacterium flaccumfaciens pv. flaccumfaciens is an important new disease of common bean (Phaseolus vulgaris) in western Canada. Both yellow and orange variants of the pathogen were found in the region. A controlled environment study was conducted to assess 124 common bean cultivars and lines from eight market classes for resistance to the yellow and orange variants of the pathogen, using the hilum injury/seed inoculation method. Results of the screening tests showed significant (P < 0.05) differences in resistance to bacterial wilt among the cultivars or lines. The great northern line L02E317, the great northern cultivar Resolute and pinto lines L02B662 and 999S‐2A, were highly resistant to both variants of the pathogen, with disease severity indices of 0 on a rating scale of 0 (no wilt symptoms) to 5 (dead seedling). Resistant cultivars or lines were found among black, great northern, pink, pinto, small red and Flor de Mayo bean market classes. The study concludes that new bacterial wilt‐resistant germplasm exists among Canadian bean cultivars and lines, and constitutes a valuable resource for breeding common beans for resistance to both yellow and orange variants of C. flaccumfaciens pv. flaccumfaciens.