Analyses of African common bean (Phaseolus vulgaris L.) germplasm using a SNP fingerprinting platform: diversity, quality control and molecular breeding (original) (raw)
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Molecular Biology Reports
Introduction Common bean is one of the widely consumed food security crop in Africa, Asia, and South America. Understanding genetic diversity and population structure is crucial for designing breeding strategies. Materials Two hundred and eighty-nine germplasm were recently collected from different regions of Ethiopia and introduced from CIAT to estimate genetic diversity and population structure using 11,480 DArTSeq SNP markers. Results The overall mean genetic diversity and polymorphic information content (PIC) were 0.38 and 0.30, respectively, suggested the presence of adequate genetic diversity among the genotypes. Among the geographical regions, landraces collected from Oromia showed the highest diversity (0.39) and PIC (0.30). The highest genetic distance was observed between genotypes collected from SNNPR and CIAT (0.49). In addition, genotypes from CIAT were genetically more related to improved varieties than the landraces which could be due to sharing of parents in the impr...
SNP marker diversity in common bean ( Phaseolus vulgaris L
Theoretical and Applied Genetics
Single nucleotide polymorphism (SNP) markers have become a genetic technology of choice because of their automation and high precision of allele calls. In this study, our goal was to develop 94 SNPs and test them across well-chosen common bean (Phaseolus vulgaris L.) germplasm. We validated and accessed SNP diversity at 84 gene-based and 10 non-genic loci using KASPar technology in a panel of 70 genotypes that have been used as parents of mapping populations and have been previously evaluated for SSRs. SNPs exhibited high levels of genetic diversity, an excess of middle frequency polymorphism, and a within-genepool mismatch distribution as expected for populations affected by sudden demographic expansions after domestication bottlenecks. This set of markers was useful for distinguishing Andean and Mesoamerican genotypes but less useful for distinguishing within each gene pool. In summary, slightly greater polymorphism and race structure was found within the Andean gene pool than within the Mesoamerican gene pool but polymorphism rate between genotypes was consistent with genepool and race identity. Our survey results represent a baseline for the choice of SNP markers for future applications because gene-associated SNPs could themselves be causative SNPs for traits. Finally, we discuss that the ideal genetic marker combination with which to carry out diversity, mapping and association studies in common bean should consider a mix of both SNP and SSR markers.
Theoretical and Applied Genetics, 2009
The East African highlands are a region of important common bean production and high varietal diversity for the crop. The objective of this study was to uncover the diversity and population structure of 192 landraces from Ethiopia and Kenya together with four genepool control genotypes using morphological phenotyping and microsatellite marker genotyping. The germplasm represented different common bean production ecologies and seed types common in these countries. The landraces showed considerable diversity that corresponded well to the two recognized genepools (Andean and Mesoamerican) with little introgression between these groups. Mesoamerican genotypes were predominant in Ethiopia while Andean genotypes were predominant in Kenya. Within each country, landraces from different collection sites were clustered together indicating potential gene flow between regions within Kenya or within Ethiopia. Across countries, landraces from the same country of origin tended to cluster together indicating distinct germplasm at the national level and limited gene flow between the two countries highlighting divided social networks within the regions and a weak trans-national bean seed exchange especially for landrace varieties. One exception to this may be the case of small red-seeded beans where informal cross-border grain trade occurs. We also observed that genetic divergence was slightly higher for the Ethiopian landraces compared to Kenyan landraces and that Mesoamerican genotypes were more diverse than the Andean genotypes. Common beans in eastern Africa are often cultivated in marginal, risk-prone farming systems and the observed landrace diversity should provide valuable alleles for adaptation to stressful environments in future breeding programs in the region.
African Journal of Biotechnology, 2014
The knowledge and understanding of the genetic variability of common bean (Phaseolus vulgaris L.) germplasm is important for the implementation of measures addressed to their utilizations and conservation. The objective of this study was to characterize common bean in Uganda using polymorphic molecular markers for use in hybridization and variety development. Genomic DNA was extracted from plants at the first trifoliate leaf stage growing in pots using the modified cetyltrimethylammonium bromide (CTAB) method. The gene pool membership (Andean vs. Mesoamerican) for each accession was established with the phaseolin marker. Simple sequence repeat (SSR) alleles were separated by capillary electrophoresis that provided further information on the organization of genetic diversity. The Andean and Mesoamerican genotypes were present in similar frequencies (51 vs. 49%, respectively). All SSR markers tested were polymorphic with mean polymorphism information content (PIC) of 0.8. The model-based cluster analysis of SSR diversity in the STRUCTURE software found three sub populations (K3.1, K3.2 and K3.3) genetically differentiated with moderate Wrights fixation indices (F ST) values 0.14, 0.12 and 0.09, respectively and many cases of admixture. The STRUCTURE result was confirmed by principal coordinate analysis (PCoA) which also clustered beans in three groups. Most Andean genotypes were included in K3.1 and Mesoamerican genotypes belonged to the K3.2 and K3.3 subgroups. This study sets the stage for further analyses for agronomic traits such as yield, resistance to biotic and abiotic stresses and the need for germplasm conservation.
African Journal of Biotechnology, 2016
The Ethiopian genetic center is considered to be one of the secondary centers of diversity for the common bean. This study was conducted to characterize the distribution of genetic diversity between and within ecological/geographical regions of Ethiopia. A germplasm sample of 116 landrace accessions was developed, which represented different common bean production ecologies and seed types common in the country. This sample was then analyzed with 24 simple sequence repeat (SSR) markers to assess the genetic diversity within and between common bean landraces, classifying them based on SSR clustering, and determining relationships between genetic and agroecological diversity. Representatives of both Andean and Mesoamerican gene pools were identified by STRUCTURE software analysis, as well as a high proportion of hybrid accessions as evidenced by a STRUCTURE K = 2 preset. At the optimum K = 5 preset value, mixed membership of Andean and Mesoamerican genotypes in some of the clusters was also seen, which supported previous findings. Cluster analyses, principal coordinate analysis, and analysis of molecular variance all indicated clustering of accessions from different collection sites, accompanied by high gene flow levels, highlighting the significant exchange of planting materials among farmers in different growing regions in the country. Values of allelic diversity were comparable to those reported in previous similar studies, showcasing the high genetic diversity in the landrace germplasm studied. Moreover, the distribution of genetic diversity across various bean-growing population groups in contrasting geographical/ecological population groups suggests elevated but underutilized potential of Ethiopian germplasm in common bean breeding. In summary, this study demonstrated the geographical, as well as gene pool diversity in common bean germplasm of Ethiopia. This substantial diversity, in turn, should be utilized in future common bean breeding and conservation endeavors in the nation.
Molecular Breeding
Common bean (Phaseolus vulgaris L.), one of the most important grain legume crops for direct human consumption, faces many challenges as a crop. Domesticated from wild relatives that inhabit a relatively narrow ecological niche, common bean faces a wide range of biotic and abiotic constraints within its diverse agroecological settings. Biotic stresses impacting common bean include numerous bacterial, fungal, and viral diseases and various insect and nematode pests, and abiotic stresses include drought, heat, cold, and soil nutrient deficiencies or toxicities. Breeding is often local, focusing on improvements in responses to biotic and abiotic stresses that are particular challenges in certain locations and needing to respond to conditions such as day-length regimes. This review describes the major breeding objectives for common bean, followed by a description of major genetic and genomic resources, and an overview of current and prospective marker-assisted methods in common bean breeding. Improvements over traditional breeding methods in CB can result from the use of different approaches. Several important germplasm collections have been densely genotyped, and relatively inexpensive SNP genotyping platforms enable implementation of genomic selection and related markerassisted breeding approaches. Also important are sociological insights related to demand-led breeding, which considers local value chains, from farmers to traders to retailers and consumers.
Genetic Resources and Crop Evolution, 2017
Molecular characterisation of common bean (Phaseolus vulgaris L.) accessions from Southwestern Uganda reveal high levels of genetic diversity The International Center for Tropical Agriculture (CIAT) believes that open access contributes to its mission of reducing hunger and poverty, and improving human nutrition in the tropics through research aimed at increasing the eco-efficiency of agriculture. CIAT is committed to creating and sharing knowledge and information openly and globally. We do this through collaborative research as well as through the open sharing of our data, tools, and publications.
Genomics, genetics and breeding of common bean in Africa: A review of tropical legume project
Plant Breeding
Common bean (Phaseolus vulgaris L.) is an important legume crop worldwide. The International Centre for Tropical Agriculture (CIAT) and its national partners in Africa aim to overcome production constraints of common bean and address the food, nutrition needs and market demands through development of multitrait bean varieties. Breeding is guided by principles of market-driven approaches to develop client-demanded varieties. Germplasm accessions from especially two sister species, P. coccineus and P. acutifolius, have been utilized as sources of resistance to major production constraints and interspecific lines deployed. Elucidation of plant mechanisms governing pest and disease resistance, abiotic stress tolerance and grain nutritional quality guides the selection methods used by the breeders. Molecular markers are used to select for resistance to key diseases and insect pests. Efforts have been made to utilize modern genomic tools to increase scale, efficiency, accuracy and speed of breeding. Through gender-responsive participatory variety selection, market-demanded varieties have been released in several African countries. These new bean varieties are a key component of sustainable food systems in the tropics. K E Y W O R D S breeding tools, common bean, demand-led, micronutrient content, production constraints 1 | INTRODUCTION Common bean (Phaseolus vulgaris L.) is grown on about 30 million hectares globally and on 7.6 million ha in Africa annually where it is consumed and traded by more than 100 million households (Buruchara et al., 2011; FAOSTAT, 2014). Being a major staple, common bean contributes to health, food and nutritional security as it is wellendowed with starch, protein, fibre and minerals such as iron, zinc, potassium, selenium, molybdenum and vitamins (thiamine, vitamin B6) and folate. It is an ideal crop for the smallholder farming systems due to its capability to fix N, short maturity period (≤3 months), easily converted to cash to meet urgent household needs, relatively long storage and convenience of handling the harvest and its compatibility with other crops (maize, cassava, banana, etc.), in many low-input production systems. Three East African countries, Kenya, Tanzania and Uganda, are among the global leaders of common bean production (Akibode & Maredia, 2011; FAOSTAT, 2016). The per capita consumption of 40-60 kg/year in Rwanda, Kenya and Uganda is the highest in the world (Beebe, Rao, Blair, & Acosta-Gallegos, 2013; Broughton et al., 2003). A unique partnership model involving CIAT and its research partners, together with effective breeding and seed delivery strategies, have helped to reach millions of beneficiaries with improved bean varieties (Buruchara et al., 2011). There is a notable increase in bean production in most African countries in the
Genetic diversity of common bean accessions in the germplasm bank of the Instituto Agronômico–IAC
2005
The genetic divergence among 993 accessions of common bean (Phaseolus vulgaris L.) in the germplasm bank of the Instituto Agronômico IAC (agronomical Institute in Campinas, state of São Paulo) was evaluated in an analysis using 23 qualitative and quantitative agromorphological/ morphological and agronomic descriptors. Multivariate analyses such as the Euclidean distance, principal component analysis and Tocher's cluster method were used to quantify the divergence among the accessions. The joint use of the analyses allowed the identification of 45 groups of which the first five absorbed 88.28% of all accessions. Among the 23 evaluated descriptors, the principal component analysis allowed the discarding of five that were redundant and/or little variable and the eight first principal components were necessary to explain 70% of the total variation. The multivariate methods proved efficient when used in germplasm collections, optimizing the descriptor set and establishing an orientation for future crossings in the common bean improvement program of the IAC.