Bean Roots Research Articles

Pottery Use and Starchy Foods During the Shuangdun Culture (ca.7.3–6.8 Ka BP) in the Middle Catchment of the Huai River, China

The use of rice and millet has been uncovered at a few archaeological sites associated with the Shuangdun Culture (ca. 7.3–6.8 ka BP) in the middle catchment of the Huai River, China. Nevertheless, the consumption of rice, millet, and other types of plant foods at other contemporaneous sites in the same region still needs supporting information from more case studies. This article examines pottery sherds (n = 21) excavated from another representative Shuangdun Culture site at Houjiazhai with starch grain analysis. Varied types of pottery vessels contain starch remains from rice (Oryza sativa), foxtail millet (Setaria italica), broomcorn millet (Panicum miliaceum), Job’s tears (Coix lacryma-jobi), Triticeae, roots of snake gourd (Trichosanthes kirilowii), lotus root (Nelumbo nucifera), Chinese yam (Dioscorea panthainca), lily bulbs (Lilium sp.), acorns (Quercus sp.), and beans (Vigna sp. or/and Vicia sp.). Further quantitative analysis of the starch data indicates that cereals, including rice and millet, were predominantly consumed in the pottery vessels. Changes and continuities of culinary practices are also present at Houjiazhai, which are reflected in the different pottery assemblages as well as the utilized plant species in different occupation phases at the site. Combining previous studies, this article also reveals the differences and similarities of the past population in choosing their plant food resources during the period of Shuangdun Culture in the middle catchment of the Huai River, China.

Phytotoxicity assessment study of gold nanocluster on broad bean (Vicia Faba L.) seedling

ABSTRACT In this study, we investigated the phytotoxicity of gold nanoclusters (AuNCs) on seed germination capacity, physiological response to stress and uptake, and the transport of gold nanomaterials in broad beans. Although similar findings were observed for AuNCs on broad bean root tip cells between micronucleus assays and traditional phytotoxicity experiments, the former was more sensitive and rapid. At experimental concentrations of 0–200 mg/L, the toxicity performance of broad bean seedlings showed an overall positive correlation with the concentration of AuNCs. AuNCs posed a potential risk to the environment at a concentration of 20 mg/L. Moreover, studies on the uptake and transport of gold nanomaterials showed that the smaller the particles entering the bean, the higher the transport coefficient, while materials not entering the bean were mainly adsorbed on the root surface of the bean seedlings by competition with potassium ions.

​​An Agrobacterium rhizogenes Strain R1000-mediated Efficient Hairy Root Transformation Protocol for Common Bean

Background: Common bean (Phaseolus vulgaris L.) is a globally important grain and vegetable legume crop, providing a substantial portion of the diet protein and minerals for many people in the developing world. However, the genetic studies and improvement on this crop has long been impeded by its recalcitrance to Agrobacterium-mediated whole plant genetic transformation. Established Agrobacterium rhizogenes-based hairy root transformation in common bean heavily relies on the strain K599. Methods: In order to develop an efficient alternative protocol for hair transformation in common bean, the efficiency of Agrobacterium rhizogenes strain R1000 in inducing hairy roots from 6-day-old seedlings with root below cotyledons excised by the soaking and smearing method were tested. The binary plasmid pBI121 with the reporter gene GUS (pBI121-GUS) or eGFP (pBI121-eGFP) driven by the constitutive promoter was used for transformation and rapid identification of the transgenic hairy roots. Result: We established a strain R1000-based system for the induction of hairy roots in common bean. The plant receptor genotypes and infection methods were optimized, which led to a high transformation rate of hairy roots up to 60%. This method therefore provides a useful alternative means for functional genomic studies in common bean.

Comparative study between fungicides and some chemical inducers for controlling root rot incidence of green bean (Phaseolus vulgaris L.) under field conditions

Root rot disease caused by Rhizoctonia solani J.G. Kuhn and Fusarium solani (Mart.) Sacc. is a major problem restricting profitable farming of green bean (Phaseolus vulgaris L.). Under field conditions, some chemical inducers compared with chemical fungicides were evaluated for controlling bean root rot disease. Significant effect was observed for all applied treatments against disease incidence compared with control. Applied treatments of seed dressing plus foliar spray showed the highest reduction of root rot incidence followed by seed dressing then foliar spray. Salicylic acid as seed followed by foliar spray showed the highest suppressive effect against disease incidence followed by glutathione treatments. Furthermore, application of calcium silicate revealed higher effect against disease incidence compared with potassium and sodium silicate at both pre-, and post-emergence plant growth stages. Fungicidal treatments showed affect disease incidence in a lower extent compared with Plant Resistance Inducers (PRI). Treatment of Rizolex T50 followed by Topsin M70 was more effectively in controlling root rot than each fungicide alone. Such applied treatments could be useful for controlling root rot disease under field conditions.

The endophyte Stenotrophomonas maltophilia EPS modulates endogenous antioxidant defense in safflower (Carthamus tinctorius L.) under cadmium stress

Cadmium (Cd) pollution in agricultural soils induces oxidative stress in plants that in turn is the foremost limiting factor for agricultural productivity. In past few decades, plant–metal–microbe interaction is of great interest as an emerging environmentally friendly technology that can be exploited to alleviate metal stress in plants. Considering these, in the present study an endophytic bacterium strain EPS has been isolated from the roots of common bean. The present strain was identified as Stenotrophomonas maltophilia based on 16S rRNA gene sequence. The strain showed Cd tolerance and Cd-adsorption potentials. The inoculation of strain EPS in safflower seeds significantly enhanced the antioxidant defense of plants under Cd-stress conditions through increasing the levels of antioxidant molecules like phenolics, flavonoids and carotenoids as well as improving the activities of the antioxidative enzymes including guaiacol peroxidase (POX), ascorbate peroxidase (APX) and superoxide dismutase (SOD). The output of this study is that strain EPS inoculation mitigates Cd-induced oxidative stress and consequently it may be beneficial, especially in Cd-contaminated crop fields.

Isolation and Screening of Efficient Rhizobial Strains and Evaluation of Their Efficiency in Moth Bean (Vigna aconitifolia Jacq)

Background: Moth bean (Vigna aconitifolia Jacq.) is a legume possess a higher nutritional value with 22–24 per cent protein and also used as a pasture legume. Fertilizer applications to moth bean are uncommon in India and mostly grown with minimum inputs and care. The main objective is to increase the production and productivity in moth bean crop, using crop or location specific, native rhizobial strains. Methods: In vitro studies on isolation and characterization of Rhizobium from moth bean root nodules was carried out and further its efficiency was tested under pot culture conditions. Result: Among the thirty isolates obtained, 11 showed positive reactions for poor growth on glucose peptone agar medium, Keto-lactose and catalase activities, citrate utilization in in vitro studies and were tentatively identified as Rhizobium. By 16S rRNA sequencing and culture number MB-1 was identified as Rhizobium skierniewicense. Biometric observations revealed that MB-1 inoculated plants significantly recorded the highest plant height of 34 cm; root length of 14 cm; 24 numbers of leaves per plant having the maximum nodule number of 27 and maximum number of pods of 39 pods plant-1 and its corresponding single plant yield of seeds 18.6 g followed by COG15 inoculated plants which recorded 15.5 g of seeds in a plant. The native isolates Rhizobium skierniewicense, (MB-1) proven to be a effective strain resulted in higher and bigger nodules, increased biometrics and yield attributes.

EFFECT OF INOCULATING Bradyrhizobium liaoningense ON GROWTH, CHLOROPHYLL CONCENTRATION, NODULATION AND YIELD OF SOYA BEANS

Soya bean is important staple food crops in Western Kenya. Legumes play a significant role in agriculture by fixing nitrogen. Currently Kenya is experiencing low yield of soya beans. Approximately 0.8 t/ha is under production and this is due to low soil fertility. This has posed a threat to agricultural productivity. Symbiotic rhizobia inoculation increases crop yields through biological nitrogen fixation. However, the potential of Bradyrhizobium liaoningense in improving yield and productivity of soya beans has not been documented. Rhizobia bacteria are known to improve growth and yield of several other crops but the effect of inoculating soya beans with B. liaoningense on growth, chlorophyll concentration, nodulation and yields has not been determined. This study was conducted at Maseno University under greenhouse conditions. Previously purified local isolates of B. liaoningense (S3) from wild soya beans plants were used to inoculate the soya bean seeds. 4.5 litre plastic pots were filled with 7kg of top soil. Ten seeds of Soya beans coated with Bradyrhizobium liaoningense inoculants were sown in each pot except the control. The seeds were treated with the isolates inoculants as: un-inoculated (control), 1.07x107 cfu/ml, 1.19x107 cfu/ml, 1.31x107 cfu/ml and 2.67x107 cfu/ml inoculation of B. liaoningense. The experiment was laid out as Completely Randomised Design (CRD). The treatments were replicated three times. After two weeks of germination, the seedlings were thinned to three plants per pot. Watering was done daily with 200 ml of water per pot up to the end of the experiment. Data on plant height, number of leaves, leaf area, shoot and root fresh weight and dry weight, chlorophyll concentration, number of nodules and number of pods were determined. Data was subjected to Analysis of Variance (ANOVA). Treatments means were separated using Fisher’s Least Significant Difference at (P = 0.05). Soya bean growth, chlorophyll concentration, number of nodules and number of pods after inoculation treatments were significantly different among the treatments (P ≤ 0.05). Plant height, number of leaves and leaf area were highest in 2.67 x 107 cfu/ml of B. liaoningense inoculation followed by 1.31x 107 cfu/ml inoculation, 1.19x107 cfu/ml, 1.07x107 cfu/ml and lowest in un-inoculated. Inoculation at 2.67 x 107 cfu/ml significantly increased soya bean root and shoot fresh weight and dry weights. Chlorophyll concentration was found to be highest in 2.67 x 107 cfu/ml treatment and lowest in un-inoculated control treatment. Inoculation at 2.67 x 107 cfu/ml increased the number of nodules of soya beans. Number of pod per plant were highest at 2.67 x 107 cfu/ml treatment and lowest in un-inoculated (control treatment). These findings showed that B. liaoningense inoculation was effective in enhancing growth, chlorophyll synthesis, formation of root nodules and pods in soya beans. From the study it can be recommended that B. liaoningense from wild soya bean may be used as a biofertiliser to improve productivity of soya beans by smallholder farmers in Kenya.

Analysis of Trichoderma harzianum TR 274 secretome to assign candidate proteins involved in symbiotic interactions with Phaseolusvulgaris

Trichoderma spp can colonize host plants protecting them from pathogen infection. This association is accomplished by an exchange of molecules secreted by both the host plant and symbiotic fungus. In the present work, using LC-MS/MS analysis, our research group described a list of proteins secreted by T. harzianum TR274 during association with common bean (Phaseolus vulgaris). The main goal is to describe candidate proteins critical for the formerly mentioned association and understand mechanisms related to hosting plant tissue's colonization and modulation of bean plant defense response or metabolism. T. harzianum TR 274 could colonize common bean roots, increasing the transcript levels of defense-related genes (chit, glu1, and pal). Secretomes were obtained from culture filtrates harvested after the growth of T. harzianum TR 274 in the presence (Secretome of co-cultivation-SCC) or absence (Secretome of fungus condition-SFC) of the host plant. We identified 124 and 190 fungal proteins in SCC and SFC, respectively. A total of 30 proteins were detected only in SCC, and 94 were detected in both secretomes (SCC and SFC). The host plant presence decreases the number and diversity of proteins secreted by T. harzianum. The main functional categories represented are glycoside hydrolases, proteases, oxidoreductases, and SSCPs (Small soluble cysteine-rich secreted proteins). Our results provide a list of protein candidates for functional gene studies and validate their role in interactions between T. harzianum and P. vulgaris. Therefore, it contributes to understanding the main mechanisms of T. harzianum host plant colonization and the modulation of defense response.

Effects of the Preceding Crop on Soil N Availability, Biological Nitrogen Fixation, and Fresh Pod Yield of Organically Grown Faba Bean (Vicia faba L.)

In the current study, the impact of the preceding crops on growth, fresh pod yield, nitrogen fixation efficiency, and nitrogen nutrition of faba bean (Vicia faba L.) was investigated for two years in both organic and conventional crops. As preceding crops served cabbage, pea, and faba bean. The pod number per plant (PN) and the total fresh pod yield (TFPY) were significantly lower with cabbage compared to pea and faba bean as preceding crops in both cropping systems and both experimental years. However, in the organic farming system, pea increased significantly in PN and TFPY compared to faba bean as a preceding crop, while in the conventional system, there was no significant difference between the two legumes. The greater yield performance with the two legumes as preceding crops was associated with higher soil NO3-N and total-N concentrations at the beginning of the subsequent faba bean crop. The higher soil N availability when the preceding crop was a legume resulted partly from the higher biomass of crop residues left by these crops on the field after harvest, compared to cabbage. However, it was also associated with a more extensive nodulation of the faba bean roots by rhizobia and a higher percentage of N derived from atmosphere (%Ndfa) in their plant tissues, as determined through the natural abundance of the 15N isotope, when the preceding crop was a legume. The cropping system had no impact on pod yield, but organic farming increased the %Ndfa in both years.

Evaluation of the incidence of endophytic fungi in leaves, stems and roots of bean plants in the State of Paraná

The present study aimed to isolate endophilic fungi from plant tissues (leaves, stems and roots) of beans, in addition to identifying them at the genus level. The experiment was conducted at IDR-Londrina. Bean samples were collected at the Londrina Research Station and at UENP-Bandeirantes. The leaves, stems and roots were separated, fragments of 5 mm diameter were cut and disinfested. They were later transferred to BDA culture medium. The plates were incubated at room temperature for seven days for growth of the microorganisms present. The presence and absence, colonization rate (TC) for each tissue and gender identification of fungi were evaluated. The experiment was conducted in a completely randomized design, with five replications. Forty-eight endophilic isolates were found, 13 in root, 17 in stem and 18 in leaf. CT ranged from 17-100% (leaf), 17-83% (stem) and 16-100% (root). The genus Alternaria sp. and Cladosporium sp. have greater specificity with the leaf and stem, Penicillium sp. root and stem. The genera Fusarium sp. and Aspergillus sp. are found in all organs, Curvularia sp., Nigrospora sp. and Thichoderma sp. demonstrated leaf specificity, Macrophomina sp. the root, and Colletotrichum sp. to the stem. Thus, the identified fungi present potential for future studies in their application in the biocontrol of various plant diseases.

SELEKSI Seleksi Dan Identifikasi Bakteri Penambat Nitrogen Pada Perakaran Tanaman Kacang Hijau (Vigna radiata L) Dan Tomat (Solanum lycopersicum L) Di Kabupaten Belu

Nitrogen fixing bacteria are often called diazotroph bacteria which are able to use air nitrogen as a nitrogen source for their growth. Nitrogen fixing bacteria have the ability to increase the efficiency of N- available in the soil. The purpose of this study was to determine the morphological and biochemical characters of nitrogen-fixing bacteria from the roots of mung bean and tomato plants in Belu Regency. Isolation of nitrogen fixing bacteria by scratch method and spread on NA media. While the selection of nitrogen fixing bacteria using Jensen agar media. The results of the isolation obtained 12 isolates. Six isolates from roots of tomato plants and six isolates from roots of mung bean plants. The morphological characters of the 12 isolates were generally round in shape, small in size, flat in elevation and milky white in color. The selection results showed that 3 isolates grew on Jansen agar media, namely RKHB05, RKHB06, and RTB06. The result of gram staining showed that RKHB05, RKHB06 isolates were gram negative and had cocci cell form, while RTB06 isolates were gram positive with bacillus cell forms. The 3 isolates were positive for motility test, Citrate test, TSIA, and Catalase test

Effect of Rhizobium Inoculation on Growth of Common Bean in Low-Fertility Tropical Soil Amended with Phosphorus and Lime

The cultivation of grain legumes (e.g., common bean) in sub-Saharan Africa contributes to the provision of food for a growing population and delivers environmental benefits such as inputs of nitrogen (N) to crops and soil via symbiotic nitrogen fixation (SNF). However, the success of SNF is constrained by several factors such as the poor efficiency of native rhizobial strains to fix N, the low availability of phosphorus (P) and the acidity of soils. Two trials have been conducted in low-fertility tropical soils at the smallholder farm scale in Madagascar to assess the effects of Rhizobium inoculation together with inputs of P and lime on the growth of the common bean. We showed that inoculation with native strains of Rhizobium had significant effects on bean root nodulation, which was increased by up to 15-fold on plant growth, which increased by 78% and on bean yield, which increased by 126%. Moreover, we observed positive and significant relationships between inoculation with Rhizobium and P fertilization on nodulation, plant growth and yield. However, the addition of dolomite lime did not show any effect in our study. The addition of P decreased the mycorrhization rate of roots. Additional research is still needed to improve our understanding of soil fertility conditions (mainly on nutrient availability, including micronutrients) allowing better efficiency of legume symbionts (rhizobium and mycorrhiza) in such low-fertility soils.

First report of Heterodera glycines infecting commercial dry beans (Phaseolus vulgaris) in Canada

Edible bean is an important human protein source, and Canada is the fifth largest exporter worldwide. Soybean cyst nematode (SCN; Heterodera glycines Ichinohe) is a key soybean ( Glycine max L.) pest, though it also infects dry beans ( Phaseolus spp.). Cysts were observed on black bean roots in a commercial field in Bruce County, Ontario, in August 2018. Based on morphological characteristics, molecular evidence and pathogenicity experiments, SCN was confirmed. This is the first report of naturally occurring SCN infection associated with visible plant damage in a commercial dry bean field in Canada, which is a potential threat to this important niche industry.

ARBUSCULAR MYCORRHIZA SYMBIOSIS REDUCES THE RHIZOCTONIA ROOT ROT AND ALTERS THE PHENOLIC PROFILE IN COMMON BEAN

Arbuscular mycorrhizal fungi (AMF) have the potential to reduce the deleterious effect of soil-borne pathogens, but their ability for pathogen biocontrol may vary depending on the genotype of the plant, the pathogen, and the AMF interaction. Thus, the aim of this work was to evaluate the effect of the Mexican biofertilizer Rizofermic-UV based on a mix of AMF formulation against the common bean root rot caused by the pathogenic fungus Rhizoctonia solani Kühn 1858 (Teleomorph: Thanatephorus cucumeris). Additionally, the total phenolic content, individual phenolic acid (caffeic, ferulic, o-cumaric, p-cumaric, sinapic, and vanillic), and the flavonoid (catechin, kaempferol, quercetin and, rutin) profiles were analyzed. Our results show that the AMF biofertilization reduces the disease severity up to 68 %, and this was accompanied by a boost in total phenolic content in dual inoculation. Furthermore, a variation in the individual phenolic profiles caused by both AMF interaction and pathogen treatment alone were observed. In dual inoculations, vanillic acid was significantly different among treatments, suggesting it may contribute to the enhanced resistance of mycorrhizal roots to soil-borne pathogens. Further work is required to elucidate the exact role of these compounds in the bioprotection of arbuscular mycorrhizal to plant pathogens.

Phytochemical screening of extracts cotton plants (Gossypium Barbadense), pumpkin plants (Cucurbita Pepo) and valavet bean (Mucuna Pruriens) in Fufore Local government of Adamawa State, Nigeria

Alkaloids, saponins, anthraquinones, glycosides, phenolics, terpenoids and flavonoids distribution in ten medicinal plants belonging to different families were assessed and compared. The medicinal plants investigated were cotton (Gossypium hursitum), Cucurbita pepo (Pumpkin) and velvet bean (Mucuna prupriens). The results of the phytochemical analysis showed the presence of major classes of secondary metabolites such as alkaloids, tannins, saponins, flavonoids, glycosides, phytosterols, carbohydrates, proteins, terpenoids and anthraquinones in ethanolic and aqueous extract. The results of cotton (Gossypium hursitum) leaves and roots in ethanolic extract revealed the presence of alkaloids, tannins, saponins, flavonoids, glycosides, phytosterols, carbohydrates, proteins, and anthraquinones. Terpenoids were absent in the leaves of cotton (Gossypium hursitum), meanwhile Glycosides were absent the roots of cotton (Gossypium hursitum) in ethanolic extracts. The result of aqueous extracts of cotton (Gossypium hursitum) leaves and roots showed the presence of alkaloids, tannins, saponins, flavonoids, glycosides, phytosterols, carbohydrates, proteins, terpenoids and anthraquinones. While the roots revealed the absence of protein and terpenoids. Similarly, the Phytochemical screening result of Cucurbita pepo (Pumpkin) leaves and roots of ethanolic and aqueous extracts revealed the presence of some bioactive components in the extracts such as alkaloids, tannins, phytosterols, carbohydrates, proteins and anthraquinones. Whereas saponins, flavonoids, glycosides, terpenoids were absent in the ethanolic extracts of Cucurbita pepo (Pumpkin) leaves. And also, saponins, glycosides and terpenoids were absent in the roots of Cucurbita pepo (Pumpkin). While the aqueous extract of the leaves revealed all the phytochemical being carried out except saponins, flavonoids and Terpenoids are absent. Also, the aqueous extracts of Cucurbita pepo (Pumpkin) roots revealed the presence of some secondary metabolites as shown in table IV such as alkaloids, tannins, flavonoids, phytosterols, carbohydrates, proteins, terpenoids and anthraquinones. Saponins and glycosides were absent. The results of the velvet bean (Mucuna prupriens) leaves and roots of ethanolic extract showed that alkaloids, saponins, phytosterols, carbohydrates, proteins, terpenoids and anthraquinones were present both in leaves and roots with tannins present only in the roots. However, flavonoids, glycosides, were absent in both leaves and roots of velvet bean (Mucuna prupriens). The result of aqueous extract of velvet bean (Mucuna prupriens) leaves and roots revealed the presence of alkaloids, saponins, flavonoids, phytosterols, carbohydrates, proteins, terpenoids and anthraquinones while tannins, glycosides were found absent. Similarly, the aqueous roots extract revealed all the phytochemical tested except flavonoids, terpenoids were absent in the roots of velvet bean (Mucuna prupriens). Results of this study may provide a foundation for designing new drugs for several diseases.

Foliar Spray of Biosynthesized Zinc Oxide Nanoparticles Alleviate Salinity Stress Effect on Vicia faba Plants

Previous studies recorded positive impact of ZnO NPs on plants stressed with salinity. The current work was performed to study the effect of two different concentrations of biosynthesized ZnO NPs (50 and 100 mg L−1) on faba bean plants under salinity stress. The zinc oxide nanoparticles (ZnO NPs) were synthesized using Mentha extract, and their shape and size were characterized using X-ray diffraction and transmission electron microscope while diffuse reflectance spectra were measured using UV–Vis spectrophotometer. The generated ZnO NPs were spherical with a particle size 9.4 nm and had a rod form with particle size 15.2 in length and 3.5 nm in width. The response of faba been plants to the foliar spray of ZnO NPs concentrations (0, 50, and 100 mg L−1) alone and in combination with salt stress at 150 mM NaCl was studied. Salinity induced reduction in faba bean root and shoot length and dry/fresh weights, while an enhancement was recorded in response to foliar treatment with ZnO NPs at 50 and 100 mg L−1 either in presence or absence of salinity stress. The highest amounts of chlorophyll a, b, carotenoids, and total pigments were recorded in plants received 50 mg L−1 ZnO NPs compared to the alternative control. Secondary metabolites (phenols, flavonoids, and tannins) were accumulated in salinity-stressed plants and further accumulation in response to ZnO NPs treatment was noticed. Amino acids, proline, glycine betaine, and total soluble sugars, as well as enzymatic and non-enzymatic antioxidant contents, increased almost onefold in salinity-stressed plants as compared to control plants while the 50 mg L−1 ZnO NPs treatment resulted in higher accumulation of the previously mentioned substances. In contrast, plants oxidative stress was reduced in response to ZnO NPs treatments. The nitrogen, phosphorus, potassium, calcium, zinc, and iron contents of faba bean plants were recorded under salinity stress and in response to the two applied concentrations of ZnO NPs. Faba bean plants stressed with 150 MN NaCl showed growth decline that may be attributed to osmotic stress and low water availability imposed by salinity. The treatment of stressed plants with 50 mg L−1 ZnO NPs induced an enhancement in plant growth as well as an accumulation of antioxidants, osmolytes, and secondary metabolites that could help plants overcome the negative effects of salinity.

Influence of common bean genotypes and rhizobia interaction for nodulation and nitrogen fixation

Bacteria from the rhizobia group are able to associate symbiotically with bean crop, forming nodules in the root, in which the biological nitrogen-fixing process occurs. However, the efficiency of this process has been low and it can be attributed to genetic and environmental factors. Thus, the objective of this study was to evaluate the capacity of nodulation of local varieties and commercial common bean cultivars inoculated with a Rhizobium tropici strain used in commercial inoculants and rhizobia isolates from common bean root nodules. The experiment was carried out in a factorial scheme (2x4), in a randomized block design with four replicates. It was tested two local varieties and two commercial cultivars, inoculated with the reference Rhizobium tropici strain CIAT899 and the RBZ14 strain isolated from common bean nodules grown in soils of Southern Brazil, in adapted Leonard-type pots. The CIAT899 strain promoted either higher mass of viable nodules and higher nitrogen accumulation in the aerial part. The black group local variety showed better response than the cultivar TAA Dama for nodule viability, suggesting more efficiency for nodulation. The interaction between genotypes (local varieties and commercial cultivars) and bacteria showed the specificity of the complex symbiotic relationship of biological nitrogen fixation in common bean, requiring further studies of these interactions.

Critical Limits for Soybean and Black Bean Root Growth, Based on Macroporosity and Penetrability, for Soils with Distinct Texture and Management Systems

Soil compaction is a worldwide problem in agricultural areas, and it is important to define soil properties and reference values that allow knowledge of the compaction level for decision making. The objective of this study was to define the critical values of physical properties associated with the compaction of soils. Three Ultisols and two Oxisols, under different management systems, were collected at different depths for an evaluation of particle size, volumetric moisture, bulk density, and porosity. In the field, soil resistance to penetration and the root length of the soybean and edible black bean crop were measured. The soil profiles presented horizontal layers with similar resistance, but in some cases, there is discontinuity of these layers, which allows the roots to use the zones of lower resistance to deepen in the profile. The values of bulk density and resistance to penetration critical to soybean and edible black bean (only in sandy loam soil) root growth, according to soil textural class, are: sandy loam = 1.66 Mg m−3 and 1.5 to 2 MPa; loam and clay loam = 1.52 Mg m−3 and 1 to 1.5 MPa; silty clay loam and silty clay = 1.32 Mg m−3 and 1.5 to 2 MPa; and clay = 1.33 to 1.36 Mg m−3 and 2 to 3.5 MPa.

Culturable Bacterial Endophytes Associated With Shrubs Growing Along the Draw-Down Zone of Lake Bogoria, Kenya: Assessment of Antifungal Potential Against Fusarium solani and Induction of Bean Root Rot Protection.

Vascular shrubs growing along the draw-down zones of saline lakes must develop adaptive mechanisms to cope with high salinity, erratic environmental conditions, and other biotic and abiotic stresses. Microbial endophytes from plants growing in these unique environments harbor diverse metabolic and genetic profiles that play an important role in plant growth, health, and survival under stressful conditions. A variety of bacterial endophytes have been isolated from salt tolerant plants but their potential applications in agriculture have not been fully explored. To further address this gap, the present study sought to isolate culturable bacterial endophytes from shrubs growing along the draw-down zone of Lake Bogoria, a saline alkaline lake, and examined their functional characteristics and potential in the biocontrol of the bean root rot pathogen, Fusarium solani. We collected shrubs growing within 5 m distance from the shoreline of Lake Bogoria and isolated 69 bacterial endophytes. The endophytic bacteria were affiliated to three different phyla (Firmicutes, Proteobacteria, and Actinobacteria) with a bias in the genera, Bacillus, and they showed no tissue or plant specificity. All selected isolates were positive for catalase enzyme grown in 1.5 M NaCl; three isolates (B23, B19, and B53) produced indole acetic acid (IAA) and only one isolate, B23 did not solubilize phosphate on Pikovskaya agar. Isolates, B19 and B53 exhibited more than 50% of mycelial inhibition in the dual culture assay and completely inhibited the germination of F. solani spores in co-culture assays while two isolates, B07 and B39 had delayed fungal spore germination after an overnight incubation. All isolates were able to establish endophytic association in the roots, stems, and leaves of been seedlings in both seed soaking and drenching methods. Colonization of bean seedlings by the bacterial endophytes, B19 and B53 resulted in the biocontrol of F. solani in planta, reduced disease severity and incidence, and significantly increased both root and shoot biomass compared to the control. Taxonomic identification using 16S rRNA revealed that the two isolates belong to Enterobacter hormaechei subsp., Xiangfangensis and Bacillus megaterium. Our results demonstrate the potential use of these two isolates in the biocontrol of the bean root rot pathogen, F. solani and plant growth promotion.

Adding intercropped maize and faba bean root residues increases phosphorus bioavailability in a calcareous soil due to organic phosphorus mineralization

Adding intercropped maize and faba bean root residues increases phosphorus bioavailability in a calcareous soil due to organic phosphorus mineralization