Common Bean Germplasm Research Articles

Allelic Diversity, Structural Analysis, and Genome-Wide Association Study (GWAS) for Yield and Related Traits Using Unexplored Common Bean (Phaseolus vulgaris L.) Germplasm From Western Himalayas.

The north-western Indian Himalayas possesses vast diversity in common bean germplasm due to several years of natural adaptation and farmer’s selection. Systematic efforts have been made for the first time for the characterization and use of this huge diversity for the identification of genes/quantitative trait loci (QTLs) for yield and yield-contributing traits in common bean in India. A core set of 96 diverse common bean genotypes was characterized using 91 genome-wide genomic and genic simple sequence repeat (SSR) markers. The study of genetic diversity led to the identification of 691 alleles ranging from 2 to 21 with an average of 7.59 alleles/locus. The gene diversity (expected heterozygosity, He) varied from 0.31 to 0.93 with an average of 0.73. As expected, the genic SSR markers detected less allelic diversity than the random genomic SSR markers. The traditional clustering and Bayesian clustering (structural analysis) analyses led to a clear cut separation of a core set of 96 genotypes into two distinct groups based on their gene pools (Mesoamerican and Andean genotypes). Genome-wide association mapping for pods/plant, seeds/pod, seed weight, and yield/plant led to the identification of 39 significant marker–trait associations (MTAs) including 15 major, 15 stable, and 13 both major and stable MTAs. Out of 39 MTAs detected, 29 were new MTAs reported for the first time, whereas the remaining 10 MTAs were already identified in earlier studies and therefore declared as validation of earlier results. A set of seven markers was such, which were found to be associated with multiple (two to four) different traits. The important MTAs will be used for common bean molecular breeding programs worldwide for enhancing common bean yield.

Analysis of the genetic diversity of grain legume germplasm resources in China and the development of universal SSR primers

The research objects of this paper are Vigna angularis, Vigna radiata and Phaseolus vulgaris, which are important grain legume resources in China. However, the genetic structure between the three species is not clear. Therefore, this study developed a set of universal gSSR (simple sequence repeat) primers based on the whole-genome sequences of adzuki beans, mung beans and common beans and analysed the genetic diversity of the test resources based on universal gSSR loci. A total of 53,099 pairs of universal primers were developed, and 43 universal primer pairs were selected for analysis of their test resources. The genetic diversity of the tested common bean germplasm resources was the largest, and the genetic diversity of the tested mung bean germplasm resources was the smallest. Based on the structural analysis and NJ algorithm, the genetic relationships of the test resources were analysed. When ΔK = 3, 3 and 2, the test resources were divided into 3, 3 and 2 subgroups, respectively. The average genetic differentiation coefficient among the three species was 0.24, and the average gene flow value was 0.78. The genetic distances among the three species ranged from 0.27 to 0.90. The genetic distance between the tested adzuki bean germplasm resources and the tested mung bean germplasm resources was the closest, and the genetic distance between the test adzuki bean germplasm resources and the tested common bean germplasm resources was the farthest. This study provides a scientific basis for the rational development, protection and sustainable use of germplasm resources.

Differential Regulation of Drought Responses in Two Phaseolus vulgaris Genotypes.

Drought is probably the most harmful stress affecting common bean crops. Domestication, worldwide spread and local farming practices has entailed the development of a wide variety of common bean genotypes with different degrees of resistance to water stress. In this work, physiological and molecular responses to water stress have been compared in two common bean accessions, PHA-0683 and PMB-0220, previously identified as highly and moderately resistant to water stress, respectively. Our hypothesis was that only quantitative differences in the expression patterns of key genes should be found if molecular mechanisms regulating drought resistance are similar in the two accessions. However, results presented here indicate that the resistance to drought in PMB-0220 and PHA-0683 common bean accessions is regulated by different molecular mechanisms. Differential regulation of ABA synthesis and ABA signaling related genes among the two genotypes, and the control of the drought-induced senescence have a relevant contribution to the higher resistance level of PHA-0683 accession. Our results also suggest that expression patterns of key senescence-related transcription factors could be considered in the screening for drought resistance in common bean germplasm collections.

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.

Genome-Wide Association Studies Detect Multiple QTLs for Productivity in Mesoamerican Diversity Panel of Common Bean Under Drought Stress.

Drought stress is an important abiotic factor limiting common bean yield, with great impact on the production worldwide. Understanding the genetic basis regulating beans’ yield and seed weight (SW) is a fundamental prerequisite for the development of superior cultivars. The main objectives of this work were to conduct genome-wide marker discovery by genotyping a Mesoamerican panel of common bean germplasm, containing cultivated and landrace accessions of broad origin, followed by the identification of genomic regions associated with productivity under two water regimes using different genome-wide association study (GWAS) approaches. A total of 11,870 markers were genotyped for the 339 genotypes, of which 3,213 were SilicoDArT and 8,657 SNPs derived from DArT and CaptureSeq. The estimated linkage disequilibrium extension, corrected for structure and relatedness (r2sv), was 98.63 and 124.18 kb for landraces and breeding lines, respectively. Germplasm was structured into landraces and lines/cultivars. We carried out GWASs for 100-SW and yield in field environments with and without water stress for 3 consecutive years, using single-, segment-, and gene-based models. Higher number of associations at high stringency was identified for the SW trait under irrigation, totaling ∼185 QTLs for both single- and segment-based, whereas gene-based GWASs showed ∼220 genomic regions containing ∼650 genes. For SW under drought, 18 QTLs were identified for single- and segment-based and 35 genes by gene-based GWASs. For yield, under irrigation, 25 associations were identified, whereas under drought the total was 10 using both approaches. In addition to the consistent associations detected across experiments, these GWAS approaches provided important complementary QTL information (∼221 QTLs; 650 genes; r2 from 0.01% to 32%). Several QTLs were mined within or near candidate genes playing significant role in productivity, providing better understanding of the genetic mechanisms underlying these traits and making available molecular tools to be used in marker-assisted breeding. The findings also allowed the identification of genetic material (germplasm) with better yield performance under drought, promising to a common bean breeding program. Finally, the availability of this highly diverse Mesoamerican panel is of great scientific value for the analysis of any relevant traits in common bean.

Diversity of nutritional content in seeds of Brazilian common bean germplasm.

Mineral deficiency is worldwide one of the major problems associated with human health, and biofortification through breeding is considered an important strategy to improve the nutritional content of staple food in countries that face this problem. The assessment of genetic variability for seed nutrient contents is a first step in the development of a biofortified crop. From the germplasm bank IDR-IAPAR-EMATER, a set of 1,512 common bean accessions, consisting of local and commercial varieties and improved lines, was analyzed. High variability among the accessions was observed for all evaluated nutrient contents (P, K, Ca, Mg, Cu, Zn, Mn, Fe and S and protein). In the mean, the contents of the carioca and black market groups (Mesoamerican gene pool), were around 7% higher for the minerals Ca, Cu, Mn and Fe and between 2-4% higher for P, K, Mg and Zn than in the other groups with Mesoamerican and Andean common bean. Few differences were observed among the Mesoamerican accessions that belong to the carioca and black commercial groups. Wide variability was observed among the evaluated genotypes, and the concentrations of the best accessions exceeded the overall mean by 14-28%. Due to the high variability in the evaluated accessions, these results may contribute to the selection of promising parents for the establishment of mating blocks. The nutritional contents of many of the improved lines evaluated in this study were higher than those of the commercial cultivars, indicating the possibility of developing new biofortified cultivars.

Preserving Biodiversity in Marginal Rural Areas: Assessment of Morphological and Genetic Variability of a Sicilian Common Bean Germplasm Collection.

The historical cultivation of common bean (Phaseolus vulgaris L.) has resulted in the development of local populations/cultivars in restricted Italian rural areas. Many common bean landraces, still cultivated in small mountain areas from Sicily, have become outdated and endangered due to the commercial varieties spreading. These accessions are poorly known but often represent a genetic heritage to be preserved and enhanced. The ex situ conservation of fifty-seven Sicilian common bean landraces was carried out at the “Living Plants Germplasm Bank” at Ucria (Messina, Italy), founded by the Nebrodi Regional Park, together with the “Sicilian Plant Germplasm Repository” of University of Palermo (SPGR/PA). To assess the germplasm genetic diversity, nineteen morphological traits and eight Simple Sequence Repeats (SSRs) were used. Genetic distances among landraces were calculated to construct a clustering tree by using unweighted pair group method arithmetic (UPGMA). Seed germplasm diversity of Sicilian common bean varied from 80.7% to 93.3%, based on six seed descriptors and six leaf, flower, and pod descriptors, respectively, while cluster genetic analysis depicted a clear separation among all the 57 landraces. Principal coordinates (PCoA) and STRUCTURE analyses showed a prevalent rate of admixture between Mesoamerican and Andean gene pools in Sicilian common bean collection, confirming its heterogeneity. The observed high level of diversity evidenced the needs to adopt accurate criterion to plan a definitive ex situ germplasm collection to share agrobiodiversity with local farmers and to avoid any further loss of genetic resources in rural and protected areas.

Genetic Diversity of Common Bean (Phaseolus vulgaris L.) Germplasm Resources in Chongqing, Evidenced by Morphological Characterization

In this study, the genetic diversity of 115 common bean germplasm resources collected from 27 counties in Chongqing over 3 years (2015–2017) was assessed. The results showed that the genetic diversity of the common bean germplasm resources was high, with an average diversity index of 1.447. The diversity of the qualitative traits of each organ was ranked as seed (H′ = 1.40) > pod (H′ = 1.062) > plant (H′ = 0.64) > leaf (H′ = 0.565), while the diversity of the quantitative traits of each organ was ranked as seed (H′ = 2.021) > pod (H′ = 1.989) > phenology (H′ = 1.941) > plant (H′ = 1.646). In the cluster analysis, 115 accessions were clustered into four groups. The accessions in the first and fourth group were characteristic of the Andean gene pool, while the accessions in the second group were characteristic of the Mesoamerican gene pool. However, the accessions of the third group possessed the combined characteristics of both gene pools and were thus classified as introgressed type. Four principal components represented 40.30% of the morphological diversity, with the first principal component representing the traits associated with plant growth; the second principal component representing flower characteristics; the third principal component being composed of seed characters; and the fourth principal component representing pod characteristics. The common bean germplasm resources are widely distributed in Chongqing, and the introgressed types are more prevalent in this region than elsewhere, with a rich genetic diversity and high utilization value in genetic breeding.

Origin and diversity study of local common bean (Phaseolus vulgaris L.) germplasm from Serbia: phaseolin and phenotyping approach

Phenotypic diversity of common bean (Phaseolus vulgaris L.) landraces and reference cultivars were evaluated based on variability of twelve traits, chosen according to international descriptor list. Landraces were collected form 53 locations in Republic of Serbia. Origin and dissemination of local common bean germplasm was assessed based on variation of phaseolin types. Phaseolin analysis showed that landraces of both Mesoamerican and Andean origin are grown in Serbia, with higher frequency of Andean types. Ratio of three phaseolin types found in studied common bean germplasm suggested its introduction in Serbia from northern borders. Shannon–Weaver index was used as indicator of phenotypic diversity, showing high diversity level among studied germplasm. HOMALS analysis was performed in order to determine discriminative power of traits and structure of studied germplasm. Seed and flower traits, as well as growth habit type had highest, opposed to phaseolin type with lowest discriminative power among genotypes. Genotypes were phenotypically individualized and classified in five homogenous groups according to their profiles, displaying differentiation on the gene pool level, as well.

Genetic diversity analysis of common bean (Phaseolus vulgaris L.) genotypes for resistance to Mexican bean weevil (Zabrotes subfasciatus), using single nucleotide polymorphism and phenotypic markers

ABSTRACT The objective of this study was to examine the genetic diversity present among 297 common bean genotypes using 2554 SNPs and 12 insects and seed-related traits. The phenotyping was done under laboratory condition while the genotyping was conducted by using the Illumina SNP BeadChip. High phenotypic diversity among traits were recorded, ranging from 0.87 to 0.96, with a mean of 0.92. Principal component and discriminant analyses identified four PCs and three discriminant functions, which explained 82% and 100% of the total phenotypic variations among genotypes, respectively. Polymorphic Information Content ranged from 0.21 to 0.38, with a mean of 0.34. The mean gene diversity among genotypes ranged from 0.24 to 0.50, with a mean of 0.44. Genetic distance ranged from 0.19 to 0.82, with a mean of 0.62, while the phenotypic distance ranged from 0.00 to 1.00, with a mean of 0.64 were observed aamong genotypes. The analysis of molecular variance revealed highly significant differences (p<0.001) among and within individuals and among populations. Both the SNP and the phenotypic markers grouped the 297 genotypes into two major distinct clusters and three sub-clusters. This information is useful for identification and development of common bean germplasm with economically valuable traits and the conservation and utilization of genotypes.

Investigation of Quality and Cooking Traits Diversity in a Global Common Bean Germplasm

Common bean is a nutrient?dense food legume serving a source of food for millions of people all over the world. Quality and cooking traits are considered important criteria for the success and appealability of any crop cultivars to the end-users. In this study, we aimed to explore the cooking and quality-related traits diversity in a world common bean germplasm originated from 10 countries of world. A good range of variations were observed for all studied traits and mean fat, starch and fiber contents were 1.65 %, 42.96% and 9.23%, respectively. Genotype-140 reflected higher swelling capacity, swelling index, hydration capacity, hydration index, seed density and lesser cooking time. Correlation analysis was performed and hydration capacity showed highly significant and positive correlation with hydration index, swelling capacity and swelling index. Principal component analysis (PCA) was performed and 1st five PCs accounted a total of 78.14% variations. Biplot analysis resulted a total of 51.01% variations and studied germplasm was divided on the basis of cooking and quality traits. Constellation plot divided the studied germplasm into two main clustered A and B on the basis of moisture, swelling capacity, seed density and cooking time. Genotype-39 and genotype-20 were found distant for fat contents, while genotype-24 and genotype-120 for starch contents. Therefore, these genotypes are recommended as parents for common bean breeding regarding fat and starch contents. Moreover, genotype-140 showed minimum cooking time, it should be also used as a candidate parent to develop common bean cultivars requiring lesser cooking time to save time and energy. We believe that results presented herein will be very helpful for common bean breeding community interested in quality and cooking traits.

Genetic Diversity in Common Bean (Phaseolus vulgaris L.) Germplasm to Establish a Breeding Program in the Mountainous Region of Jammu and Kashmir

Common bean (Phaseolus vulgaris L.) is native to Middle America and Andean mountains of South America. Due to its nutritious value, it is one of the most important legume crop of the world. Evaluation of genetic diversity of a crop is extremely important for the establishment of a breeding program and selection of varieties for cultivation. We evaluated the genetic diversity and phylogenetic relationship of 40 P. vulgaris ecotypes from CIAT (International Center for Tropical Agriculture) germplasm using seed protein profiles produced by sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE), to screen the germplasm to be used in a breeding program. A total of 21 bands scored 14 were found polymorphic. A distance matrix was generated from the similarity matrix based on polymorphic bands. The UPGMA tree was established through cluster analysis performed on the distance matrix. Six major clusters were formed on the basis of SDS_PAGE analysis with one ecotype (E13-G16832) being the most diverse. This analysis provided the basis for selection of suitable ecotypes to be used in the establishment of a breeding program.ane damage the leaves helped the tolerant genotypes to sustain under salinity stress in a better way than the susceptible genotypes.

Screening and identification of resistant sources against Sclerotinia sclerotiorum causing white mold disease in common bean

AbstractWhite mold caused by Sclerotinia sclerotiorum (Lib.) de Bary is a devastating constraint in common bean (Phaseolus vulgaris L.) production, affecting plants at both seedling and adult stages. Being a crop of small‐area, resource‐poor, farmers and given the high cost of fungicides, farmers prefer the use of region‐specific landraces or resistant accessions. In this study, we compared various methods of bean plant inoculation with S. sclerotiorum and found modified straw test method of inoculation as most accurate and effective. Using this method, we screened a panel of 516 common bean germplasm procured from 22 countries through the National Bureau of Plant Genetic Resources (NBPGR; New Delhi, India) against white mold pathogen. Only 12 accessions were found resistant, whereas 121 were moderately resistant to white mold. Among exotic resistant accessions, EC271515, EC271475, EC271523, and EC271528 were from the Colombian region, while the remaining four, EC530910, EC530913, EC530916, and EC531044, belonged to Columbia. Of the four resistant landraces from India, IC280353 was a collection from Jammu and Kashmir State, whereas landraces IC278744, IC278709, and IC278734 were from Himachal Pradesh. Considering the area under disease progress curve (AUDPC), incubation period, infection rate, and lesion length, EC‐271475 followed by EC‐530916 were concluded to be the best accessions against white mold. Further, the statistical analysis also confirms the highly resistant nature of phenotypically screened common bean accessions. One exotic accession, EC271475, possessing resistance to S. sclerotiorum was also resistant to bean common mosaic virus (BCMV) strain NL‐7n and could be used in common bean breeding programs.

On-farm multi-location evaluation of genotype by environment interactions for seed yield and cooking time in common bean

Common bean variety choice by farmers in Uganda is driven by seed yield plus end-use quality traits like market class and cooking time. Limited genotype by environment information is available for traits valued by consumers. This research evaluated yield, seed size, hydration properties, and cooking time of 15 common bean genotypes within market classes recognized by consumers along with three farmers’ checks at nine on-farm locations in Uganda for two seasons. Yield ranged from 71 to 3,216 kg ha−1 and was largely controlled by location (21.5% of Total Sums of Squares [TSS]), plus the interaction between location and season (48.6% of TSS). Cooking time varied from 19 to 271 minutes with the genotypes Cebo Cela and Ervilha consistently cooking fastest in 24 and 27 minutes respectively. Comparatively, the local checks (NABE-4, NABE-15, and Masindi yellow) took 35 to 45 minutes to cook. Cooking time was largely controlled by genotype (40.6% of TSS). A GGE biplot analysis uncovered the presence of two mega-environments for yield and one mega-environment for cooking time. Identification of mega-environments for these traits will help expedite common bean breeding, evaluation, and variety selection through reduction of number of test environments needed for phenotype evaluations. The high yielding and fast cooking genotypes from this study can be targeted as parental materials to improve existing common bean germplasm for these important traits.

Natural Variation in Portuguese Common Bean Germplasm Reveals New Sources of Resistance Against Fusarium oxysporum f. sp. phaseoli and Resistance-Associated Candidate Genes.

Common bean (Phaseolus vulgaris) is one of the most consumed legume crops in the world, and Fusarium wilt, caused by the fungus Fusarium oxysporum f. sp. phaseoli, is one of the major diseases affecting its production. Portugal holds a very promising common bean germplasm with an admixed genetic background that may reveal novel genetic resistance combinations between the original Andean and Mesoamerican gene pools. To identify new sources of Fusarium wilt resistance and detect resistance-associated single-nucleotide polymorphisms (SNPs), we explored, for the first time, a diverse collection of the underused Portuguese common bean germplasm by using genome-wide association analyses. The collection was evaluated for Fusarium wilt resistance under growth chamber conditions, with the highly virulent F. oxysporum f. sp. phaseoli strain FOP-SP1 race 6. Fourteen of the 162 Portuguese accessions evaluated were highly resistant and 71 intermediate. The same collection was genotyped with DNA sequencing arrays, and SNP-resistance associations were tested via a mixed linear model accounting for the genetic relatedness between accessions. The results from the association mapping revealed nine SNPs associated with resistance on chromosomes Pv04, Pv05, Pv07, and Pv08, indicating that Fusarium wilt resistance is under oligogenic control. Putative candidate genes related to phytoalexin biosynthesis, hypersensitive response, and plant primary metabolism were identified. The results reported here highlight the importance of exploring underused germplasm for new sources of resistance and provide new genomic targets for the development of functional markers to support selection in future disease resistance breeding programs.

Evaluation of Common Bean Germplasm Lines for Resistance to Angular Leaf Spot (Phaeoisariopsis griseola (Scac.) Ferraris) Under High Altitude Conditions of Gurez Valley

During kharif season of years 2017 and 2018 field screening of sixteen common bean germplasm lines against angular leaf spot (ALS) under natural disease epidemic conditions could identify for resistance to angular leaf spot (ALS) in common bean have relied on a range of sources of resistance. However, due to occurrences of many different races of the pathogen, sources of resistance may not always be effective in all the regions. The present study was conducted to identify new sources of resistance to ALS. A total of sixteen new germplasm lines were evaluated for resistance. The results observed that the response germplasm lines to ALS during the two years were similar. The results further revealed that under epiphytic conditions only one germplasm viz., SR-1 exhibited resistance reaction.

Diversification and genetic structure of the western-to-eastern progression of European Phaseolus vulgaris L. germplasm

BackgroundCommon bean (Phaseolus vulgaris L.) is the most important food legume for direct human consumption around the world, as it represents a valuable source of components with nutritional and health benefits.ResultsWe conducted a study to define and explain the genetic relatedness and diversification level of common bean (Phaseolus vulgaris L.) germplasm from Portugal to Ukraine, along a western-to-eastern line of southern European countries, including Poland. This was based on the P. vulgaris genetic structure, and was designed to better describe its distribution and domestication pathways in Europe. Using the multi-crop passport descriptors that include geographic origin and different phaseolin types (corresponding to the Mesoamerican and Andean gene pools), 782 accessions were obtained from nine gene banks and 12 geographic origins. We selected 33 genome/ gene-related/ gene-pool-related nuclear simple sequence repeat markers that covered the genetic diversity across the P. vulgaris genome. The overall polymorphic information content was 0.800. Without specifying geographic origin, global structure cluster analysis generated 10 genetic clusters. Among the PvSHP1 markers, the most informative for gene pool assignment of the European P. vulgaris germplasm was PvSHP1-B. Results of AMOVA show that 89% of the molecular variability is shared within the 782 accessions, with 4% molecular variability among the different geographic origins along this western-to-eastern line of southern Europe (including Poland).ConclusionsThis study shows that the diversification line of the European P. vulgaris germplasm followed from the western areas of southern Europe (Portugal, Spain, Italy, Slovenia) to the more eastern areas of southern Europe. This progression defines three geographically separated subgroups, as the northern (Poland, Ukraine, Romania), southern (Albania, Bulgaria), and central (Bosnia and Herzegovina, Serbia, Hungary) areas of eastern Europe.

Higher Effectiveness of New Common Bean (Phaseolus vulgaris L.) Germplasm Acquisition by Collecting Expeditions Associated with Molecular Analyses

A remarkable portion of crop genetic diversity is represented by landraces and obsolete cultivars, that have not yet been integrated into the collections of genetic resources in genebanks. Fortunately, they are still maintained by small farmers in rural areas. Their acquisition is an important goal for collecting expeditions, followed by the evaluation of their genetic background. Molecular markers are powerful tools to evaluate the effectiveness of acquisition of new genetic variants. This approach was used for common bean landraces, that were collected through expeditions in the Slovak and Ukrainian Carpathians. In this study, microsatellite markers, developed from expressed sequence tags, were used for genotyping the collected materials. The sub-population of collected landraces contained higher total and average number of different alleles in comparison to equally large sub-populations of already-maintained cultivars. The same was true for the Shannon’s information index, observed heterozygosity, and expected heterozygosity. Both sub-populations showed the presence of private alleles: Average values of 0.500 and 0.833 private alleles per genotype were detected in landraces, and cultivars, respectively. Obtained results emphasized the importance of collecting expeditions to specific regions where landraces are cultivated, even at the present time. The effectiveness of the acquisition of new genetic variability can be determined by molecular tools, as confirmed by microsatellite markers in this study.

Genetic Diversity and Population Structure of Kenyan Common Bean (Phaseolus vulgaris L.) Germplasm Using Peroxidase Gene Markers

Common bean (Phaseolus vulgaris L.) is a vital legume used as human food, source of cash income, feed for livestock, and it increases the fertility of soil by its ability to fix nitrogen. The aim of this research was to determine the genetic diversity and population structure of 40 common bean germplasm cultivated in Kenya, using peroxidase gene (POX)-based molecular markers. The loci analyzed showed high diversity and amplified 624 alleles, ranging from 3 to 9 on every locus, with an average of 7.20. The PIC of the POX markers varied from 0.6204 to 0.9110, with an average of 0.7677. The range of the observed heterozygosity was from 0.6667 to 0.9150 with a mean of 0.7945, while the values of the mean genetic diversity ranged from 0.3072 to 0.4425 with a mean of 0.3972. The UPGMA phenogram separated the genotypes into two main genetic clusters, and the genotypes showed no grouping by geographical origins. The highest value of genetic variation was observed between the genotypes obtained from Western, Rift valley and Central regions of Kenya. Population structure analysis grouped the germplasm into 7 gene pools and showed that the genotypes have a common genetic lineage. AMOVA revealed higher genetic diversity (99%) within population than among population (1%), and this offers a reliable base for the design of genetic improvement schemes. Results of the present study can be used in future breeding programs and for the genetic improvement in common bean.

Screening Common Bean (Phaseolus vulgaris L.) Germplasm for Resistance against Angular Leaf Spot (Pseudocercospora griseola) Disease under Field Condition

Angular leaf spot (ALS) caused by the fungus Pseudocercospora griseola is one of the most destructive disease in Latin America and eastern Africa countries. The fungus, P. griseola is highly variable and a diverse sources of resistance genes is required to manage this economically important disease. The use of genetic resistance is the most practical and economic way to manage angular leaf spot of the common bean. Common bean (Phaseolus vulgarise L.) germplasm were screened for resistance against Angular leaf spot (ALS) under field conditions at Wonodogenet and Areka Research farms. Out of 300 common bean accessions evaluated only 14 (4.6%) common bean accessions were resistant to naturally epidemics of angular leaf spot disease under field condition. Therefore, all common bean germplasm that showed resistance reaction can be involved in breeding program for the improvement of the common bean.