Common Bean Improvement Research Articles

Exploring agro-morphological profiles of Phaseolus vulgaris germplasm shows manifest diversity and opportunities for genetic improvement

Common bean (Phaseolus vulgaris) is a seed crop with huge potential to contributing to food security in developing countries. In crop improvement, assessing genetic variability is a decisive step, requiring characterization of available crop germplasm. The present study aims at characterizing 39 common bean genotypes from various locations in Cameroon and five from Kenya using 19 qualitative and 36 quantitative traits of high descriptive values. Diversity among germplasm was assessed by determining diversity indices and carrying out multivariate analysis. Seventeen out of the nineteen qualitative traits (89.47%) were polymorphic, displaying each at least two phenotypic classes. High diversity was found. Average observed and expected number of phenotypic classes per trait were 3.74 and 2.53 respectively. Nei's genetic diversity value of 0.49 and Shannon-Weaver diversity index estimates of 0.74 were found. Significant differences were observed among genotypes for all measured quantitative traits. Yield traits showed significant correlation with other related quantitative traits. Cluster analysis separated the studied germplasm into three distinct groups, with the clustering pattern not showing any connection with location. The test of equality revealed significant difference between these clusters for most quantitative traits. Mahalanobis D2 statistics revealed germplasm of cluster I and III as potential parents for future breeding programs. This study identified genotypes with desirable agronomic traits such as higher number of seeds per pod, lower number of days to maturity, higher number of pods per plant, and higher yield. These and other important discriminatory traits are discussed and proposed for genetic improvement of common bean.

Genetic variation in a tepary bean (Phaseolus acutifolius A. Gray) diversity panel reveals loci associated with biotic stress resistance.

Tepary bean (Phaseolus acutifolius A. Gray), indigenous to the arid climates of northern Mexico and the Southwest United States, diverged from common bean (Phaseolus vulgaris L.), approximately 2 million years ago and exhibits a wide range of resistance to biotic stressors. The tepary genome is highly syntenic to the common bean genome providing a foundation for discovery and breeding of agronomic traits between these two crop species. Although a limited number of adaptive traits from tepary bean have been introgressed into common bean, hybridization barriers between these two species required the development of bridging lines to alleviate this barrier. Thus, to fully utilize the extant tepary bean germplasm as both a crop and as a donor of adaptive traits, we developed a diversity panel of 422 cultivated, weedy, and wild tepary bean accessions which were then genotyped and phenotyped to enable population genetic analyses and genome-wide association studies for their response to a range of biotic stressors. Population structure analyses of the panel revealed eight subpopulations and the differentiation of botanical varieties within P. acutifolius. Genome-wide association studies revealed loci and candidate genes underlying biotic stress resistance including quantitative trait loci for resistance to weevils, common bacterial blight, Fusarium wilt, and bean common mosaic necrosis virus that can be harnessed not only for tepary bean but also common bean improvement.

Prevalence and Host Resistance to Common Bean Rust Disease in Western and Central Kenya

Rust, caused by Uromyces appendiculatus (Pers.) Unger, is among the most devastating diseases of the common bean (Phaseolus vulgaris L.) worldwide. The pathogen is highly genetically variable, causing severe epidemics under favourable weather conditions. The objectives of this study were to determine the distribution of bean rust in major production areas in Kenya and identify potential sources of resistance for breeding. A field survey was conducted in five counties targeting smallholder common bean farmers in western and central Kenya, where data on the incidence and severity of bean rust and crop management practices by farmers were recorded. Additionally, seeds of the evaluated genotypes were collected from farms visited for further testing. A total of 77 common bean genotypes were subjected to natural infection under field conditions and inoculated with races 29–1, 29–3, 61–1, and 63–1 of rust under greenhouse conditions at the University of Embu. The gene pool affiliation of the genotypes was determined through the phaseolin protein marker analysis. Rust incidence and severity data were subjected to an analysis of variance using GenStat statistical software. The results showed that bean rust occurred in all counties although there were significant differences ( P < 0.001 ) in incidence and severity among the surveyed localities. Based on a 1–9 severity rating scale, Bungoma County recorded the highest mean severity of 3.99 and an incidence of 71%. Cultivar grown, use of fungicides, management of residues, and crop spacing had a significant effect on bean rust severity. Under field and greenhouse conditions, the genotypes revealed high variations in response to rust, with 71% of the genotypes being susceptible under greenhouse inoculations. Enclave, MU#13, UN2-Darkgreen, UN6-Nakholo, Kat X56, and KMR-11 genotypes were identified as resistant and can be used as prospective parents in common bean improvement programs in Kenya. This study revealed high occurrence and distribution of common bean rust and thus provides critical baseline information for common bean rust management in Kenya.

High yielding common bean (Phaseolus vulgaris L.) varieties 'NIFA Lobia Red-22 and NIFA Lobia Yellow-22

Common bean (Phaseolus vulgaris L.) improvement program was initiated at Nuclear Institute for Food and Agriculture (NIFA) in 2018. Germplasm from various research institutes and farmers’ fields in KP was collected. The collected germplasm was evaluated in non-replicated fashion in spring 2018 and 2019 at research farm of NIFA for plant type, yield and yield components. Six genotypes were finally selected based on seed color, growth habit and subsequently tested in replicated yield trials conducted at NIFA, Peshawar and on farmers’ fields at Charsadda in spring 2020 & 2021, at Agricultural Research Institute (ARI), Mingora, Swat and Agricultural Research Station (ARS), Chitral in Kharif 2020, and on farmers’ fields at different locations in Kuram in kharif 2020 and 2021. Two genotypes, NCB-Tajaki (NIFA Lobia Red-22) and NCB-Watani (NIFA Lobia Yellow-22) out yielded all other genotypes across all locations as well as seasons. In spring 2020 and 2021, NCB-Tajaki (NIFA Lobia Red-22) and NCB-Watani (NIFA Lobia Yellow-22) produced higher average seed yield of 2195 and 2206 kg ha-1, respectively, whereas in kharif 2020 and 2021, the two genotypes produced higher average seed yield of 2082 and 2075 kg ha-1, respectively compared with other genotypes. The two genotypes were approved by the KP Seed Council under the name NIFA Lobia Red-22 and NIFA Lobia Yellow-22 for general cultivation in common bean growing areas of the KP on 20-01-2022.

Elite Lines of Common Bean (Phaseolus vulgaris L.) are Showing Diversity for Yield Promoting Traits

Twelve elite lines of common bean were evaluated to identify diversity for morphological traits under rainfed conditions of Rawalakot, Azad Kashmir. The elite lines were found statistically different for the parameters under study. The elite line G-3990 produced highest grain yield per plant (23.45g) while lowest yield was recorded in NKB-1 (0.871g). G-3990 could be released as a variety in the mountainous regions for example in Azad Kashmir. Cluster analysis based on metric traits showed that the elite lines G-4258 and G-3661 having moderate grain yield per plant and 100-seed weight were grouped in same cluster. These lines could be utilized for the common bean improvement programme through breeding and hybridization. High heritability and genetic advance was estimated for 100-seed weight which indicated preponderance of additive genetic effects. For grain yield per plant, days to maturity and days to flowering the heritability estimates were moderate. It indicated a possible involvement of non-additive genes in their regulation.

Combining ability of common bean (Phaseolus vulgaris) genotypes for root traits across diverse environments

AbstractRoot system architecture is important for common bean (Phaseolus vulgaris) adaptability to diverse environments. Beans employ complex adaptive root mechanisms for coping with multiple stresses in production environments. Understanding genetic control of root traits is central to improvement of common bean for adaptation to marginal environments. The objectives of this study were to (i) determine combining ability of root and agronomic traits and (ii) estimate the heritability and genetic correlation of root and agronomic traits in common bean. Four bean lines with superior root traits were crossed with four locally adapted varieties in a North Carolina II mating scheme to generate 16 crosses. The 16 F1s were selfed and advanced to F2 generation. Eight parents and their F2 progenies were evaluated in an alpha‐Lattice design with two replications. General and specific combing ability mean squares were significant (p ≤ .05) for all traits measured. General predictability ratios ranged from .47 to .68 across locations suggesting that both additive and non‐additive gene action modulate root traits and seed yield. Positive and significant (p ≤ .05) phenotypic and genetic correlations revealed significant association between root traits and yield. Moderate to high heritability estimates of between .43 and .67 were realized. Such estimates point to possible deployment of a successful selection programme. Genotype AFR398 displayed significant positive GCA effects among its crosses for both root and agronomic traits hence a potential candidate genotype for inclusion in a bean genetic improvement programme for marginal environments.

Plant parasitic nematodes and disease severity of common bean lines evaluated for reaction to root knot nematodes infestation

Plant parasitic nematodes are important pests in crop production in sub-Saharan Africa. The objective of this study was to identify the occurrence of nematodes associated with common bean (Phaseolus vulgaris L.) and evaluate breeding lines for their reaction to Meloidogyne spp. in Ghana. Common bean rhizosphere soil was sampled and processed using Modified Baermann Tray method. Five nematode genera, namely Meloidogyne, Pratylenchus, Rotylenchulus, Helicotylenchus and Trichodorus were extracted. The first four genera listed above were prevalent across locations, with Trichodorus present in 30% of the fields sampled. The highest nematode population density of 319 juveniles per 200 cubic centimeter of soil was recorded for Meloidogyne spp. compared to 45 juveniles per 200 cubic centimeter, for Trichodorus. Twelve breeding lines were evaluated by inoculating roots of two-weeks-old plants with 2000 infective-stage juveniles of Meloidogyne sp. Reactions of test lines to Meldogyne sp. infection were assessed by determining the number of egg masses and galling index (GI) on roots. Reproduction index (RI) was used to classify test lines as resistant or susceptible. Significant differences (P < 0.05) were observed in the number of eggs, GI and RI among lines tested. No resistant line was identified; however, lines SEF 47, BFS 35 and BFS 60 were moderately resistant, with RI of 13.1, 17.4 and 23.7%, respectively. Line SEF 60, although classified as slightly resistant, recorded a 100 seed weight of 26.0 g, which was 60% higher than line SEF 53 with seed weight of 16.2 g. Moderately resistant common bean lines identified could be used in common bean improvement programmes to develop elite cultivars tolerant to root knot nematodes.

Evaluation of resistance to black bean aphid (Aphis fabae) in selected varieties and mutant genotypes of common bean (Phaseolus vulgaris)

AbstractCommon bean (Phaseolus vulgaris) is an important food crop across sub‐Saharan Africa. In Zambia, actual common bean yields are typically lower than potential yields because of the impact of invertebrate pests and plant diseases. Black bean aphids (Aphis fabae) (Hemiptera: Aphididae) negatively impact bean productivity directly by ingesting plant assimilates and indirectly by vectoring diseases such as bean common mosaic virus. Current breeding programmes aim to develop bean cultivars with improved yield and tolerance to pests. The objective of this study was to screen five common bean varieties (Rozi Koko, Mwezi Moja, Majesty, KK25 and AO‐1012‐29‐3A) and four mutation‐derived genotypes (CA 3, CA 15, CA 24 and CA 38) for resistance to black bean aphid. Commercial bean cultivars such as Kabulangeti and Carioca (variety from which all mutants were derived) were used as controls for the selected varieties and mutant genotypes, respectively. Several parameters of aphid resistance traits were assessed. Deterrence to aphid was assessed by settling preference while physical barriers to aphid feeding were evaluated by nymph survival. Reduction in palatability of phloem sap was evaluated by nymph development and mean relative growth rate. Electrical penetration graph recordings of feeding behaviour were performed in order to localise aphid‐resistant factors. Nymph development was significantly longer on AO‐1012‐29‐3A compared to Kabulangeti despite the fact that there were significantly fewer glandular trichomes on this line. The variety AO‐1012‐29‐3A can be used in genetic improvement of common bean for aphid resistance.

Improving Association Studies and Genomic Predictions for Climbing Beans With Data From Bush Bean Populations.

Common bean (Phaseolus vulgaris L.) has two major origins of domestication, Andean and Mesoamerican, which contribute to the high diversity of growth type, pod and seed characteristics. The climbing growth habit is associated with increased days to flowering (DF), seed iron concentration (SdFe), nitrogen fixation, and yield. However, breeding efforts in climbing beans have been limited and independent from bush type beans. To advance climbing bean breeding, we carried out genome-wide association studies and genomic predictions using 1,869 common bean lines belonging to five breeding panels representing both gene pools and all growth types. The phenotypic data were collected from 17 field trials and were complemented with 16 previously published trials. Overall, 38 significant marker-trait associations were identified for growth habit, 14 for DF, 13 for 100 seed weight, three for SdFe, and one for yield. Except for DF, the results suggest a common genetic basis for traits across all panels and growth types. Seven QTL associated with growth habits were confirmed from earlier studies and four plausible candidate genes for SdFe and 100 seed weight were newly identified. Furthermore, the genomic prediction accuracy for SdFe and yield in climbing beans improved up to 8.8% when bush-type bean lines were included in the training population. In conclusion, a large population from different gene pools and growth types across multiple breeding panels increased the power of genomic analyses and provides a solid and diverse germplasm base for genetic improvement of common bean.

Genetic diversity of common bean (Phaseolus vulgaris L.) ecotypes from Pakistan using Simple Sequence Repeats

Common bean (Phaseolus vulgaris L.) is a legume crop grown all over the world and is a very important food of mountain population of Pakistan for protein intake. The Western Himalayan Mountains are rich in biodiversity including unexplored landraces of the common bean crop. Unfortunately, very little attention has been given to this valuable crop in Pakistan, and it is being exported, majorly from Ethiopia, to meet the country’s requirements. The exploitation, utilization, preservation and multiplication of existing germplasm within the area are very important for sustainable production of the crop and enhancing the nutrition value for the local community in mountain regions. A research study was conducted for evaluation of biological diversity of common bean landraces from Azad Kashmir and Northern areas of Pakistan using morpho-physiological and molecular markers. Thirty-five common bean ecotypes along with one check variety were collected from different altitudes of Azad Kashmir and Northern Pakistan and screened for biological diversity. Morphological characterization revealed high genetic diversity in parameters including stem anthocyanin, growth type, days to flowering, pods/plant and 100 seeds weight. Genomic characterization using SSR markers, for allelic diversity evaluation among germplasm, also provided diverse profile with 83.3% polymorphism in banding pattern. The bulk of gene pool diversity evaluated within bean landraces may help to initiate breeding program for common bean improvement.

IMPROVING SEED YIELD AND PROTEIN CONTENT OF COMMON BEANS (PHASEOLUS VULGARIS L.) THROUGH MUTATION BREEDING

The common bean is a staple food and source of protein in many African countries. To date, genetic improvement of common bean in Egypt lags behind compared with other legume crops which mainly due to limited genetic resources. This study was carried out in three consecutive growing seasons (2016, 2017 and 2018) at Sakha Experimental Station, Horticulture Research Institute (HRI) at Kafr El-Sheikh governorate, Egypt. The study aimed to increase genetic variations in Nebraska bean cultivar through mutation breeding for selection of novel bean lines with higher seed yield and protein content. The experiment was arranged in a randomized complete blocks design (RCBD) with three replications. Seeds of Nebraska bean cultivar which widely grown in Egypt were treated with gamma rays three different doses (10, 20, and 30 kr), and selection was made at M2 and M3 generations for desired traits related to vegetative growth parameters, pod characteristics and seed yield components. These traits were significantly affected by irradiation treatments in M1 generation, and changes in plant height, number of branches per plant, number of pods and seeds per plant were generally favorable in M2 generation than control (un-irradiated plants). Analysis of variance in M3 generation showed a highly significant difference among M3 lines and control for vegetative and agronomical traits except for the traits of number of days to first flower and number of seeds per pod. Among 25 M3 lines, ten mutant lines were produced higher seed yield (4.3 to 108.6%) and protein content (0.08 to 2.79%) along with heavier seeds (3.5 to 35%) than original parent Nebraska cultivar. Hence, these lines should be evaluated for the desired traits and wide adaptability to biotic and abiotic stress to release new improved varieties in Egypt.

Genome‐wide association analysis of drought resistance based on seed germination vigor and germination rate at the bud stage in common bean

AbstractCommon bean (Phaseolus vulgaris L.) is an important food legume. However, drought influences its entire growth and development process and can cause yield losses. The influence of drought stress is the most severe in the bud stage. The major objective of our study was to identify a series of loci involved in drought stress response in the bud stage using association analysis. In this study, 361 common bean germplasms were used to investigate germination vigor (GV) and germination rate (GR) under distilled water and drought stress conditions. The common bean showed large variations in GV and GR, with GV ranging from 6.67 to 100% and 0 to 73.33% and GR ranging from 66.67 to 100% and 0 to 100% in distilled water and under drought stress, respectively. A genome‐wide association study (GWAS) of 361 accessions was conducted using 3,724,159 single nucleotide polymorphisms (SNPs) and revealed 2 and 11 candidate SNPs associated with relative germination rate (RGR) and relative germination vigor (RGV), respectively. Three loci were collocated with loci previously reported as being related to drought tolerance. A total of 180 candidate genes were identified, many of which were related to ion transport and oxidation‐reduction reactions. A major haplotype for RGV was identified on chromosome 6. These results provide new insight into the genetic basis of drought tolerance in common bean at the bud stage and provide candidate SNPs and genes that can be used to accelerate the drought tolerance improvement of common bean.

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.

Population structure and genetic diversity analyses of common bean germplasm collections of East and Southern Africa using morphological traits and high-density SNP markers.

Knowledge of genetic diversity in plant germplasm and the relationship between genetic factors and phenotypic expression is vital for crop improvement. This study's objectives were to understand the extent of genetic diversity and population structure in 60 common bean genotypes from East and Southern Africa. The common bean genotypes exhibited significant (p<0.05) levels of variability for traits such as days to flowering (DTF), days to maturity (DTM), number of pods per plant (NPP), number of seeds per pod (NSP), and grain yield per hectare in kilograms (GYD). About 47.82 per cent of the variation among the genotypes was explained by seven principal components (PC) associated with the following agronomic traits: NPP, NFF (nodes to first flower), DTF, GH (growth habit) and GYD. The SNP markers revealed mean gene diversity and polymorphic information content values of 0.38 and 0.25, respectively, which suggested the presence of considerable genetic variation among the assessed genotypes. Analysis of molecular variance showed that 51% of the genetic variation were between the gene pools, while 49% of the variation were within the gene pools. The genotypes were delineated into two distinct groups through the population structure, cluster and phylogenetic analyses. Genetically divergent genotypes such as DRK57, MW3915, NUA59, and VTTT924/4-4 with high yield and agronomic potential were identified, which may be useful for common bean improvement.

Selection for bean fly (Ophiomyia spp) resistance and agronomic performance in selected common bean (Phaseolus vulgaris L.) accessions

The bean fly (Ophiomyia spp) is one of several yield limiting insect pests of common bean (Phaseolus vulgaris L.) in eastern and southern Africa. High performing common bean cultivars with the bean fly resistance, good agronomic traits and market-preferred attributes are yet to be developed in the region. The objective of this study was to evaluate the bean fly resistance and agronomic performance of common bean accessions adapted to the eastern and southern African regions and to select parental lines for breeding. Ninety-nine common bean accessions were evaluated in bean fly hotspot areas in two locations in Malawi during the 2018 and 2019 growing seasons. Damage severity (BDS), plant mortality rate (PMR) and pupa count (PC) were measured to evaluate resistance to the bean fly. The following agro-morphological traits were assessed: the length between first internode and fifth internode at first flowering (FIL), number of nodes at the first flower (NFF), stem diameter (SD) at 50% flowering stage, days to 50% flowering (DTF), days to 90% physiological maturity (DTM), number of pods per plant (NPP), number of seed per pod (NSP) and grain yield in kg ha−1 (GYD). The analysis of variance revealed significant genotypic variation (p < 0.05) for both bean fly resistance and agro-morphological traits for common bean improvement. About 67.13% variation was explained by the first three principal components associated with BDS, PMR, DTF, SD, NPP, NSP and GYD. Phenotypic correlations between bean-fly resistance traits and grain yield were significant (p < 0.05) and negative, implying that direct selection for bean fly resistant genotypes could improve GYD. Twelve genotypes, namely, A55, A222, A429, Sinoni, ALB 196, MW3954, SIN526, CZ114-50, SCR63, MW3917, ALB133 and A344 showed high grain yield and exhibited resistance to the bean fly. These genotypes will be useful as parental lines for resistance breeding programs in the region.

Molecular characterization and insights into the origin of common bean (Phaseolus vulgaris L.) landraces of north western Himalayas

Common bean is the principal grain legume of North-India including Jammu & Kashmir and Ladhak. Owing to its high protein content, abundance of various micronutrients and essential amino acids and low cost, it is sometimes referred to as poor man’s meat. It is a very diverse crop and presents a rich reservoir of genetic resource to be explored. In the present study, we collected 102 common bean genotypes from different north western Himalayan regions of Jammu & Kashmir and Ladakh. This germplasm was then systematically purified and then characterised using SSRs. In order to examine the genetic diversity, various parameters were considered. The PIC values for the SSR loci ranged from 0.738 to 0.966 with an average of 0.899. The gene diversity between common bean genotypes ranged from 0.751 to 0.967. The major allele frequency ranged from 0.076 to 0.469 and the expected heterozygosity ranged from 0 to 0.135. Further, model based STRUCTURE analysis generated three subpopulations that correspond to distance based groups. Furthermore, the PCR assay for phaseolin locus led to the characterization of 81 genotypes into Meso-American and Andean types. Out of 81 genotypes, 40 possessed “S” type phaseolin and 41 possess “T” type phaseolin. The results of this study revealed the origin of common bean landraces grown in the north western regions of Jammu & Kashmir and Ladakh, India. The characterised material can be planned for conservation and can further be used as a genetic resource for improvement of common bean.

Performance Evaluation of Common Bean (Phaseolus vulgaris L.) Genotypes for Yield and Related Traits at Areka, Southern Ethiopia

Common bean is a source of dietary protein and the second most important legume crop in Africa next to faba bean. In Ethiopia common bean is the most important legume as the source of protein and export commodity. Hence, development of commercial varieties is one of the major tasks to meet increasing demand of the stake holders. To this effect, understanding the genetic variability, heritability and association between grain yield and other agronomic traits is necessary for effective plant breeding program. In this context, a field experiment was conducted during 2016/2017 cropping season at Areka Agricultural Research Center in southern Ethiopia with the objective of evaluating common bean genotypes for yield and related traits and also estimate the variability present among the genotypes. Treatments consisted of thirty three common bean genotypes were laid out in a randomized complete block design (RCBD) with three replications. Common bean genotypes exhibited considerable variations for agronomic traits and grain yield. Majority of the traits; plant height, number of nodes, internode length, leaf area, LAI, biological yield, pods per plant, HI and HSW had higher PCV. Genotypic coefficient of variance (GCV) varied from 1.88% to 37.72% with the highest GCV recorded for HSW. Heritability in broad sense (H2) ranged from 0.52% to 95.33% with the highest value observed for HSW. The present study revealed significant variation among genotypes for traits considered except few insignificant traits. In addition, almost all the genotypes were well adapted to the study area and hence, the high yielding genotypes could be directly used as seed sources for production of common bean and some of the genotypes with best diseases resistance reaction, and with high heritability can possibly be used in common bean improvement program.

In-Depth Characterisation of Common Bean Diversity Discloses Its Breeding Potential for Sustainable Agriculture

Legumes’ cultivation contributes services to agro-ecosystems and society, in line with the principles of sustainability. Among pulses, the common bean is one of the most important sources of plant proteins and other important nutrients for humans. Extensive phenotypic and genetic characterisations of unexplored bean germplasm are still needed to unlock its breeding potential. To the purpose, a panel of 192 diverse genotypes, mainly developed starting from European landrace accessions, was characterised for relevant morpho-phenological traits; a partially replicated experimental design was used. For each quantitative trait, Best Linear Unbiased Predictors and broad-sense heritability were estimated. The screened panel revealed a high level of diversity for most of the measured traits, especially for days to flowering and hundred-seed weight. The same material was also characterised by means of double-digest Restriction-site Associated DNA; a high number of SNP markers were successfully produced. The genotyping allowed understanding the fine genetic structure of the panel. Genetic information was also used to study morpho-phenological traits considering different genetic groups existing within the panel. At the same time, genotypes characterised by favourable traits were identified. The availability of such collection with its extensive characterisation, make this material an excellent resource for common bean improvement.

English

The present study was conducted to estimate the genetic variability, heritability, genetic advance and association among selected agronomic traits of common bean landraces from South western Kenya. The field experiment was conducted using 52 common bean landraces at the Kenya Agricultural and Livestock Research Organization (KALRO), Kisii Research Center during 2015 and 2016 main cropping seasons. The experimental design was randomized complete block (RCBD) with three replications. Analysis of variance revealed significant differences indicating the existence of genetic variability among the 52 landraces for 14 quantitative traits studied. The genotypic coefficient of variation ranged from 1.00% for biological yield to 84.69% for pod width, while the phenotypic coefficient of variation ranged from 2.34% for biological yield to 84.40% for number of branches. The estimated broad sense heritability ranged from 60.20% for seeds per plant to 87.57% for days to emergence. Estimates of genetic advance as percent of mean ranged from 10.15% for biological yield to 97.45% for number of branches. Positive and highly significant association of plant height, days from planting to 50% flowering, number of pods per plant and biological yield was observed with seed yield per plant, hence these traits may be directly attributed for the improvement of seed yield. High hereditability and genetic advance was obtained for plant height, 100 seed weight, pod width and number of branches, indicating additive gene effects in controlling the traits and these traits could be used as suitable criteria for selection and improvement of common bean in breeding programs. Key words: Phaseolus vulgaris, phenotypic variability, genotypic variability, quantitative traits, heritability, genetic advance, breeding. &nbsp

Common Bean Improvement Status (Phaseolus vulgaris L.) in Ethiopia

Common bean (Phaseolus vulgaris L; 2n=22) is the most important food legume rich in protein, minerals, and vitamins where its protein content is cheap and easily affordable for the famers of the country. The crop plays great role in maintaining the fertility of the soil through fixing atmospheric nitrogen and thus keeping diversity and stability of the agricultural system. Due to its importance, the total area allocated for common bean crop production and the yield obtained in Ethiopia is 357,299.89 ha and 540,238.94 tons respectively. The productivity of white and red common bean is 1.41 ton/ha and 1.59 ton/ha respectively in 2016 planting season. Since 1970s common bean improvement has been started in Ethiopia and since then more than 50 common bean varieties for different traits and for different agro ecologies were released through conventional breeding in Ethiopia. Currently, in common bean breeding; gene pyramiding against common bean diseases like ALS (Angular Leaf Spot), CBB (Common Bean Blight) and anthracnose and diversity assessment for diseases like CBB and ALS has been started using MAS (Marker Assisted Selection) in Southern Agricultural Research Institute at Hawassa. Therefore the aim of this article is to review common bean improvement status and to indicate some improvement gaps in Ethiopia.