Characterization of Rhizobia from Ineffective Alfalfa Nodules: Ability to Nodulate Bean Plants [Phaseolus vulgaris (L.) Savi.]

This study was initiated to characterize Rhizobium isolates obtained from root nodules of ineffectively nodulated, field-grown alfalfa (Medicago sativa L.) plants. The purpose was to determine if these isolates possessed characteristics which would explain either their ineffectiveness in N₂ fixation or their apparent ability to tolerate the moderately acid soil conditions from which they originated. Isolates were characterized by analysis of growth rate, 39°C tolerance, acid production on conventional media, and symbiotic performance. All isolates were ineffective in N₂ fixation on alfalfa, and they contained one or more anomalous characteristics. These included either slow growth rate, lack of 39°C tolerance, or lack of acid production on conventional media. Infectiveness tests on a broad range of legumes revealed that the isolates formed root nodules on M. sativa, Medicago lupulina L., and Phaseolus vulgaris (L.) Savi. (common bean). These results provide evidence that, in some situations, ineffective nodulation of M. sativa in the field may be due to the presence of promiscuous, native Rhizobium species.     

Subunit Composition of Glutamine Synthetase Isozymes from Root Nodules of Bean (Phaseolus vulgaris L.)

Glutamine synthetase from bean nodules can be separated into two isoforms, GS_n1 and GS_n2. A purification protocol has been developed. It included protamine sulfate precipitation, ammonium sulfate fractionation, anthranilate-affinity chromatography, Dye-Matrex (Orange A) chromatography, and diethylaminoethyl-cellulose ion-exchange chromatography. GS_n1 and GS_n2 have been purified to homogeneity. Subunit structure analysis using two-dimensional polyacrylamide gel electrophoresis revealed that GS_n1 was composed of two different types of subunit polypeptides. They differed in isoelectric points (6.0 and 6.3) but had the same molecular weights (46,000 Daltons). GS_n2 was composed of only one type of subunit polypeptide. It had an isoelectric point of 6.0 and a molecular weight of 46,000 Daltons. It was apparently identical to one of the polypeptides found in GS_n1. Glutamine synthetase holoenzyme consisted of eight subunits. In the nodule there are two different types of glutamine synthetase subunit polypeptides. Random combinations of the polypeptides should generate nine different isozymes. Our electrophoretic analysis revealed that GS_n2 was but one of the isozymes, and GS_n1 was a composite of the other eight. Hence, nodule glutamine synthetase isozymes were homo-octameric as well as hetero-octameric.     

The Development of Flower Primordia of Phaseolus vulgaris (L.) Savi.

The first-formed flower primordium on determinate varieties(plants with terminal inflorescences) of Phaseolus vulgarishas been identified and located. Irrespective of the numberof leaves on the main stem, it is formed directly in the axilof the uppermost leaf. The physiological significance of thisis discussed.     

Effect of Glyphosate on Intact Bean Plants (Phaseolus vulgaris L.) and Isolated Cells

Whole bean (var. “Eastern Butterwax”) plants and isolated cells were used to investigate possible mechanisms of action of glyphosate [N-(phosphonomethyl)glycine]. Results showed that glyphosate was quickly absorbed by the whole plant but not by individual cells and that it caused a rapid reduction in leaf dry matter accumulation, leaf expansion, leaf angle, and stomatal aperture without affecting the water status of the plant. Glyphosate also caused a rapid reduction in cellular uptake of ⁸⁶Rb and ³²P which preceded its detrimental effects on photosynthesis, RNA and protein synthesis, and respiration of isolated cells. This reduction in ion absorption was not due to a loss of membrane integrity, decrease in energy supply or chelation of ions. It was concluded that glyphosate was directly inhibiting the ion absorption process of bean leaf cells.     

Pathogenicity of Pratylenchus penetrans to Navy Bean (Phaseolus vulgaris L.)

The pathogenicity of Pratylenchus penetrans (root-lesion nematode) to Phaseolus vulgaris (navy bean) was evaluated in greenhouse experiments. Shoot and root fresh weight of cv. Sanilac plants were increased 4 and 21%, respectively, by an initial population density (Pi) of 25 P. penetrans per 100 cm³ soil. Leaf area and shoot fresh and dry weights were decreased by a Pi of 50 or more P. penetrans per 100 cm³ soil. A significant positive linear relationship existed between initial soil population densities of P. penetrans and final soil and root population densities of this nematode. Three dry bean cultivars, Sanilac, Seafarer, and Tuscola, were susceptible to P. penetrans, and yields were reduced by 43-76% when plants were exposed to a Pi of 150 P. penetrans per 100 cm³ soil. P. penetrans also reproduced on bean cultivars Saginaw, Gratiot, and Kentwood, but did not decrease bean yields, suggesting that these cultivars were tolerant to this nematode.     

Chromium VI Induced Structural and Ultrastructural Changes in Bush Bean Plants (Phaseolus vulgaris L.)

The effect of a growth reducing chromium VI concentration (9.6x 10^–5M Cr as Na₂CrO₄) on the structure and ultrastructureof different organs of bush bean plants (Phaseolus vulgarisL.) grown on perlite was studied using light, transmission electronand scanning electron microscopy. The structural and ultrastructuralalterations observed were quite different in the various organsanalysed and did not always stay in direct relation to the averageCr content of the whole organ. The primary toxicity effect seemedto be membrane damage, due to the high oxidation power of CrVI. It is suggested that chromium is retained in vacuoles andcell walls of roots, and that the chromium reaching the leavesmay be principally Cr III and present in cell walls. The alterationsobserved in the upper plant parts seemed principally due toindirect Cr effects on the content of essential mineral nutrients. Phaseolus vulgaris L., bush bean, chromium VI toxicity, structure, ultranstructure, light microscopy, transmission electron microscopy, scanning electron microscopy     

Thigmotropism in Organs of the Bean Plant (Phaseolus vulgaris L.)

When each vegetative aerial organ of the young bean plant isunilaterally mechanically perturbed by gentle rubbing, it exhibitspositive thigmotropism. The internodes undergo only moderatethigmotropism, but leaves and petioles bend much more, especiallywhen they are rubbed on their abaxial surfaces. When the abaxialsurface of one petiole is rubbed, it bends down, but the oppositepetiole bends upward at the stem-petiole pulvinus. These observationsare interpreted in terms of the vining habit of bean plants. Bean, Phaseolus vulgaris, thigmotropism, mechanical perturbation     

On Vessel Member Differentiation in the Bean (Phaseolus vulgaris L.)

Certain ultrastructural features of vessel member differentiationwere examined in the primary xylem of petiole of bean (Phaseolusvulgaris L.). The cells used had helical secondary wall thickeningsand simple perforation plates. The primary cell wall increasesin thickness before the helices of secondary wall develop. Ina common wall between two vessel members of different ages,theprimary thickening occurs first in the older cell so thatfor a time the middle lamella is located closer to the youngercell rather than medianly. Apparently the helix is depositedafter the primary wall of a given cell reaches maximum thickness.The perforation of the end wall is preceded by primary thickeningof the part of the wall that is later removed. The marginalregion remains relatively thin and becomes covered with a rimof secondary wall. Vesicles with fibrous content appear nearthe surface within the end wall shortly before the perforationoccurs. A highly vacuolated protoplast with a much enlargednucleus and numerous organdIes is present during cell wall differentiation.After that process is completed, the protoplast disintegratesand the primary wall bearing the helix is hydrolysed where itis exposed to the cell lumen and, under certain conditions,also under the secondary wall.     

Leaf Gas Exchange of Bean (Phaseolus vulgaris L.) Seedlings Subjected to Manganese Stress

Russian Journal of Plant Physiology - Manganese (Mn) is a microelement required for optimal growth of plants and involved in several metabolic processes, mainly in photosynthesis. In the present...     

Effect of Salt Stress on Carbon Metabolism and Bacteroid Respiration in Root Nodules of Common Bean (Phaseolus vulgaris L.)

Abstract: In the present work, we examined the effect of salinity on growth, N fixation and carbon metabolism in the nodule cytosol and bacteroids of Phaseolus vulgaris, and measured the O₂ consumption by bacteroids incubated with or without the addition of exogenous respiratory substrates. The aim was to ascertain whether the compounds that accumulate under salt stress can increase bacteroid respiration and whether this capacity changes in response to salinity in root nodules of Phaseolus vulgaris. The plants were grown in a controlled environment chamber, and 50, 100 mM or no NaCl (control) was added to the nutrient solution. Two harvests were made, at the vegetative growth period and at the beginning of the reproductive period. The enzyme activities in the nodule cytosol were reduced by the salt treatments, while in the bacteroid cytosol the enzyme activities increased at high salt concentrations at the first harvest and for ADH in all treatments. The data presented here confirm that succinate and malate are the preferred substrates for bacteroid respiration in common bean, but these bacteroids may also utilize glucose, either in control or under saline conditions. The addition of proline or lactate to the incubation medium significantly raised oxygen consumption in the bacteroids isolated from plants treated with salt.     

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。     

Subcellular Localization of Zinc and Calcium in Bean (Phaseolus vulgaris L.) Tissues

Two bean (Phaseolus vulgaris L.) cultivars differing in growth responses to zinc were examined for differences in uptake and subcellular localization of ⁶⁵Zn during a 15-day growth period. The zinc-sensitive cultivar Sanilac showed initially a much higher rate of absorption, which declined after 24 hours. The zinc-tolerant cultivar Saginaw showed a slow but steady rate of absorption for 10 days. In roots as well as in stem callus tissues of both cultivars, three-fourths of the absorbed ⁶⁵Zn was localized in the “cytoplasmic” supernatant fractions (containing ribosomes and vacuolar sap). Very little (less than 7%) ⁶⁵Zn was localized in the cell wall fraction. There was a much greater proportion of the absorbed ⁶⁵Zn localized in root mitochondria and nuclei of the zinc-sensitive Sanilac than in the zinc-tolerant Saginaw. Stem callus tissues, however, did not show such cultivar differences in zinc accumulation at the sub-cellular level.     

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.     

Semienclosed Tube Cultures of Bean Plants (Phaseolus vulgaris L.) for Enumeration of Rhizobium phaseoli by the Most-Probable-Number Technique

The semienclosed tube culture technique of Gibson was modified to permit growth of common bean (Phaseolus vulgaris L.) roots in humid air, enabling enumeration of the homologous (nodule forming) symbiont, Rhizobium phaseoli, by the most-probable-number plant infection method. A bean genotype with improved nodulation characteristics was used as the plant host. This method of enumeration was accurate when tubes were scored 3 weeks after inoculation with several R. phaseoli strains diluted from aqueous suspensions, peat-based inoculants, or soil. A comparison of population sizes obtained by most-probable-number tube cultures and plate counts indicated that 1 to 3 viable cells of R. phaseoli were a sufficient inoculant to induce nodule formation.     

Common Bean (Phaseolus vulgaris L.) Mutants Defective in Root Nodule Formation: I. PHYSIOLOGICAL CHARACTERIZATION

Two ineffectively nodulating, allelic mutants of the commonbean (Phaseolus vulgaris L.) lines RIZ30 and RIZ36 were studied.In both mutants the nodulation phenotype was characterized bythe formation of tumour-like swellings when inoculated withbean Rhizobium strains. Late formation of pink nodules was observedin mutant plants grown in pots with soil or in hydroponic conditionswith perlite. In the absence of mineral nitrogen, mutant growthand nodulation were poor; a low peak of acetylene reductionactivity being detected 45 d after inoculation. Mutant growthin the presence of mineral nitrogen was similar to that of thewild type. The mutants were also characterized by poor pod fertility(seed per pod). The nodulation and pod fertility phenotypesare specifically controlled at the root and shoot levels, respectively,as assessed with grafting experiments. Mutant shoots graftedon wild type, nitrogen-fixing roots produced a number of seedssimilar to the wild type despite the expression of the poorpod fertility phenotype. Nitrogen and seed yields of wild typeshoots, grafted on mutant, ineffectively nodulating roots wereseverely reduced when compared with control wild type plantsalthough nitrogen accumulation during vegetative phase was similar. Key words: Phaseolus valgaris, nitrogen fixation, nodulation mutants, grafting, nitrogen assimilation     

Cell-Wall Proteins Induced by Water Deficit in Bean (Phaseolus vulgaris L.) Seedlings

In the last few years, much attention has been given to the role of proteins that accumulate during water deficit. In this work, we analyzed the electrophoretic patterns of basic protein extracts, enriched for a number of cell-wall proteins, from bean (Phaseolus vulgaris L.) seedlings and 21-d-old plants subjected to water deficit. Three major basic proteins accumulated in bean seedlings exposed to low water potentials, with apparent molecular masses of 36, 33, and 22 kD, which we refer to as p36, p33, and p22, respectively. Leaves and roots of 21-d-old plants grown under low-water-availability conditions accumulated only p36 and p33 proteins. In 21-d-old plants subjected to a fast rate of water loss, both p33 and p36 accumulated to approximately the same levels, whereas if the plants were subjected to a gradual loss of water, p33 accumulated to higher levels. Both p36 and p33 were glycosylated and were found in the cell-wall fraction. In contrast, p22 was not glycosylated and was found in the soluble fraction. The accumulation of these proteins was also induced by abscisic acid (0.1-1.0 mM) treatment but not by wounding or by jasmonate treatment.