Common Bean Production Research Articles

Next-Generation Sequencing-Based Detection of Common Bean Viruses in Wild Plants from Tanzania and Their Mechanical Transmission to Common Bean Plants.

Viral diseases are a major threat for common bean production. According to recent surveys, >15 different viruses belonging to 11 genera were shown to infect common bean (Phaseolus vulgaris L.) in Tanzania. Virus management requires an understanding of how viruses survive from one season to the next. During this study, we explored the possibility that alternative host plants have a central role in the survival of common bean viruses. We used next-generation sequencing (NGS) techniques to sequence virus-derived small interfering RNAs together with conventional reverse-transcription PCRs (RT-PCRs) to detect viruses in wild plants. Leaf samples for RNA extraction and NGS were collected from 1,430 wild plants around and within common bean fields in four agricultural zones in Tanzania. At least partial genome sequences of viruses potentially belonging to 25 genera were detected. The greatest virus diversity was detected in the eastern and northern zones, whereas wild plants in the Lake zone and especially in the southern highlands zone showed only a few viruses. The RT-PCR analysis of all collected plant samples confirmed the presence of yam bean mosaic virus and peanut mottle virus in wild legume plants. Of all viruses detected, only two viruses, cucumber mosaic virus and a novel bromovirus related to cowpea chlorotic mottle virus and brome mosaic virus, were mechanically transmitted from wild plants to common bean plants. The data generated during this study are crucial for the development of viral disease management strategies and predicting crop viral disease outbreaks in different agricultural regions in Tanzania and beyond.[Formula: see text] Copyright © 2021 The Author(s). This is an open access article distributed under the CC BY 4.0 International license.

Natural Pest Regulation and Its Compatibility with Other Crop Protection Practices in Smallholder Bean Farming Systems.

Common bean (Phaseolus vulgaris) production and storage are limited by numerous constraints. Insect pests are often the most destructive. However, resource-constrained smallholders in sub-Saharan Africa (SSA) often do little to manage pests. Where farmers do use a control strategy, it typically relies on chemical pesticides, which have adverse effects on the wildlife, crop pollinators, natural enemies, mammals, and the development of resistance by pests. Nature-based solutions -in particular, using biological control agents with sustainable approaches that include biopesticides, resistant varieties, and cultural tools-are alternatives to chemical control. However, significant barriers to their adoption in SSA include a lack of field data and knowledge on the natural enemies of pests, safety, efficacy, the spectrum of activities, the availability and costs of biopesticides, the lack of sources of resistance for different cultivars, and spatial and temporal inconsistencies for cultural methods. Here, we critically review the control options for bean pests, particularly the black bean aphid (Aphis fabae) and pod borers (Maruca vitrata). We identified natural pest regulation as the option with the greatest potential for this farming system. We recommend that farmers adapt to using biological control due to its compatibility with other sustainable approaches, such as cultural tools, resistant varieties, and biopesticides for effective management, especially in SSA.

Evaluation of different crop rotation schemes for organic common bean production under mild-winter climatic conditions

Evaluation of different crop rotation schemes for organic common bean production under mild-winter climatic conditions

Genome-Environment Association Analysis for Bio-Climatic Variables in Common Bean (Phaseolus vulgaris L.) from Brazil.

Abiotic stress is a limiting factor for common bean (Phaseolus vulgaris L.) production globally. The study of the genotypic, phenotypic, and bio-climatic variables in a broad set of accessions may assist the identification of genomic regions involved in the climatic adaptation of the common bean. We conducted a genotyping-by-sequencing analysis using 28,823 SNPs on 110 georeferenced common bean accessions from Brazil to discover associations between SNPs and bio-climatic indexes. The population structure analysis clustered the accessions into two groups corresponding to the Andean and Mesoamerican gene pools. Of the 19 bioclimatic variables, 17 exhibited a significant association with SNPs on chromosomes Pv01, Pv02, Pv03, Pv04, Pv06, Pv09, Pv10, and Pv11 of common bean. Ten candidate genes were associated with specific bio-climatic variables related to temperature and precipitation. The candidate genes associated with this significant Pv09 region encode a Platz transcription factor family protein previously reported to be an essential regulator of drought stress. The SNP markers and candidate genes associated with the bio-climatic variables should be validated in segregating populations for water stress, which could further be used for marker-assisted selection. As a result, bean breeding programs may be able to provide advances in obtaining drought-tolerant cultivars.

Preliminary evaluation of wild bean (Phaseolus spp.) germplasm for resistance to Fusarium cuneirostrum and Fusarium oxysporum

AbstractFusarium root rot (Fusarium cuneirostrum; FRR) and Fusarium wilt (Fusarium oxysporum; FW) are major constraints on common bean (Phaseolus vulgaris L.) production worldwide because limited genetic resistance is available in current cultivars. Wild accessions have greater genetic diversity than cultivated germplasm and could provide novel sources of resistance for these diseases. We screened 248 wild bean accessions in a greenhouse setting for responses to both FRR and FW and recorded disease severity; resistance was observed in 21 and 16 accessions, respectively. Accession PI417775 was the most resistant to FRR, exhibiting very few symptoms, whereas accessions PI661845 and PI535441 were the most resistant to FW. Only accessions MX‐GT‐1 and PI535445 were resistant to both FRR and FW. Overall, accessions collected from Andean regions had greater disease symptoms (5.4 ± 1.28 for FRR; 5.8 ± 1.12 for FW) than accessions collected from Middle America (4.7 ± 1.33 for FRR; 4.42 ± 1.04 for FW), though the highest and lowest disease scores for FRR were both found in the Middle American accessions. Introgression of Fusarium resistance from wild bean accessions into cultivated lines provides an avenue to improve disease resistance in elite cultivars.

Variable tillage depth and chemical fertilization impact on irrigated common beans and soil physical properties

Common bean (Phaseolus vulgaris L.) is an important grain crop in the world. Despite suitable soil-climatic conditions and high export potential, irrigated common bean production in Ukraine under performs due to a lack of sustainable management practices. The objective of our study was to evaluate the temporal effects of nitrogeN–Phosphorus (N–P) fertilization rates and tillage depth on the growth, yield, and water-use efficiency of common beans and selected soil physical properties. A 2 × 3 factorial experiment in a completely randomized design with four replications was conducted (2014–2016) at the Agricultural Land Cooperative Farm in the Kherson region of southern Ukraine. The factors were tillage depth (shallow tillage 0–20 cm vs. deep tillage of 0–30 cm) and N–P fertilization (control, N45P45, and N90P90 kg/ha). While tillage depth showed a marginal impact on the growth and yield of common beans, the N–P fertilization, in contrast, exerted significant effects on beans. Grain yields consistently increased by 25–30 % under N45P45 and N90P90 compared to the control; however, the effects of both N45P45 and N90P90 on grain yields were statistically similar. Likewise, the crude protein content was significantly higher by 17 % under N90P90 when compared to the control. As expected, the water-use efficiency (WUE) was significantly higher by 22–27 % under N45P45 and N90P90 when compared with the control; however, the N45P45 and N90P90 effects on WUE were non-significant. A similar effect (25–33 %) of N–P fertilizer was observed on irrigation-use efficiency (IUE) of beans. Soil bulk density (ρb) decreased significantly by 3 % in response to the temporal effects of the 0–30 cm tillage depth than that of the 0–20 cm tillage depth. Likewise, the 0–30 cm tillage depth significantly increased water infiltration by 7 % compared to the 0–20 cm tillage depth. The boundary line technique to evaluate the relationship between N–P fertilization and grain yield indicating that N45P45 produces near maximum economic grain production (95 %) comparable with N90P90, suggesting a savings of 45 kg/ha of both nitrogen (N) and phosphorus (P) fertilizers. While the impact of N–P fertilization was equally effective under both tillage depths, our results recommended that shallow tillage (0–20 cm) can be equally effective for irrigated common bean production to avoid deep tillage (0–30 cm).

Productivity and gas exchanges of the common bean subjected to inoculation and nitrogen fertilization

Beans are one of the main foods consumed in Brazil. It is considered an essential ingredient in the basic diet of Brazilians. As a management practice, aiming to supply N and increase crop productivity, producers have used the association of seed inoculation with nitrogen fertilization. Thus, the objective of this study is to evaluate the effects of split nitrogen fertilization and seed inoculation on common bean productivity. The experiment was carried out in completely randomized blocks and a 2x2x3 factorial design with four replications. The first factor was seed inoculation (presence or absence) with peat inoculant containing the strains SEMIA 4077 and SEMIA 4080 from R. tropici and the strain SEMIA 4088 from R. freirei. The second factor was the parceling of nitrogen cover fertilization (80+40 and 60+60 kg ha-1 of N at 20 and 40 days after emergence (DAE)). The third factor was time of assessment (50, 65 and 80 DAE). The inoculated bean showed a 5% higher leaf N content than non-inoculated ones. Transpiration and liquid photosynthesis rates were higher in inoculated plants and in those with 60+60 kg ha-1 of N. However, productivity was 13% higher in uninoculated beans regardless of nitrogen fertilization.

Effects of Rhizobium tropici azide-resistant mutants on growth, nitrogen nutrition and nodulation of common bean (Phaseolus vulgaris L.)

Inoculation with Rhizobium tropici and Rhizobium freirei can partially supply the nitrogen demand required for normal development and high productivity of common bean (Phaseolus vulgaris L.). Here, a simple and low-cost approach was used to select R. tropici sodium azide-resistant mutants with improved efficiency as microsymbiont of common bean. We mutagenized R. tropici CIAT889 by treatment with methyl methanesulfonate (MMS) and selected azide-resistant mutants. Six mutants (AzR14, AzR15, AzR16, AzR17, AzR18, and AzR19) with varying levels of resistance were obtained and characterized for symbiotic traits and performance upon inoculation of common bean. Mutants grew and produced exopolysaccharides similar to the CIAT899 wildtype; however, swarming motility, biofilm, and auxin production were altered. About nodulation, shoot biomass, and nitrogen content, the performance of mutant strains was improved or similar to that of CIAT899. All mutants enhanced nodulation of common bean; furthermore, AzR14, AzR18, and AzR19 increased nodule biomass by 25%–36%. AzR18 and AzR19 increased shoot biomass by up to 13% compared to CIAT899, whereas AzR14, AzR15, AzR16, and AzR17 reduced biomass accumulation by 9%–19%. In addition, AzR18 and AzR19 showed higher motility or biofilm production than the other mutant strains, suggesting that these traits are involved in bacterial symbiotic effectiveness. Shoot N content do not differ between plants inoculated with the CIAT899 or mutant strains, although plants inoculated with AzR18, AzR19 and CIAT899 had increased the shoot N as compared to uninoculated plants grown at N-limiting conditions. Our results demonstrated the possibility to improve the performance of the R. tropici microsymbiont through induced mutagenesis followed by the selection of azide resistant mutants. This approach allowed to identify the AzR18 and AzR19 strains, which showed superior nodulation and symbiotic effectiveness than CIAT899 while providing equivalent amounts of N to the inoculated plants. We propose the AzR18 and AzR19 as promising candidates for developing new and more efficient inoculants for common bean, nevertheless further trials under field conditions are required to confirm their superior performance to the wild strain.

Assessment of the Origin and Diversity of Croatian Common Bean Germplasm Using Phaseolin Type, SSR and SNP Markers and Morphological Traits.

Landraces represent valuable genetic resources for breeding programmes to produce high-yielding varieties adapted to stressful environmental conditions. Although the common bean (Phaseolus vulgaris L.) is an economically important food legume for direct human consumption worldwide, common bean production in Croatia is based almost exclusively on landraces and there is no common bean breeding program. Information on phaseolin type and results of population structure and genetic diversity obtained by analysis of SSR and SNP markers, in combination with the morphological characterization of 174 accessions of 10 common bean landraces (morphotypes), enabled thorough classification of accessions. The accessions were classified into phaseolin type H1 (“S”) of Mesoamerican origin and phaseolin types H2 (“H” or “C”) and H3 (“T”) of Andean origin. By applying distance- and model-based clustering methods to SSR markers, the accessions were classified into two clusters at K = 2 separating the accessions according to the centres of origin, while at K = 3, the accessions of Andean origin were further classified into two clusters of accessions that differed in phaseolin type (H2 and H3). Using SNP markers, model-based analysis of population structure was performed, the results of which were consistent with those of SSR markers. In addition, 122 accessions were assigned to 14 newly formed true-type morphogenetic groups derived from three different domestication events: (1) Mesoamerican (H1A) (“Biser”, “Kukuruzar”, “Tetovac”, “Trešnjevac”), (2) Andean—indeterminate type (H2B1) (“Dan noć”, “Sivi”, “Puter”, ”Sivi prošarani”, “Trešnjevac”) and (3) Andean—determinate type (H3B2) (“Bijeli”, “Dan noć”, “Puter”, “Trešnjevac”, “Zelenčec”). The rest of the accessions could represent putative hybrids between morphogenetic groups. The differences between the true-type groups of accessions were further analysed based on nine quantitative traits, and the subsets of traits that best distinguish among centres of origin (A: Mesoamerican, B: Andean) and genetic groups (H1A, H2B1, H3B2) were proposed.

Potato peel alleviation of the negative effects of salinity in bean (Phaseolus vulgaris L. ‘Valentine’)

Soil salinity is a serious problem that negatively affects the productivity of plants. Reducing the impact of salinity to sustain production is a goal of scientists. The objective of this study was to determine the effect of potato peel amendments at different rates in reducing the negative impact of saline water. Common bean (Phaseolus vulgaris L. ‘Valentine’) was grown in soil mixed with potato peel at different rates (0%, 2.5%, 5%, and 7.5%). To achieve this objective, plants were irrigated with three levels of saline water (0, 50, and 100 mmol L−1) to induce stress at the vegetative stage. The results demonstrated the significant reduction in physiological parameters, plant growth, and yield of common bean after irrigation with saline water. Soil amendment with different rates of potato peel significantly increased the number of pods per plant, weight of pods per plant, pod length, chlorophyll content, and relative water content of common bean irrigated with saline water (50 mmol L−1) as compared with non-amended soil. Potato peel application also reduced electrolyte leakage and improved soil properties by reducing the salinity of the soil. Furthermore, among all potato peel rates used in this investigation, the 7.5% rate had a better result for common bean production. Conversely, potato peel did not improve the yield of beans grown under a high concentration of saline water (100 mmol L−1). In conclusion, soil amendments with potato peel at a 7.5% rate could be successfully used as a cost effective management practice to enhance bean production in soils stressed with high salt content.

English

Anthracnose disease (Colletotrichum lindemuthianum (Sacc. et. Magn) Lams. Scrib.) is one of the most devastating diseases that constrain common bean production in Uganda. A cascading pedigree pyramiding scheme was used to develop common bean populations to evaluate the effectiveness of pyramided and single resistance genes (Co-42, Co-43, Co-5, and Co-9) on disease development. Detached leaf trifoliates of F4:6 genotypes were screened with four C. lindemuthianum races (352, 713, 767 and 2047). Disease severity data were subjected to ANOVA. Races, genotypes and Race x Genotype interaction were significant. Genes Co-42 and Co-5 conferred resistance to the four races and the gene pyramids Co-42+Co-5+Co-9 and Co-42+Co-5 had the lowest severity scores. Gene Co-43 conferred resistance to race 352 and weak resistance to race 713; whereas, gene Co-9 conferred resistance to race 352.  Co-43+Co-9 gene pyramid showed resistance only to race 352. The Co-42 and Co-5 genes conferred resistance to all the four races 352, 713, 767 and 2047. The single gene Co-42 was not significantly different from the pyramids Co-42+Co-5+Co-9 and Co-42+Co-5 (P<0.01). Similarly, the Co-5 gene was not significantly different from Co-42+Co-5, Co-42+Co-9 and Co-5+Co-9 pyramids. The Co-9 gene showed antagonism in all pyramids. These results indicate that pyramiding of resistance genes would be effective for disease management in Uganda, but pyramids with Co-9 gene would be less effective. Key words: SCAR markers, Colletotrichum lindemuthianum, broad-spectrum resistance.

English

Soil acidity and micronutrient deficiency is a major constraint affecting common bean production in Western Kenya. Farmers in the region have access to the two fertilizers Mavuno and Sympal fortified with different micronutrients and recommended for legumes; however, the performance of beans in the region remains low. A field experiment was, therefore, conducted in two sites in Nandi county, western Kenya, to determine the effect of using customized micronutrient fertilizer with lime on common bean yield. A factorial experiment was set up in a randomized complete block design consisting of three fertilizer types and lime treatments applied at two levels (0 and recommended rate). The fertilizer treatments were Mavuno (0 and 185 kg ha-1), Sympal (0 and 125 kg ha-1), Diammonium phosphate (0 and 62.5 kg ha-1) and lime (0 and 1.6 or 2.0 tons ha-1 depending on the lime requirement for the site). The experiment was run for two seasons, 2019 long and short rain seasons. Data were collected on nutrient uptake, crop growth and yield. The application of Mavuno fertilizer with lime significantly increased grain yield by 42, 30 and 27 % compared with control, Sympal and DAP, respectively. The application of Sympal and DAP did not have a significant effect on bean grain yield. Mavuno fertilizer with lime performed better in improving bean yield compared to the standard practice (DAP) and Sympal fertilizer. These results demonstrate the importance of using Mavuno fertilizer containing micronutrients Mo and B in combination with lime in improving legume production in Western Kenya. Key words: Common bean, customized fertilizer, lime, macronutrient, micronutrients, soil acidity.

Genetic dissection of drought resistance based on root traits at the bud stage in common bean.

A whole-genome resequencing-derived SNP dataset used for genome-wide association analysis revealed 196 loci significantly associated with drought stress based on root traits. Candidate genes identified in the regions of these loci include homologs of known drought resistance genes in A. thaliana. Drought is the main abiotic constraint of the production of common bean. Improved adaptation to drought environments has become a main goal of crop breeding due to the increasing scarcity of water that will occur in the future. The overall objective of our study was to identify genomic regions associated with drought resistance based on root traits using genome-wide association analysis. A natural population of 438 common bean accessions was evaluated for root traits: root surface area, root average diameter, root volume, total root length, taproot length, lateral root number, root dry weight, lateral root length, special root weight/length, using seed germination pouches under drought conditions and in well-watered environments. The coefficient of variation ranged from 11.24% (root average diameter) to 38.19% (root dry weight) in the well-watered environment and from 9.61% (root average diameter) to 39.05% (lateral root length) under drought stress. A whole-genome resequencing-derived SNP dataset revealed 196 loci containing 230 candidate SNPs associated with drought resistance. Seventeen candidate SNPs were simultaneously associated with more than two traits. Forty-one loci were simultaneously associated with more than two traits, and eleven loci were colocated with loci previously reported to be related to drought resistance. Candidate genes of the associated loci included the ABA-responsive element-binding protein family, MYB, NAC, the protein kinase superfamily, etc. These results revealed promising alleles linked to drought resistance or root traits, providing insights into the genetic basis of drought resistance and roots, which will be useful for common bean improvement.

Evaluation of Improved Common Bean (Phaseolus vulgaris L.) Varieties for Yield and Yield Components at West Hararghe, Eastern Ethiopia

Common bean is playing a crucial role across the world mainly in the warm and lowland areas of the country including Ethiopia. Understanding the level of drought tolerance of the varieties available in each country is of paramount importance for breeding common bean for drought adaptation. However, the production of common bean is mainly limited due to lack of high yielding potential varieties and frequent and recurrent drought. Hence, the study was aimed to evaluate and identify the superior performance and genetic potential of improved common bean varieties for yield and yield related traits against drought. A total of 10 recently released improved common bean varieties were evaluated using a randomized complete block design (RCBD) with three replications at Mieso during the main cropping season of 2018 and 2019. The information generated on the drought tolerance of the available varieties should help in the design of a breeding strategy that incorporates adaptation traits with commercial characteristics preferred by common bean farmers for varieties to be grown in diverse environments. The combined analyses of variance revealed the presence of tremendous genetic variation among improved common bean varieties for all the studied traits except plant height and stand count at harvest, which implies the availability of substantial genetic variation among varieties. Overall, SER-125, SER-19 and Nasir common bean varieties had better performance compared to the other varieties for yield and the yield related traits. The maximum grain yield was obtained from SER-125 (2620 kgha-1) followed SER-19 (2612 kgha-1) and Nasir (2583.33 kgha-1) common bean varieties and identified as the superior improved common bean varieties. Eventually, the effect of varieties on grain yield was significant and the best performing varieties of common bean would be recommended for the specific community and its vicinity even though further study should be carried out including a number of recently released varieties for improved common bean production in the target area and also to put the recommendation on strong basis. Therefore, based on the results of this adaptation experiment, SER-125, SER-19 and Nasir were recommended for production and adoption at Mieso and other similar environments.

Common bean SNP alleles and candidate genes affecting photosynthesis under contrasting water regimes

Water deficit is a major worldwide constraint to common bean (Phaseolus vulgaris L.) production, being photosynthesis one of the most affected physiological processes. To gain insights into the genetic basis of the photosynthetic response of common bean under water-limited conditions, a collection of 158 Portuguese accessions was grown under both well-watered and water-deficit regimes. Leaf gas-exchange parameters were measured and photosynthetic pigments quantified. The same collection was genotyped using SNP arrays, and SNP-trait associations tested considering a linear mixed model accounting for the genetic relatedness among accessions. A total of 133 SNP-trait associations were identified for net CO2 assimilation rate, transpiration rate, stomatal conductance, and chlorophylls a and b, carotenes, and xanthophyll contents. Ninety of these associations were detected under water-deficit and 43 under well-watered conditions, with only two associations common to both treatments. Identified candidate genes revealed that stomatal regulation, protein translocation across membranes, redox mechanisms, hormone, and osmotic stress signaling were the most relevant processes involved in common bean response to water-limited conditions. These candidates are now preferential targets for common bean water-deficit-tolerance breeding. Additionally, new sources of water-deficit tolerance of Andean, Mesoamerican, and admixed origin were detected as accessions valuable for breeding, and not yet explored.

Synerging of Root Traits and Agronomic Practices in Common Bean Production Improvement under Acidic Soil

The most challenging in twenty first century is the cause and consequences of Climate change and variability. It is hastening frequently by over population more in developing countries. Thus, it is affected several sectors, while Agriculture is the most vulnerable for climate change. As a result both biotic and abiotic factors are bottle neck for food security and sustainability. From abiotic factor, soil acidity is the frequently observed at area where received intensive rainfall due to top soil and metallic elements washed out. Soil acidity is arsenic, and causes abortion of expected production, especially susceptible crops such as Common bean. To overcome this problem, agronomic practices such as lime application, soil conservation techniques and appropriate root traits were reported. Root system architectures traits such as higher basal root number between 12 to 16, basal root whorl number of around 4, and shallow root angle of less than 15° were reported suitable to withstand soil acidity. Agronomic practices alone reported as it is tedious and also difficult to get complete genotypes with full of desired acidity resistance root traits. Hence several reported explained that using the desired root traits for acidity resistance genotypes and important agronomic practices obtained more valuable results as form of integration. Therefore, using the appropriate root traits and agronomic practices support with each other to reduces the syndrome of soil acidity impacts.

Intensification of common bean and maize production through rotations to improve food security for smallholder farmers.

A field experiment was conducted to understand whether non-formalized monocultures of maize could be substituted by the rotations with common bean on smallholder farms. This study was installed in the northern highlands of Tanzania along the slopes of the highest African peak of Mt. Kilimanjaro with the predominance of smallholder farmers. Cropping seasons (S), cropping systems (C), bean varieties (V), and their interactions were evaluated. Data collected were plant height, ground coverage, total biomass, number of pods per bean and seeds per pod, 100-seed weight, and grain yield. Results indicated that bean in long rainy seasons produced significantly larger grain yields as an effect of S (3.3 t ha−1) in 2015, C (3.4 t ha−1) in intercrop, V (2.7 t ha−1) in local bean, S × C (4.4 t ha−1) in 2015 in intercrop, S × V (3.4 t ha−1) in improved bean in 2015, C × V (4.6 t ha−1) in intercropped local bean, and S × C × V (5.0 t ha−1) in intercropped local bean in 2017. In a short rainy season, significantly larger bean grain yield (1.8 t ha−1) was recorded as an effect of C when sown subsquent to maize. The effects of V and/or C × V were not significant on bean grain yield during short rainy season. Maize in long rainy seasons produced significantly larger grain yields as an effect of C (2.9 t ha−1) but not for S and S × C in rotation with the local bean. In short rainy seasons, significantly larger maize grain yield was produced in 2015 (2.6 t ha−1) but the effects of C and S × C were not significant in 2015 and 2016. This study concluded that inclusion of intercrops (of maize and common bean) as part of a rotation with one of these crops significantly improved grain yields and hence provided promising grounds of the options for sustainable food production on smallholder farms.

Response of the common bean to liquid fertilizer and Rhizobium tropici inoculation

The common bean production system is majorly based on the use of granular fertilizers to provide nutrients for the crop. Studies on the use of liquid fertilization at an appropriated depth and, seed inoculation with Rhizobium tropici can provide significant increases in the grain yield of the common bean. The objective of this study was to determine the growth and productivity of common bean as affected by N-P formulations, application depths and the inoculation with R. tropici. Field experiments were carried out in 2015 and 2016 cropping years using a complete block design, in a 2x2x2 factorial arrangement, with four replicates. The treatments involved the combination of N-P formulation (granular and liquid), two application depths of the N-P formulation (6 and 12 cm) and with or without rhizobia inoculant. The plant density (PD), number of pods (NP), number of grains (NG), mass of 100 grains (M100) and grain yield (GY) were determined. The granular and liquid N-P formulations provided similar results for PD, NP, NG, and GY of common bean. Similarly, the application depth of the N-P formulations did not affect GY. Inoculation of the seed with R. tropici stimulated NP and NG, increasing GY. Growth and productivity parameters were equally affected by the type of formulation and application depth; however, GY was greater with rhizobial inoculant. Thus, the liquid N-P formulation, applied at 6 cm depth, associated with rhizobial inoculant can improve the crop management providing better control of application uniformity, minimal soil mobilization, less fuel consumption, and increased grain yield.

Sustainable production of common beans: inoculation, co-inoculation and mineral fertilization in early-cycle cultivars

Using sustainable management to maximize crop yield without increasing production costs is one of the great challenges of modern agriculture. This study aimed to evaluate the effect of nitrogen (N) supply management, associating inoculation with Rhizobium tropici, co-inoculation schemes with Azospirillum brasilense and mineral top-dressing fertilization, on the agronomic and qualitative performance of early-cycle common bean cultivars. The experiment was installed in a randomized block design, in a 2 x 12 factorial scheme (2 cultivars and 12 N supply management), with four repetitions. The N supply management consisted of the association of mineral fertilization with N (45 and 90 kg ha−1 of N in top-dressing), inoculation of seeds with Rhizobium tropici and co-inoculation of seeds and leaves with Azospirillum brasilense. The agronomic and qualitative performance of common bean was affected by the nitrogen supply management and by the cultivars, and the response was independent of the interaction between cultivars and N supply management. Except for plant dry mass, all variables analyzed showed maximum response in the treatment of seed inoculation with Rhizobium tropici, leaf-spray of Azospirillum brasilense and mineral top-dressing fertilization with 90 kg ha−1 of N, which led to a 27% increase in yield compared to the control. The cultivar IAC Imperador has a superior agronomic performance (grain yield = 2,840 kg ha−1) compared to IPR Curió (2,484 kg ha−1). The results demonstrated the feasibility of using co-inoculation with Azospirillum brasilense as a tool to increase yield, grain quality and sustainability in common bean production systems.

Demonstration of Common Bean Varieties (Dursitu and Chercher) in the Gurawa and Kurfa Chele Districts, East Hararghe Zone, Oromia Region, Ethiopia.

Common bean is becoming increasingly important in eastern Ethiopia because of the recurrent late-onset and early termination of rainfall. It is an important crop under various intercropping systems. The major problems of common bean production in Eastern Ethiopia are inaccessibility to improved common bean varieties, low extension intervention, and inferior performance of local varieties. Hence, its specific objectives were to demonstrate the two improved common bean varieties (Dursitu and Chercher) with the local one; to evaluate their performances and identify a variety that meets farmers’ criteria. Gurawa and Kurfa Chele districts were identified from Eastern Hararghe Zone using purposive sampling technique based on common bean production potential. Two kebeles were identified from each district. Three model farmers were selected from each kebele depending on common bean production potential. Training is one of the important extension methods to enhance and integrate the farmers’ indigenous knowledge and skill with improved practices. Field days were organized in June for Belg and September for the Maher seasons. The common beans were compared and prioritized based on participants’ criteria. Chercher variety was selected first, Dursitu second and the local common bean third based on their maturity dates, colour and market demand. In general, participants’ capability and skill on the improved common bean production technologies increased. The ground for further popularization and dissemination of the two improved common bean technologies was established.