Common Bean Nodules Research Articles

Genotypic diversity and symbiotic effectiveness of rhizobia isolated from root nodules of Phaseolus vulgaris L. grown in Tunisian soils

One hundred and sixty isolates of rhizobia were sampled from the root nodules of common bean (Phaseolus vulgaris L.) cultivated in Tunisian soil samples originating from three geographically distinct fields. Plasmid profiling was used as a primary method to rapidly screen the isolates, and then 38 plasmid types were recorded among the 160 isolates. A sample representing the majority of plasmid types was chosen for further characterization by restriction fragment length polymorphism (RFLP) analysis of genomic DNA using chromosomal and symbiotic gene probes, and by their ability to nodulate a potential alternative host, Leucaena leucocephala. One third of the isolates showed a high similarity to Rhizobium gallicum isolated from common bean in France, another third showed the same characteristics as the R. etli-R. leguminosarum group, while the remaining isolates could not be related to any of the five species nodulating bean. When reexamined for nodulation, some of these isolates, showing similarities to R. tropici and Agrobacterium with respect to colony morphology and growth in different media, failed to nodulate their original host. The R. gallicum-like isolates, R. etli-like isolates, and R. leguminosarum-like isolates were recovered from regions where bean is frequently grown, while in fields which had not been cultivated with beans for at least the 10 previous years, solely unrecognized taxa of ineffective isolates were recovered. We detected variations in the symbiotic regions, but certain pSym RFLP patterns for nifH were conserved between Tunisian, French, and Austrian populations of bean rhizobia. Evaluation of symbiotic effectiveness showed that R. gallicum-like isolates and R. etli-like isolates were effective, whereas some R. leguminosarum-like isolates were ineffective. Furthermore, effective isolates were also found among the unrecognized taxa.

The effects of soil compaction, soil moisture and soil type on growth and nodulation of soybean and common bean

In field tests we have observed year-to-year differences in the severity of the effects of soil compaction on nodulation and growth of common bean; these differences appeared to be related to the amount of rainfall during the growing season. We decided to use better controlled conditions in the greenhouse, and extend the scope of the study to another legume crop and a different soil type, in order to investigate the hypothesis that copious water supply alleviates the adverse effects of soil compaction on nodulation and plant growth.The effects of two levels of soil compaction and of high and low water supply on the growth and nodulation of common bean and soybean were investigated in separate pot tests using a Fox sandy loam and a Brookston clay loam soil.Root growth of both species was severely restricted by dry compacted conditions. Plant growth as a whole was clearly reduced by both increased compaction and by reduced water supply, presumably mediated by the effects on root growth. The effect of reduced water supply was more severe in the highly compacted pots, and more severe in the clay loam than in the sandy loam.In the sandy loam, low moisture reduced nodule numbers and weights in both species, while increased bulk density reduced the numbers of nodules but not the dry weights. In the clay loam, nodule weights and numbers were very low, presumably, owing to high levels of nitrate, which may have resulted from mineralization of soil organic matter during storage.A generous supply of water obviously alleviated some of the adverse effects of soil compaction on plant growth. This is in general agreement with results of earlier field trials, where severity of the effects of soil compaction varied with the quantity of rainfall. Key words: Soybean, common bean, soil compaction, soil moisture, nodulation, bulk density

Nodulation and growth of common bean under NaCl-stress

Nodulation and growth of common bean under NaCl-stress

Antioxidant defenses in the peripheral cell layers of legume root nodules.

Ascorbate peroxidase (AP) is a key enzyme that scavenges potentially harmful H2O2 and thus prevents oxidative damage in plants, especially in N2-fixing legume root nodules. The present study demonstrates that the nodule endodermis of alfalfa (Medicago sativa) root nodules contains elevated levels of AP protein, as well as the corresponding mRNA transcript and substrate (ascorbate). Enhanced AP protein levels were also found in cells immediately peripheral to the infected region of soybean (Glycine max), pea (Pisum sativum), clover (Trifolium pratense), and common bean (Phaseolus vulgaris) nodules. Regeneration of ascorbate was achieved by (homo)glutathione and associated enzymes of the ascorbate-glutathione pathway, which were present at high levels. The presence of high levels of antioxidants suggests that respiratory consumption of O2 in the endodermis or nodule parenchyma may be an essential component of the O2-diffusion barrier that regulates the entry of O2 into the central region of nodules and ensures optimal functioning of nitrogenase.

Effects of Azospirillum brasilense on nodulation and growth of common bean ( Phaseolus vulgaris L.)

Combined inoculation of potted common bean plants with Rhizobium and Azospirillum significantly increased both upper and total nodule number and N 2-fixation as compared with inoculation with Rhizobium alone. At an Azospirillum concentration of 10 8 cfu ml −1, the combined inoculation reduced root and shoot dry weight accumulation in comparison with Rhizobium alone and with uninoculated controls. However, when the combined inoculation was performed using a lower Azospirillum concentration (5 × 10 6 cfu ml −1), positive effects on plant growth were observed, although the enhancement of nodulation and N 2-fixation were not as great as observed at the higher Azospirillum concentration. Field application of these findings are discussed.

Promotion of nod Gene Inducers and Nodulation in Common Bean (Phaseolus vulgaris) Roots Inoculated with Azospirillum brasilense Cd

Inoculation of Phaseolus vulgaris with Azospirillum brasilense Cd promoted root hair formation in seedling roots and significantly increased total and upper nodule numbers at different concentrations of Rhizobium inoculum. In experiments carried out in a hydroponic system, A. brasilense caused an increase in the secretion of nod gene-inducing flavonoids, as was observed by nod gene induction assays of root exudates fractionated by high-performance liquid chromatography. Possible mechanisms involved in the influence of A. brasilense on this symbiotic system are discussed.

The effects of soil compaction on nodulation and growth of common bean (Phaseolus vulgaris L.)

As part of an investigation of factors limiting nodulation in the field, cultivars of common bean were grown in a sandy loam soil that had been either deep tilled (DT) to reduce compaction or repeatedly rolled by a golf cart or by a tractor followed by a golf cart. In 1991 and 1992, the tractor-rolling treatment was replaced by a conventional tillage system. Nineteen cultivars were grown in 1990; 10, in 1991; and 4, in 1992. In general, soil compaction decreased plant growth and yield but had no adverse effect on numbers or weights of nodules per plant. In 1990, nodule numbers and weights were increased by compaction in the first sample, 35 d after planting. In a combined analysis of the four cultivars common to all 3 yr, nodule weight as a fraction of total plant weight was increased by compaction. Thus, compaction had a more severe effect on overall plant growth than on nodulation per se. Numbers and weights of nodules differed among the cultivars, but they all responded similarly to compaction. Cultivars yielded differently, depending on the degree of compaction (i.e., cultivar × compaction interaction), but, even so, the cultivar that had the highest yield in the DT plots also had the highest yield in the compacted plots. For most characteristics, the severity of the effects of compaction varied with the year, presumably in response to different weather conditions. Key words: Bean yield, common bean, nodulation, Phaseolus vulgaris, soil compaction

Effects of a Seed Color Mutation on Rhizobialnod-Gene-Inducing Flavonoids and Nodulation in Common Bean

Effects of a Seed Color Mutation on Rhizobial<i>nod</i>-Gene-Inducing Flavonoids and Nodulation in Common Bean

Ontogenetic Changes in Root Nodule Subpopulations of Common Bean (Phaseolus vulgarisL.)

Root nodules of common bean (Phaseolus vulgaris L. GN 1140) show different ontogenetic patterns of nitrogen fixation in different parts of the root system. The objective of the present study was to search for nodule physiological factors which could explain these differences. Plants were grown to maturity under controlled environment conditions. Root nodules were regularly harvested from two zones of the root system, and assayed for soluble cytosolic content and carbohydrate status. Nodule concentrations of soluble carbohydrates, glucose, fructose or sucrose, did not change significantly during the pod-filling decline in nitrogenase activity. Nodule concentrations of sucrose appeared more related to nodule ontogeny than to the ontogenetic stage of the shoot

Cultivar Variation in Traits Affecting Early Nodulation of Common Bean

Phaseolus vulgaris L. is inferior to other grain legumes in nodulation and N2 fixation, with early‐flowering cultivars particularly limited in the ability to satisfy their N needs through fixation. Extending the period of fixation could reduce the dependence of this crop on N‐fertilization. We sought bean accessions that were early to nodulate, and tried to identify specific traits that contributed to this ability. A root‐tip marking procedure was used to evaluate the earliness in nodulation of 40 accessions of common bean. With Rhizobium leguminosarum bv. phaseoli strain UMR1084 the accessions varied in uppermost nodule position relative to the root‐tip mark (RTM; −2.05 mm to +6.12 mm), number of nodules produced above the RTM (0.57‐3.93), and percentage of plants nodulated above this mark (37.7‐ 97.1%). Cultivars nodulated earlier with strain UMR1084 and UMR1899 than with strain UMR1242. Accessions RIZ23, RIZ108, N80068, and WI21‐58 nodulated rapidly with all strains tested, while ‘Mantequilla tropical’, RIZ21, and 0051 were slow to nodulate. selected bean accessions were then examined for inoculum dose response with UMR1084, for the percentage of infection sites giving rise to nodules, for the rate of development of nodules in the period 16 to 25 days after planting (DAP), and for plant growth and accumulation of N at 51 DAP. In these studies, ‘Puebla 152’ showed excellent nodule development and growth to the 25 DAP harvest, while the experimental line RIZ21 accumulated significantly more N and grew better in the period 25 to 51 DAP. The differences between these two accessions could be exploited in breeding programs for enhanced nodulation and N2 fixation in common bean.

Low nitrogen fixation of common bean (phaseolus vulgarisL.)

Abstract Nitrogen fixation activity in legumes varies among species and common bean (Phaseolus vulgaris L.) is known to exhibit a lower ability to fix nitrogen than other legumes such as soybean (LaRue and Patterson 1981; Nishimune et al. 1983). Therefore, the dependence of common bean on nitrogen fertilizer is considerably higher than that of soybean (Matsushiro 1971). At least, three factors may contribute to the low nitrogen fixation observed in common bean: (1) delay of nodule appearance on root system, (2) insufficient nodule mass on root system, and (3) ineffectiveness of nodules formed on root system. In this paper, the nodulation and nitrogen fixation of common bean and soybean were investigated using the root-box-culture technique.

Influence of Oxygen and Acetylene during in situ Open-flow Assays of Nitrogenase Activity (C 2H 2 Reduction) in Phaseolus vulgaris Root Nodules

Summary An open-flow gassing system was used to measure the acetylene reduction activity of undisturbed root nodules of hydroponically grown common bean ( Phaseolus vulgaris ). There was no detectable inhibition by acetylene during the acetylene reducing activity (ARA) assay in plants before the flowering stage. After this stage, ARA declined rapidly upon exposure of nodulated roots to acetylene (C 2 H 2 ) and this decline was more severe in older plants. The presence of a steady phase under C 2 H 2 in younger plants made it possible to observe the effects of external O 2 tensions on ARA. The nitrogenase activity was optimal for 35 and 50 Kpa O 2 at the vegetative and preflowering stages, respectively. This suggests that in the soil gas phase, containing no more than 21% O 2 , nitrogen fixation by young common bean nodules is limited by oxygen.

Nodulin Regulation in Common Bean Nodules Induced by Bacterial Mutants

Nodulin Regulation in Common Bean Nodules Induced by Bacterial Mutants

Soil Acidity and Liming Effects on Stand, Nodulation, and Yield of Common Bean

AbstractThe area planted to common bean (Phaseolus vulgaris L.) has been declining in the Southern Mexican State of Chiapas. To determine factors limiting bean productivity in this region, on‐farm experiments were conducted at four locations. Soils were Acrisols (Ustults) at two sites and a Cambisol (Tropept) and Phaeozem (Ustoll) at the other two sites, with pH (H2O) of unlimed soil from 4.6 to 5.0. Insecticide application, genotype, and lime were treatments in a split‐plot design with a factorial combination of two genotypes and 0 or 2000 kg Ca(OH)2 ha−1 as subplots. Across sites, lime addition raised soil pH by 0.4 to 1.3 units, decreased Al saturation by 13 to 38%, and increased extractable Ca two‐to three‐fold. Mean yield without lime was 444 kg ha−1 ha. Insecticide and bean genotype had negligible effects on yield. Lime application resulted in a yield increase of 76 to 313% above unlimed controls across locations. Liming resulted in 40% greater shoot and 18% greater root dry weight, and also improved nodule weight per plant by 110% at early flowering. At maturity, plant density in limed treatments was 23% higher than in unlimed controls, and counts made during the season indicated that soil acidity factors inhibit seedling establishment. Liming also increased pod number per plant by 67%, seed number per pod by 18%, and seed weight by 7%. Increased yield from lime therefore resulted from better stand establishment, and increased seed yield per plant. Increased nodulation and N2 fixation may also contribute to the response to lime.

Host Plant Traits Associated with Estimates of Nodulation and Nitrogen Fixation in Common Bean

Abstract Field and greenhouse experiments were conducted to study the relationships among plant growth traits; ratios of dry weights among nodules, roots, and shoots; and traits associated with N2-fixation potential of common bean (Phaseolus vulgaris L.). The dry weights of plant parts and the traits associated with N2-fixation differed among the 10 lines studied. A visual nodulation score used to evaluate N2-fixation potential was correlated positively with nodule dry weight, acetylene reduction (AR) value, root dry weight, and shoot dry weight for plants grown under both greenhouse and field conditions. AR values, nodule dry weight, and visual nodule scores of plants grown in the greenhouse were correlated positively with the respective figures obtained for field-grown plants. These methods of evaluation can be used to discriminate among lines for N2-fixation potential.

Influência do EPTC na nodulação natural de feijão (Phaseolus vulgaris L.)

Três experimentos de campo foram instalados em solos com diferentes texturas, aplicando - se o herbicida EPTC, nas doses de 0, 1, 2, 4, 8 e 16 kg/ha, para verificar o seu efeito sobre a nodulação natural em feijão. Os nódulos foram amostrados no início do florescimento, sendo contados e obtendo-se o peso da matéria seca. As produções de sementes foram obtidas no final do ciclo. Em nenhum dos experimentos verificou -se diferença significativa no número ou no peso de nódulos para qualquer das doses aplicadas . Apenas em um dos experimentos houve redução sig - nificativa da produção de grãos com a aplicação das doses de 8 e 16 kg/ha de EPTC.