Common Bean Crop Research Articles

Enhanced-Efficiency Phosphorous Fertilizer Impacts on Corn and Common Bean Crops and Soil Phosphorus Diffusion

Phosphorus (P) supply to crops is a major constraint on the quantity and quality of food production in tropical soils, which are often characterized by highly weathered soils having low phosphorus use efficiency. Increasing P fertilizer use efficiency is a good tool for increasing food production to feed an increasing world population. Enhanced efficiency P fertilizer is used to achieve this goal. The lack of information about soil P diffusive flux and corn and common bean yield response with increased efficiency P fertilizers justify studies to evaluate the performance of this type of fertilizer. The aims of this study were to evaluate P diffusive flux and corn and common bean crop response to P sources and rates. A laboratory trial was carried out to evaluate soil P diffusive flux in response to P sources (MAP and Policote coated MAP). Field trials were carried out to evaluate corn and common bean yields in response to P sources (MAP and Policote coated MAP) and rates. Policote, an additive based on water-soluble polymers, is an anionic copolymer with iron an aluminum affinity. Increasing contact time between P-fertilizers and soil reduced phosphorus diffusive flux. Policote coated P-fertilizer resulted in higher phosphorus diffusion than conventional phosphorus fertilizer. Phosphorus fertilization increased corn and common bean yields. Policote coated phosphorus fertilizer resulted in higher agronomic P efficiency use, corn, and common bean yields than conventional phosphorus fertilizer. Policote coated P fertilizer can be used as an enhanced efficiency fertilizer and is a more efficient way to deliver required phosphorous to plants. Reducing farm investment, increasing agricultural profits, preserve phosphatic rocks reserves, and avoid the overuse of phosphate fertilizer could be realized through the rational use of enhanced efficiency fertilizers and fertilizer rate use reduction.

Impact of crop management and no-tillage system on grain and straw yield of maize crop

The aim of this study was to evaluate straw production provided by maize and Urochloa ruziziensis grown solely and intercropped, as well as the accumulation of nitrogen and its residual effect when applied as a topdressing fertilizer to the previous crop (common bean) under no-tillage. Experiments were conducted for two crop seasons in a randomized block design, in a split-plot scheme, with four repetitions. We evaluated three cropping systems containing maize and U. ruziziensis solely and intercropped (summer crop) in succession with irrigated common beans (winter–spring crop), managed with nitrogen topdressing combinations with 90 kg N ha−1 by urea. Cropping systems with maize and U. ruziziensis solely or intercropped promoted sufficient straw production under the no-tillage system. Urochloa ruziziensis solely or intercropped with maize achieved full soil surface coverage and higher straw yield (8.3 to 9.5 t ha−1) compared to sole maize (7.1 to 7.8 t ha−1), thus favoring the implementation and maintenance of the no-tillage system. The quality of straw produced in crop succession systems was improved by nitrogen fertilizer applied to the previous common bean crop, which changed their nutrient content and nitrogen accumulation.

Pesticide residues determination in common bean using an optimized QuEChERS approach followed by solvent exchange and GC-MS/MS analysis.

Common bean is a staple food in Latin America and Africa; however, studies about contamination of common bean with pesticides are rarely reported. So, the goals of this study were to validate a multiresidue method and apply it in monitoring of pesticides in common beans. Extraction was performed applying the QuEChERS (quick, easy, cheap, effective, rugged, and safe) approach to ground samples. Octadecylsilane and primary-secondary amine were used for clean-up, and a solvent exchange step was performed before injection for gas chromatography-tandem mass spectrometry analysis. Method validation was done analyzing blank samples spiked at 20, 30, 50, and 100 μg kg-1 (n = 5). Linearity and linear range were assessed by the analysis of standard solutions at concentrations of 5, 15, 25, 50, 75, 100, and 150 μg L-1 . The method was successfully validated for 91 (64.1%) of the 142 compounds studied (139 pesticides and three degradation products). Limits of quantification were equal to 20 μg kg-1 , 30 μg kg-1 , 50 μg kg-1 , and 100 μg kg-1 for 18 (12.7%), 17 (12.0%), 21 (14.8%) and 35 (24.6%) compounds respectively. Fifteen (10.6%) compounds were not detected at any level, and 36 (25.4%) did not fulfill the requirements for a quantitative method. Sixteen common bean samples of South of Brazil were analyzed. Two samples were positive: one for tebuconzole and a second for picoxystrobin, permethrin, and cyproconazole. Cyproconazole is not allowed for use in the common bean crop, its use being a violation. As demonstrated, the validated approach is suitable for pesticide residues determination in common bean. Results of the sample analysis show that the control of pesticide residues in common bean is necessary to ensure food safety. © 2020 Society of Chemical Industry.

Improving African bean productivity in a changing global environment

Common bean (Phaseolus vulgaris) cultivation delivers income to farmers and nutrition to consumers in sub-Saharan Africa. With a growing population and land scarcity, there will be greater pressure to intensify common bean and other crops in the region. However, high temperatures and increased drought may reduce common bean yields in Africa. Climate change impacts on climbing beans are not yet clear. Therefore, the objective of this study was to evaluate the expected impact of climate change on suitability for climbing bean cultivation. The study identifies areas suitable to cultivate climbing beans in sub-Saharan Africa, taking into account the present climate as well as the predicted future climate. The analysis compares and evaluates the performance of two ecological niche models—Ecocrop and MaxEnt—under future climatic conditions, according to global circulation models of the last Intergovernmental Panel on Climate Change (IPCC) report. The Ecocrop model results showed a wide common bean distribution in comparison with those of MaxEnt, which showed a better approximation to the current distribution of climbing beans. The MaxEnt model performed well as judged by validation statistics and comparison with climbing bean production data. Overall, the models project climate change to decrease the suitability of climbing beans in Africa. The results suggest that rising temperatures and variable rainfall will most severely affect bean production in countries of southern Africa such as Zambia, Zimbabwe, Malawi, and Mozambique. In other parts of the tropics, climbing bean cultivation may suffer rising temperatures and more variable rainfall at higher latitudes, as opposed to areas near the equator. The study suggests where agricultural specialists can promote climbing beans in Africa and other regions of the world, where they are highly suitable and not yet widely cultivated. Researchers can improve studies such as this one for beans and other crops by developing more detailed calibration and validation data sets for modeling efforts.

Hydrogen-uptake genes improve symbiotic efficiency in common beans (Phaseolus vulgaris L.).

Hydrogen-uptake (Hup) activity is implicated in the mitigation of energy losses associated with the biological nitrogen fixation process, and has been related to productivity increases in some legume hosts. However, in common bean (Phaseolus vulgaris L.) the expression of hydrogenase is rare. In this study an 18-kb hup gene cluster from Rhizobium leguminosarum bv. viciae encoding a NiFe hydrogenase was successfully transferred to three common bean rhizobial strains lacking hydrogenase activity (Hup-) but symbiotically very effective and used in commercial inoculants in Brazil: one strain originally from Colombia (Rhizobium tropici CIAT 899), and two strains from Brazil (R. tropici H 12 and Rhizobium freirei PRF 81). The inclusion of NiCl2 in the nutrient solution did not increase hydrogenase activity, indicating that common bean plants allow efficient nickel provision for hydrogenase synthesis in the bacteroids. The symbiotic performance-evaluated by nodulation, plant growth, N accumulation and seed production-of wild-type and Hup+ derivative strains was compared in experiments performed with cultivar Carioca under greenhouse conditions, in sterile substrate and in non-sterile soil. Statistically significant increases in one or more parameters were observed for all three Hup+ derivatives when compared to the respective wild-type strain. Differences were found mainly with the Brazilian strains, reaching impressive increases in nodule efficiency and seed total N content. The results highlight the potential of using Rhizobium Hup+ strains for the design of more energy-efficient inoculants for the common bean crop.

Soil water availability for drip-irrigated common bean crop

ABSTRACT Minimum limits of soil water storage should be established for the irrigation management of crops, in order to satisfactorily provide water to plants. This study aimed to define the soil water availability factor (f factor) that provides the maximum agronomic yield and maximum water-use efficiency for drip-irrigated common bean cultivars. The experiment was carried out in a randomized block design, with four replications. The treatments were arranged in split plots, with the plots consisting of f factors (0.20, 0.35, 0.50, 0.65 and 0.80) and subplots consisting of common bean cultivars (BRS Pérola and BRS Estilo). The use of f factors between 0.30 and 0.35 is recommended for common bean crops to obtain the maximum agronomic yield and maximum water-use efficiency. The BRS Estilo cultivar presents a water-use efficiency 16 % higher than the BRS Pérola.

IAC Netuno: A new black bean cultivar resistant to anthracnose and Fusarium wilt

IAC Netuno, a black common bean cultivar with high grain yield potential, 2968.20 kg ha-¹, upright plant architecture and Type II indeterminate growth habit, about a 90-day cycle, and 1000-seed weight of 230 grams, recommended for all common bean crop seasons in the state of São Paulo.

Reprodução dos nemátodes das galhas radiculares, Meloidogyne ethiopica e Meloidogyne luci, em cultivares de feijoeiro

The productivity of common bean crop is limited by several biotic factors, being often affected by plant-parasitic nematodes. Several species of root-knot nematodes (RKN), Meloidogyne spp. have been reported as damaging to the crop. Recently, Meloidogyne luci and M. ethiopica were recorded parasitizing roots of common bean plants in Brazil. Therefore, the objective of this work was to evaluate the reproduction of M. ethiopica and M. luci on twenty bean cultivars. Plants were inoculated with 5,000 eggs plus second stage juveniles (J2) of RKN and pots were maintained in a greenhouse. Sixty days after inoculation, the roots of each plant were evaluated for number of galls, final population and reproduction factor (RF = final population / initial population) and the means of the different variables were compared by the Scott and Knott grouping test at 5%. Results showed that all tested cultivars were susceptible to both RKN, with RF ranging from 9,8 to 55,9 for M. ethiopica and from 6.0 to 20.0 for M. luci.

Effects of organomineral fertilizers formulated with biosolids and filter cake on common bean yield crop (Phaseolus vulgaris L.)

The objective of this research was to evaluate the efficiency of different sources of residues in the composition of organomineral fertilizers on common bean yield. The experiment was carried out in a greenhouse at the Federal University of Uberlândia. A randomized complete block design was used in the 2 x 4 + 2 factorial scheme corresponding to two organic sources (biosolids and filter cake) and four doses of pelletized organomineral fertilizer (50, 75, 100 and 125% of the recommendation for common bean, plus two additional treatments without fertilization and fertilization with mineral fertilizer). The plant height and stem diameter were evaluated at 30 days after sowing (DAS), and an average number of pods plant-1 and grains pod-1, yield (g plant-1), dry mass (g), and mass of 1000 grains (g) at 84 DAS. The organomineral fertilizer based on biosolids fertilizer provides the largest growth with the use of 100% of the recommended dose, the largest volume of dry mass up to 75% and the highest yield at 50%. The organomineral fertilizer based on filter cake increased dry mass volume. The organomineral fertilizers evaluated have the potential to substitute exclusively mineral fertilization in the common bean crop.

Biostimulants action in common bean crop submitted to water deficit

The water deficit (WD) is one of the severe problems in agriculture resulting in yield loss. The understating of crops behavior face to this condition becomes of great importance, and the use of biostimulants may act as a vegetal growth-promoting, considering its capacity of attenuate the impacts of WD on plants. This study aimed at evaluating the common bean changes in biometric parameters and its yield supplemented with biostimulants, as a response to the imposition of WD. The assay was conducted in a protected environment in Botucatu, Brazil, with common bean cv. IAC Imperador, disposed in split-plot in randomized blocks, with 4 repetitions. The treatments in the plots correspond to the irrigation depths (10 kPa and 40 kPa) and in the subplots the treatment B1 (control); B2 (Bacillus amyloliquefaciens BV 03) and B3 (Bacillus amyloliquefaciens BV 03 + brown algae extract – Ascophyllum nodosum). The irrigation was by drip and the management using a tensiometer. The biometric variables included stem diameter; leaf number and leaf area; leaf dry mass, stem, root and total; root length, diameter and volume; and yield parameters. Discussing the results, it was possible to conclude that the common bean is a very water dependable crop, with WD imposition interfering in all the studied variables, with growth decrease, biomass accumulation and yield. The applied biostimulants (B2 and B3) presented low capacity to attenuate the WD effects in common bean under the cultivation conditions adopted.

Combining Ability for Agromorphological and Physiological Traits in Different Gene Pools of Common Bean Subjected to Water Deficit

Water stress is one of the main limiting factors for common bean crops, negatively affecting grain yield and seed quality. Thus, the objective of this study was to evaluate the inheritance of agromorphological and physiological traits related to drought tolerance in order to identify promising combinations. The experiment was carried out in a greenhouse with a partial diallel scheme between three drought-tolerant genotypes (IAPAR 81, BAT 477. and SEA 5), and nine cultivars widely grown in Brazil (BRS Estilo, IAC Alvorada, IPR Campos Gerais, IPR Uirapuru, IPR Nhambu, BRS Esteio, IPR Garça, BRS Radiante, and DRK 18), in a randomized block design with four replicates. The plants were grown in pots with substrate under 80% of pot capacity until they reached the stage R5, when water supply was restricted to 30% for 20 days in the pots under stress treatment. A wide variability for the agromorphological and physiological traits was observed. Water deficit reduced plant performance for most agromorphological traits and altered their physiological metabolism. Additive and non-additive effects are involved in the genetic control of the majority of agromorphological and physiological traits both under water stress and control (well-watered) conditions. The parental genotypes BAT 477 (group I) and IAC Alvorada, IPR Uirapuru, and BRS Esteio (group II) may be included in breeding programs aiming at improving drought tolerance in common bean since they present high positive general combining abilities for agromorphological traits. The crosses IAPAR 81 × IPR Campos Gerais, and SEA 5 × BRS Radiante resulted in the best combinations considering grain yield per plant and total dry biomass, when cultivated under water deficit.

Application of controlled-release nitrogen fertilizer in irrigated common bean crops

The use of adequate management practices and high nitrogen fertilizer rates have contributed to increase the common bean grain yield, however, the application of nitrogen fertilizer at sowing still requires evaluations for irrigated crops in the Brazilian Cerrado biome region. Thus, the objective of this work was to evaluate the effect of application of different rates of controlled-release nitrogen fertilizer—dimethylpyrazole phosphate (DMPP)—at sowing and as top-dressing on agronomic performance and leaf area index of irrigated common bean crops grown in the Brazilian Cerrado biome region. A randomized block design in a 4×3 factorial arrangement with four replications was used. The treatments consisted of four nitrogen rates (0, 60, 120, and 180 kg ha-1) and three application forms (100% at sowing, 100% as top-dressing, and 50% at sowing + 50% as top-dressing). Irrigation was managed with class A tanks and two-day intervals. The nitrogen applied at the different stages of the crop did not affect the production components of the common bean plants. The highest grain yields were found with the nitrogen rates of 180 kg ha-1 in 2015 (1,756.37 kg ha-1), and 123.98 kg ha-1 in 2016 (1,799.63 kg ha-1).

Detection of potyviruses infecting Iranian common beans using broad-spectrum antibodies and universal primer pairs

Six provinces of Iran were surveyed during 2012–2014 to detect potyviruses infecting common bean crops. A total of 277 leaf samples were collected from bean plants and some other legumes as well as weeds and wild legumes showing virus-like symptoms. Enzyme-linked immunosorbent assay (ELISA) using broad-spectrum potyvirus antibodies gave a positive reaction with 63 samples (22.7%). Moreover, a mixed colony of aphids (Aphis craccivora and A. fabae), collected from a locust tree plant (Robinia sp.), transmitted a potyvirus to young healthy bean plants; the infection was confirmed through serological assays. Partial nuclear inclusion b (NIb) and coat protein (CP) regions of the genomes of 19 ELISA-positive samples were amplified by reverse-transcription polymerase chain reaction (RT-PCR) using NIb and NWCIEN (or WCIEN) universal primer sets, respectively. Potyvirus species identification was confirmed by BLASTN and phylogenetic analyses followed by ELISA tests using virus-specific antibodies or biological assays. The results clearly showed the presence of Bean common mosaic virus (BCMV), Bean common mosaic necrosis virus (BCMNV), Bean yellow mosaic virus (BYMV) and Wisteria vein mosaic virus (WVMV) in the samples tested. Non-specific amplification of a Cucumovirus genome by using NIb primers was also recorded. The results showed the natural occurrence of a new potyvirus species (WVMV), and a new host for BYMV (Trifolium repens) in the mid-Eurasian region of Iran. Our findings indicate the capacity of the universal detection systems for fast and accurate detection of legume potyviruses in the country and for use in routine diagnostic assays.

Artificial Defoliation to Simulate Losses on Production of Bean (<i>Phaseolus vulgaris</i> L. cv. Goytacazes)

The reduction of foliar area can cause yield reduction in common bean crops. The objective of this work was to verify which is the effect of different defoliation levels realized in several development stages of common bean (Phaseolus vulgaris L. cv. Goytacazes) over yield, weight of 100 seeds and number of pods per plant. The experimental design was randomized blocks, in a split-plot arrangement with five replications. The plot corresponded to the five defoliation epochs (first trifoliate leaf, flowering, pods formation, pods filling, and dry pods). In each plot, the split plot was represented by the four defoliation levels (0%, 33%, 67% and 100%). It was observed a decrease of yield for all levels defoliation considering all development stages, except for dried pods. The highest decrease was detected for flowering and pods formation. Through the regression analysis got a greater reduction in yield with 100% defoliation made at 42 days after emergence. The evaluation parameter that showed better relation with yield was a number of pods per plant.

A Novel Strain of Pepper Leafroll Virus Infecting Common Bean and Soybean in Ecuador

Symptoms resembling those caused by begomoviruses (Geminiviridae: Begomovirus) have been observed in common bean and other leguminous crops in Ecuador in the last few years. The only begomovirus species found infecting legumes (common bean and cowpea) in the country to date is cabbage leaf curl virus (CabLCV) (Fiallo-Olive et al. 2018). During May to June 2017, a survey of leguminous plants was conducted in the Ecuadorian localities of Santa Elena (Santa Elena province), Milagro (Guayas province), and Pallatanga (Chimborazo province). Twenty-four plants showing leaf deformation and/or mosaic symptoms were sampled, including common bean (Phaseolus vulgaris, n = 21), soybean (Glycine max, n = 2), and pigeon pea (Cajanus cajan, n = 1). Most common bean plants were infested with whiteflies (Hemiptera: Aleyrodidae) that were also collected. Total DNA was extracted from leaf samples and used as template in polymerase chain reaction (PCR) using specific primers for CabLCV (MA2540 [5′-GATGTTGAAGCATCTGCAAACATTC-3′] and MA2541 [5′-CTAGGAACATCAGGGCTTCTCAAC-3′]) (Fiallo-Olive et al. 2018). All samples were negative for the presence of CabLCV. DNA extracts were then used as templates in rolling-circle amplification (RCA) using φ29 DNA polymerase (TempliPhi kit, GE Healthcare). Digestion of RCA products with a set of restriction enzymes yielded identical restriction patterns for six samples (five common bean and one soybean), suggesting the presence of a bipartite begomovirus. BamHI and NcoI fragments of approximately 2.6 kbp from a common bean plant were cloned in pBluescript II SK(+), and two selected clones were sequenced (Macrogen, Seoul, South Korea). BLAST analysis showed that the clones corresponded to begomoviral DNA-A (BamHI, 2,580 nt, GenBank accession no. MH481901) and DNA-B (NcoI, 2,561 nt, MH481902). Pairwise identity scores with isolates selected after BLAST analysis were calculated with SDT (Muhire et al. 2014). Cloned DNA-A and DNA-B showed the highest identity (93 and 92%, respectively) with pepper leafroll virus (PepLRV) (KC769819 and KC769820), a bipartite begomovirus identified infecting pepper, common bean, and tomato in Peru (Martinez-Ayala et al. 2014). To confirm the identity of the begomovirus present in the rest of the samples, PCR was performed with specific primers whose design was based on the cloned PepLRV DNA-A (MA2602 [5′-GTTAATGGACAATGAGGGTATGTG-3′] and MA2603 [5′-CACGAGGAGAATAATTGGCGTTAC-3′]) using Taq DNA polymerase (BIOTAQ, Bioline) and thermocycler conditions consisting of 35 cycles with 45 s annealing steps at 57°C. DNA fragments of the expected size (452 bp) were amplified from the six samples, and direct sequencing showed them to be identical to the cloned PepLRV DNA-A, supporting the presence of this virus. Based on the species/strain demarcation threshold for the viruses in the genus Begomovirus (Brown et al. 2015), the isolate characterized here belongs to a new strain of PepLRV. DNA was extracted from individual whiteflies (n = 42) using a Chelex-based method, and PCR was carried out using mitochondrial cytochrome oxidase I gene primers, C1-J-2195 (5′-TTGATTTTTTGGTCATCCAGAAGT-3′) and Btab-uni-PrimerR (5′-CTTAAATTTACTGCACTTTCTGCCAYATTAG-3′). Direct sequencing of PCR products showed that seven sequences (one deposited in GenBank with accession no. MH481903) were identical to numerous sequences of Bemisia tabaci Middle East-Asia Minor 1 (MEAM1, formerly B biotype), known to be an efficient vector of begomoviruses. To our knowledge, this is the first report of PepLRV in Ecuador and of soybean as a host for the virus, which had been identified only in Peru to date. Also, this is the first molecular evidence of the presence of B. tabaci MEAM1 in the country.

Foliar and topdressing application of nitrogen to the common bean crop

Abstract: The objective of this work was to evaluate the effect of applying N sources to leaves and N rates to the soil on the growth, N uptake, and grain and crude protein yields of the common bean (Phaseolus vulgaris) crop. Three experiments - two irrigated and one rainfed - were conducted during the 2012/2013 agricultural season, in a randomized complete block design with four replicates. The treatments consisted of the application of: four N rates (0, 45, 90, and 180 kg ha-1) to the soil, as topdressing in the V4 stage; and five N sources/rates - i.e., control, without foliar N application; 2.5 kg ha-1 N as conventional urea (N-CU); 5.0 kg ha-1 N-CU; 2.5 kg ha-1 N as slow-release urea-formaldehyde (N-SR); and 5.0 kg ha-1 N-SR - to leaves, in the R5 stage. Soil N fertilization, using rates between 124 and 180 kg ha-1, increases shoot N content and uptake, number of pods per plant, grain yield, and protein content and yield. Regardless of the growing environment and N application to the soil, the foliar supply of N as slow-release urea-formaldehyde increases grain and protein yields, whereas the greatest rate of N as conventional urea also increases grain yield.

Impact of climate change on climatic zoning of common bean in the South of Brazil

The common bean ( Phaseolus vulgaris L.) is a crop of high economic and social importance in Brazil. The objective of this study is to determine the impacts of climate change on climatic zoning, i.e., to define aptitude classes for cultivation and the periods recommended for the sowing times of the common bean in rainfed conditions for the period 2071 to 2100 in the states of Parana, Santa Catarina and Rio Grande do Sul, in the south of Brazil. Three climate scenarios were used to evaluate the potential impact of climate change on climatic zoning of the common bean crop: current (baseline - 1961-1990) and predicted future climatic conditions (2071-2100) (A2 and B2). The climatic zoning for the three scenarios (current, A2 and B2) were elaborated with the following aptitude classes: suitable and unsuitable for crop cultivation. Suitable for cultivation of common bean crop was considered when at least one 10 day period was indicated for sowing time. In the south of Brazil there is a spatial and temporal change of area suitable for cultivation and recommended sowing time by climatic zoning for the common bean crop in the future scenarios, both optimistic (B2) and pessimistic (A2).

Photosynthetic Potential and Productivity of Common Beans under Herbicide Effect

ABSTRACT: The objective of this study was to evaluate the effects of the application of contact herbicides recommended for common bean crops, as for chlorophyll a fluorescence parameters, leaf soluble proteins content (LSPC) and productivity. The experiment was conducted on the field with five treatments, which were the application of the following herbicides: bentazon (720 g ha-1), fluazifop-p-butil (187.5 g ha-1), fomesafen (250 g ha-1) fluazifop-p-butil + fomesafen (187.5 + 250 g ha-1), and a manually weeded control treatment without herbicide application, in a randomized block design with four replications. Bentazon was the only herbicide causing significant reductions, but only until the first day after herbicide application (DAA), on the following chlorophyll a fluorescence parameters: maximum quantum yield of photosystem II (Fv/Fm), effective quantum yield of photosystem II (ϕPSII), photochemical quenching (qP); it also induced an increase in non-photochemical quenching (NPQ). Fv/Fm was the best parameter to indicate herbicide effect on the photosynthetic apparatus of plants in the field. Chlorophyll a fluorescence parameters obtained in light-adapted leaves underwent a high environmental influence, especially deriving from the variation in the photosynthetic photon flow density (PPFD) during measurements; they are not recommended to evaluate the effects of herbicides on the field. None of the applied herbicides evaluated caused reductions in grain yield; therefore, they are recommended for common bean crops.

Rhizobium strains in the biological control of the phytopathogenic fungi Sclerotium (Athelia) rolfsii on the common bean

To identify Rhizobium strains’ ability to biocontrol Sclerotium rolfsii, a fungus that causes serious damage to the common bean and other important crops, 78 previously isolated rhizobia from common bean were assessed. Dual cultures, volatiles, indole-acetic acid (IAA), siderophore production and 16S rRNA sequencing were employed to select strains for pot and field experiments. Thirty-three antagonistic strains were detected in dual cultures, 16 of which were able to inhibit ≥84% fungus mycelial growth. Antagonistic strains produced up to 36.5 μg mL−1 of IAA, and a direct correlation was verified between IAA production and mycelium inhibition. SEMIA 460 inhibited 45% of mycelial growth through volatile compounds. 16S rRNA sequences confirmed strains as Rhizobium species. In pot condition, common bean plants grown on S. rolfsii-infested soil and inoculated with SEMIA 4032, 4077, 4088, 4080, 4085, or 439 presented less or no disease symptoms. The most efficient strains under field conditions, SEMIA 439 and 4088, decreased disease incidence by 18.3 and 14.5% of the S. rolfsii-infested control. Rhizobium strains could be strong antagonists towards S. rolfsii growth. SEMIA 4032, 4077, 4088, 4080, 4085, and 439 are effective in the biological control of the collar rot of the common bean.

Economically optimal water depth and grain yield of common bean subjected to different irrigation depths

ABSTRACT Common bean crop plays an important role in the world, not only in economic aspects but also in social development. The objective of this study was to evaluate the grain yield and the economically optimal water depth which reflects the maximum technical efficiency of the common bean crop. The experiment was conducted in greenhouse, in Alegrete - RS, from February to May 2016. A completely randomized design was used, consisting of five water replacement treatments (25, 50, 75, 100 and 125% crop evapotranspiration - ETc) and four replicates. Based on the obtained results, both water deficit and water excess directly affected the final grain yield of the crop. Maximum grain yield was 3,554.1 kg ha-1, obtained by applying 492.72 mm (100% ETc). On the other hand, the economically optimal water depth was estimated at 91.2% ETc, indicating that water depths above this value are not suitable for maximum technical efficiency in the common bean crop under these conditions. It was concluded that the water depth equivalent to 100% ETc maximizes grain yield for the region of Alegrete-RS, and irrigation is considered a solution in the water supply to the common bean crop during critical periods.