Common Bean Germplasm Research Articles

SNP discovery in common bean by restriction-associated DNA (RAD) sequencing for genetic diversity and population structure analysis.

Researchers have made great advances into the development and application of genomic approaches for common beans, creating opportunities to driving more real and applicable strategies for sustainable management of the genetic resource towards plant breeding. This work provides useful polymorphic single-nucleotide polymorphisms (SNPs) for high-throughput common bean genotyping developed by RAD (restriction site-associated DNA) sequencing. The RAD tags were generated from DNA pooled from 12 common bean genotypes, including breeding lines of different gene pools and market classes. The aligned sequences identified 23,748 putative RAD-SNPs, of which 3357 were adequate for genotyping; 1032 RAD-SNPs with the highest ADT (assay design tool) score are presented in this article. The RAD-SNPs were structurally annotated in different coding (47.00%) and non-coding (53.00%) sequence components of genes. A subset of 384 RAD-SNPs with broad genome distribution was used to genotype a diverse panel of 95 common bean germplasms and revealed a successful amplification rate of 96.6%, showing 73% of polymorphic SNPs within the Andean group and 83% in the Mesoamerican group. A slightly increased He (0.161, n=21) value was estimated for the Andean gene pool, compared to the Mesoamerican group (0.156, n=74). For the linkage disequilibrium (LD) analysis, from a group of 580 SNPs (289 RAD-SNPs and 291 BARC-SNPs) genotyped for the same set of genotypes, 70.2% were in LD, decreasing to 0.10%in the Andean group and 0.77% in the Mesoamerican group. Haplotype patterns spanning 310Mb of the genome (60%) were characterized in samples from different origins. However, the haplotype frameworks were under-represented for the Andean (7.85%) and Mesoamerican (5.55%) gene pools separately. In conclusion, RAD sequencing allowed the discovery of hundreds of useful SNPs for broad genetic analysis of common bean germplasm. From now, this approach provides an excellent panel of molecular tools for whole genome analysis, allowing integrating and better exploring the common bean breeding practices.

Genetic diversity of common bean accessions from former Yugoslav Republic of Macedonia as revealed by molecular and morphological markers

Cultivation of common bean has a long tradition in the Former Yugoslav Republic of Macedonia (FYROM) and is still nowadays important part of the human diet. In a study reported here 71 accessions from the FYROM were assessed for genetic diversity with the aim to provide information on genetic structure of Macedonian common bean germplasm and to depict its peculiarities. A total of 71 accessions were assessed using 13 microsatellite and 16 morphological markers. The average number of alleles per microsatellite was 5.8, and ranged from three to 16 alleles. High capacity of selected markers for distinguishing genotypes was identified by the calculation of a very low value of probability of identity. The relationship among 71 studied accessions was assessed by hierarchical cluster analysis. A very clear separation of accessions into two groups was observed in the UPGMA dendrogram. The larger represented Andean gene pool and contained 40 accessions (56% of total), while the other 31 accessions (44% of total) composed Mesoamerican gene pool. The two groups were successfully discriminated by eight morphological traits. Within the larger Andean cluster in the UPGMA dendrogram a sub-group of 16 climbing accessions was separated from 24 bush accessions. The absence of the string in the pods of the climbers suggests that this sub-group comprises snap beans grown primarily for their fresh pods. There were eight morphological traits in total that distinguished the two Andean sub-groups. Assessment of genetic relationship among accessions, their classification into respective gene pool and identification of morphological peculiarities provided valuable information for the management of plant gene bank and Macedonian bean breeding program.

Reaction of selected common bean germplasm accessions to bacterial brown spot in South Africa

Bacterial brown spot (BBS), caused by Pseudomonas syringae pv. syringae (Pss), is a disease of common beans (Phaseolus vulgaris L.) in South Africa. Planting of pathogen-free seed and application of copper-based chemicals do not guarantee disease control. Genetic resistance is considered the most effective control measure. BBS occurs regularly in major dry bean production areas. The aim of this study was to screen selected accessions for their reaction to BBS. Twenty-seven common bean accessions were assessed over three seasons and locations for resistance to BBS. Trials were arranged in a randomized complete block design with three replications and artificially inoculated with Pss (1 × 108 CFU/mL) using a Stihl mistblower at 21, 28 and 36 days after planting. Plots were rated for disease reaction on a modified 1–9 CIAT scale with 1 being resistant and 9 being susceptible. Ratings were done at 7, 14, 21 and 28 days after the first inoculation. Trials were harvested manually and yield data were recorded. Disease ratings were used to construct the area under the disease progress curve (AUDPC). Highly significant genotype × environment interactions were recorded and additive main effects and multiplicative interaction analysis was used to identify lines in which disease response and yield were significantly affected by environment. VAX 4 and VAX 2 had lowest disease ratings of 1.8 and 2.0, and AUDPC values of 38.6 and 41.6, respectively, and are therefore potential resistance sources.

Mejoramiento genético de frijol tipo Andino para Panamá: Resultados de un proyecto de PROFRIJOL. 1993-1996.

Native germplasm of a Panama common bean was evaluated in order to obtain its morphologic characteristics and compare them with a group of lines and varieties of CIAT’s breeding program. The purpose was to find a germplasm that could surpass native varieties in terms of its resistance to Web Blight, yield, growing habits, and grain color. A randomized complete block design was used. Five promising lines for commercial use were selected based on yield, resistance to Web Blight, growth pattern, and grain color criteria. Three bean lines are undergoing validation trials in farms.

Fine-mapping of a major QTL controlling angular leaf spot resistance in common bean (Phaseolus vulgaris L.).

Key message A major QTL for angular leaf spot resistance in the common bean accession G5686 was fine-mapped to a region containing 36 candidate genes. Markers have been developed for marker-assisted selection. Common bean (Phaseolus vulgaris L.) is an important grain legume and an essential protein source for human nutrition in developing countries. Angular leaf spot (ALS) caused by the pathogen Pseudocercospora griseola (Sacc.) Crous and U. Braun is responsible for severe yield losses of up to 80 %. Breeding for resistant cultivars is the most ecological and economical means to control ALS and is particularly important for yield stability in low-input agriculture. Here, we report on a fine-mapping approach of a major quantitative trait locus (QTL) ALS4.1GS, UC for ALS resistance in a mapping population derived from the resistant genotype G5686 and the susceptible cultivar Sprite. 180 F3 individuals of the mapping population were evaluated for ALS resistance and genotyped with 22 markers distributed over 11 genome regions colocating with previously reported QTL for ALS resistance. Multiple QTL analysis identified three QTL regions, including one major QTL on chromosome Pv04 at 43.7 Mbp explaining over 75 % of the observed variation for ALS resistance. Additional evaluation of 153 F4, 89 BC1F2 and 139 F4/F5/BC1F3 descendants with markers in the region of the major QTL delimited the region to 418 kbp harboring 36 candidate genes. Among these, 11 serine/threonine protein kinases arranged in a repetitive array constitute promising candidate genes for controlling ALS resistance. Single nucleotide polymorphism markers cosegregating with the major QTL for ALS resistance have been developed and constitute the basis for marker-assisted introgression of ALS resistance into advanced breeding germplasm of common bean.Electronic supplementary materialThe online version of this article (doi:10.1007/s00122-015-2472-6) contains supplementary material, which is available to authorized users.

Characterisation of 4274 accessions of common bean (Phaseolus vulgaris L.) germplasm conserved in the Indian gene bank for phenological, morphological and agricultural traits

Common bean is one of the most impor- tant legume crops worldwide. Response to selection and success of hybridisation in common bean pri- marily depends on the nature and magnitude of genetic diversity present in the germplasm used. Germplasm comprising 4274 accessions originating from 58 countries were characterized for 22 phenotypic traits for two years. Genetic diversity for traits such as leaf length (4.5-20.7 cm), leaf width (3.4-17.5 cm), pod length (PL) (3.5-23.5 cm), no of pods/plant (4.2-59.6), seeds/pod (2.1-9.6) and 100-seed weight (SWT) (3.5-96.3 g) was observed in the accessions. Based on multivariate analysis, the entire collection was grouped into 10 genetically diverse clusters irrespective of the origin or place of collection of accessions. First three components obtained through principal component analysis explained 80.44 % of the total variance and it was contributed mainly by PL, pod width (PW), seed length (SL), seed width (SW), pods/plant and SWT. Correlation coefficient of seed weight was positively significant with leaf length, PL, PW, SL and SW while it was negatively correlated with days to flowering, pods/plant and seeds/pod. Regression analysis showed highest direct effect of SW on seed weight followed by SL, and PL. For bean anthracnose, (600 accessions showed resistance un- der field conditions, however when subjected to screening under artificial conditions against four most prevalent races (03, 515, 598 and 529) of Col- letotrichum lindemutianum, we identified 16 acces- sions which have complete resistance and good agronomic superiority. These accessions may serve as useful genetic material to plant breeders for breeding bean varieties for anthracnose resistance and high yield.

English

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 cetyl-trimethylammonium 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 (FST) 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.   Key words: Phaseolin, Simple sequence repeat (SSR), hybridization, wrights fixation index (FST), structure.

Inheritance of resistance to the widely distributed race 6 ofPseudomonas syringaepv.phaseolicolain common bean pinto US14HBR6

Duncan, R. W., Gilbertson, R. L., Lema, M. and Singh, S. P. 2014. Inheritance of resistance to the widely distributed race 6 of Pseudomonas syringae pv. phaseolicola in common bean pinto US14HBR6. Can. J. Plant Sci. 94: 923–928. Halo blight disease of common bean (Phaseolus vulgaris L.) is caused by Pseudomonas syringae pv. phaseolicola (Psp) and is found worldwide in bean growing regions with temperate climates, such as the Midwestern United States. In situations where high levels of primary inoculum are present (e.g., in seed) and the climate is favorable, yield losses as high as 45% have been reported for susceptible cultivars. Disease resistance is the most desirable management strategy, and resistant cultivars and germplasm to some Psp races are available. However, high levels of resistance to Psp race 6, one of the most prevalent and economically important races, are not present in available cultivars. Here, we report the inheritance of a newly described source of resistance to Psp race 6 in the recently registered common bean pinto US14HBR6. The inheritance of resistance in US14HBR6 was investigated by making crosses between resistant (R) US14HBR6 and the susceptible (S) breeding line 92BG-7 and inoculating the parents, F1, F2, F3, and the respective backcrosses to either parent with Psp race 6. All 159 F1plants were susceptible, the F2segregated into 237S:16R and the F3segregated into 309S:26R. The US14HBR6*2×92BG-7 F1segregated into 83S:41R, and the US14HBR6×92BG-7*2 F1segregated into 116S:0R. Together, these results suggest that the resistance to Psp race 6 in US14HBR6 is controlled by two independently inherited recessive genes. Evidence is also presented that dominant alleles of these resistance genes, at one or both loci, contribute to dosage-dependent susceptibility to halo blight. These halo blight resistance genes can be used in the development of common bean germplasm and cultivars with high levels of resistance to Psp race 6. In combination with other race-specific and non-race specific resistance genes from diverse Phaseolus germplasm, these genes could also be used to generate germplasm lines and cultivars with resistance to all known races of Psp.

Comparative evaluation of common bean (Phaseolus vulgaris L.) germplasm for seed physical and culinary traits

Comparative evaluation of common bean (Phaseolus vulgaris L.) germplasm for seed physical and culinary traits

Comparison of inhibition of N2 fixation and ureide accumulation under water deficit in four common bean genotypes of contrasting drought tolerance

Drought is the principal constraint on world production of legume crops. There is considerable variability among genotypes in sensitivity of nitrogen fixation to drought, which has been related to accumulation of ureides in soybean. The aim of this study was to search for genotypic differences in drought sensitivity and ureide accumulation in common bean (Phaseolus vulgaris) germplasm that may be useful in the improvement of tolerance to water deficit in common bean. Changes in response to water deficit of nitrogen fixation rates, ureide content and the expression and activity of key enzymes for ureide metabolism were measured in four P. vulgaris genotypes differing in drought tolerance. A variable degree of drought-induced nitrogen fixation inhibition was found among the bean genotypes. In addition to inhibition of nitrogen fixation, there was accumulation of ureides in stems and leaves of sensitive and tolerant genotypes, although this was higher in the leaves of the most sensitive ones. In contrast, there was no accumulation of ureides in the nodules or roots of stressed plants. In addition, the level of ureides in the most sensitive genotype increased after inhibition of nitrogen fixation, suggesting that ureides originate in vegetative tissues as a response to water stress, probably mediated by the induction of allantoinase. Variability of drought-induced inhibition of nitrogen fixation among the P. vulgaris genotypes was accompanied by subsequent accumulation of ureides in stems and leaves, but not in nodules. The results indicate that shoot ureide accumulation after prolonged exposure to drought could not be the cause of inhibition of nitrogen fixation, as has been suggested in soybean. Instead, ureides seem to be produced as part of a general response to stress, and therefore higher accumulation might correspond to higher sensitivity to the stressful conditions.

Registration of a Small-Red Dry Bean Germplasm, TARS-LFR1, with Multiple Disease Resistance and Superior Performance in Low Nitrogen Soils

TARS-LFR1 (Reg. No. GP-292, PI 668258) is a multiple disease resistant common bean (Phaseolus vulgaris L.) germplasm developed through recurrent selection by the USDA–ARS, and by the University of Puerto Rico and Cornell University Agricultural Experiment Stations that has superior performance in low nitrogen (N) soils. Root rots, caused primarily by soil-borne fungi and Oomycetes, are important constraints to common bean production. These diseases are becoming a more serious problem under low-input, low-fertility, and climatic change conditions. In addition to root rot, this germplasm has resistance to common bacterial blight, caused by Xanthomonas axonopodis pv. phaseoli (Smith) Dye, and Bean common mosaic virus and yields well in association with rhizobia through biological nitrogen fixation. This combination of traits could play an important role in low-input and organic production systems. TARS-LFR1 has shown consistently high yield potential under root rot and low soil N conditions, and the use of this improved germplasm by breeding programs or in production zones affected by these stresses can potentially increase yield of common bean.

Response to Soil Acidity of Common Bean Genotypes (<i>Phaseolus vulgaris L</i>.) Under Field Conditions at Nedjo, Western Ethiopia

Soil acidity has become a serious threat to crop production in most highlands of Ethiopia in general and in the western part of the country in particular. A field experiment was conducted to evaluate soil acidity tolerant on 25 genotypes of common bean (Phaseolus vulgaris L.) on lime treated and untreated acid soils. The genotypes were evaluated based on morpho-agronomic parameters. Soil acidity had an effect on maturity, growth and yield of the tested genotypes. High significant(P<0.01) differences were observed among genotypes for days to maturity, leaf area index, plant height, number of pods per plant, pod length, hundred seed weight, grain yield, pod harvest index and harvest index in lime treated and untreated soils. Considerable variability exists among the genotypes tested based on the growth, and yield components measured for soil acidity tolerance. The genotypes gave higher yield and yield components when grown in lime treated soil than lime untreated with average yield reduction of 26% due to soil acidity effect. Relative grain yield was calculated as the ratio of grain yield in lime untreated to lime treated soil also showed higher significant differences among the tested genotypes. Genotypes such as Dimtu, new BILFA 58, Beshbesh, SER176, new BILFA51 and new BILFA 61 gave higher absolute and relative yield, whereas Dinknesh, Chore, Nasser and new BILFA 60 gave lower absolute grain and relative yield. Moreover, the great variability of 25 commonbean genotypes exhibited a good potential to screening large germplasm of common bean for soil acidity tolerance and develop a cultivar that are tolerant to soil acidity in the country. Keywords: Common bean, Genotypes, Lime, Soil acidity, Relative yield

Identification of resistance to rust (Uromyces appendiculatus) and powdery mildew (Erysiphe diffusa) in Portuguese common bean germplasm

AbstractPortugal has a diverse common bean germplasm, which is still grown in farmers' fields. In this work, we searched for resistance to rust (Uromyces appendiculatus) and powdery mildew (Erysiphe diffusa) in a representative collection of the Portuguese common bean germplasm. Despite many accessions depicting intermediate levels of resistance when compared to the susceptible check, 24 and 13 accessions showed low levels of infection, in spite of a compatible interaction (disease severity (DS) values lower than 5% and infection type (IT) of 4), to rust and powdery mildew, respectively, indicative of partial resistance. Moreover, a resistant reaction was observed in 11 accessions when inoculated with powdery mildew (IT = 0–1) and in additional 11 accessions (one in common) when inoculated with rust (IT = 0–2). The levels of resistance found in this report anticipate great potential of the Portuguese national germplasm, recently reported as genetically closer to the Andean common bean gene pool, for disease resistance breeding of this important crop.

Genetic diversity of two Indian common bean germplasm collections based on morphological and microsatellite markers

India is the second most populous nation in the world after China, and its plant genetic resources are an important basis for crop improvement to meet human population needs. An important legume in the diet of the Indian population is common bean (Phaseolus vulgarisL.). Common beans are one of the many important legumes grown in India, but unlike others, its centre of origin is not in Asia but in the Americas. The objective of this study was to evaluate two collections of Indian common beans: one for an internationally available collection of Food and Agriculture Organization (FAO)-protected accessions and one from the north-western Himalayan region. In total, 149 Indian landraces were evaluated with a total of 24 microsatellites across the two collections, and these represented all common bean-growing states of India. A population structure analysis was used to find groups in each collection, and this was compared across the collections. The genetic analysis of the two sets of Indian accessions with neighbour-joining trees and principal component analysis categorized the landraces into Andean and Mesoamerican gene pool groups. The Andean genotypes dominated the north-western Himalayan collection while the FAO-protected accessions were predominantly Mesoamerican. The Indian subcontinent can be considered as a region of high bean diversity; however, very little introgression was observed between the gene pools in both the germplasm sets. Gene pool identity was further substantiated by the comparison of seed traits, particularly seed size. The role of the landraces in plant breeding programmes is discussed.

Registration of TARS‐MST1 and SB‐DT1 Multiple‐Stress‐Tolerant Black Bean Germplasm

High‐ambient‐temperature stress, drought stress, root rot disease, and common bacterial blight [CBB; caused by Xanthomonas axonopodis pv. phaseoli (Smith) Dye] cause widespread yield reductions in common bean (Phaseolus vulgaris L.) worldwide. TARS‐MST1 (Reg. No. GP‐284, PI 661512) and SB‐DT1 (Reg. No. GP‐283, PI 661970) were developed by the USDA‐ARS, the University of Nebraska Agricultural Research Division, and the University of Puerto Rico Agricultural Experiment Station. These black bean lines were selected for tolerance to multiple stresses, including tolerance to high ambient temperature and drought. Specifically, both lines showed significantly higher yields under heat stress compared with the local check and had comparable yields to both heat‐ and drought‐tolerant controls under those stress conditions. TARS‐MST1 possesses resistance to CBB, and both lines are tolerant to root rot diseases. They incorporate exotic sources of stress tolerance, thus serving to diversify U.S. common bean germplasm. The lines were characterized for markers related to Bean common mosaic virus and CBB, and both lines carry the I gene, while TARS‐MST1 was positive for the presence of two CBB SCAR markers, SU91 and SAP6. The use of this germplasm in breeding programs can serve to improve the yield and stress tolerance of common bean.

SNP marker diversity in common bean (Phaseolus vulgaris L.)

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.

Biodiversity studies inPhaseolusspecies by DNA barcoding

The potential of DNA barcoding was tested as a system for studying genetic diversity and genetic traceability in bean germplasm. This technique was applied to several pure lines of Phaseolus vulgaris L. belonging to wild, domesticated, and cultivated common beans, along with some accessions of Phaseolus coccineus L., Phaseolus lunatus L., and Vigna unguiculata (L.) Walp. A multilocus approach was exploited using three chloroplast genic regions (rbcL, trnL, and matK), four intergenic spacers (rpoB-trnC, atpBrbcL, trnT-trnL, and psbA-trnH), and nuclear ITS1 and ITS2 rDNA sequences. Our main goals were to identify the markers and SNPs that show the best discriminant power at the variety level in common bean germplasm, to examine two methods (tree based versus character based) for biodiversity analysis and traceability assays, and to evaluate the overall utility of chloroplast DNA barcodes for reconstructing the origins of modern Italian varieties. Our results indicate that the neighbor-joining method is a powerful approach for comparing genetic diversity within plant species, but it is relatively uninformative for the genetic traceability of plant varieties. In contrast, the character-based method was able to identify several distinct haplotypes over all target regions corresponding to Mesoamerican or Andean accessions; Italian accessions originated from both gene pools. On the whole, our findings raise some concerns about the use of DNA barcoding for intraspecific genetic diversity studies in common beans and highlights its limitations for resolving genetic relationships between landraces and varieties.

Identification of QTL for agronomic traits and resistance to white mold in wild and landrace germplasm of common bean

With 1 figure and 5 tablesAbstractWhite mold, caused by Sclerotinia sclerotiorum (Lib.) De Bary, is a serious yield reducing fungal pathogen of common bean (Phaseolus vulgaris L.). Our objective was to identify QTL for resistance to white mold from wild and landrace accessions of common bean using two inbred backcross line (IBL) populations derived from the recurrent black bean parent ‘Tacana’. Selective phenotyping failed to detect QTL for field disease resistance but other agronomic traits less sensitive to environmental conditions or population size were detected. Four novel QTLs for white mold resistance WM3.3TW, WM7.5TL, WM9.2TW, and WM11.1TL were identified in the greenhouse straw test on linkage groups B3, B7, B9, and B11, respectively, and two previously mapped QTL were also validated on B2 and B4. QTL, SY2.1TL that accounted for 19–37% of the variation for yield under white mold pressure over 3 years, was detected on B2 in the TL population. Enhanced resistance to white mold in common bean could be achieved by combining different QTL associated with physiological resistance with yield under disease pressure.

Registration of Common Bacterial Blight Resistant Cranberry Dry Bean Germplasm Line USCR‐CBB‐20

Common bacterial blight (CBB; caused by Xanthomonas axonopodis pv. phaseoli) is a serious disease of dry and green beans (Phaseolus vulgaris L.) in warm humid climates. Crop loss up to 40% has been reported due to this disease, which is most prominent east of the continental divide in the United States. Cranberry beans are very susceptible to CBB, so our objective was to develop a cranberry dry bean with improved resistance to the disease. A combination of marker‐assisted selection for quantitative trait loci (QTL) for resistance in early generations followed by selection under disease pressure in later generations was used to develop the cranberry dry bean germplasm line USCR‐CBB‐20 (Reg. No. GP‐281, PI 659069), which has improved resistance to CBB. USCR‐CBB‐20, released in 2008 by the USDA‐ARS in cooperation with the Idaho and Michigan agricultural experiment stations, possesses the sequence‐characterized amplified region markers SU91 and SAP6, which are associated with CBB resistance QTL on linkage groups 8 and 10, respectively. USCR‐CBB‐20 had an average disease score of 5.3 in greenhouse tests, which is a remarkable improvement over the previous cranberry line released with CBB resistance, which scored 8.4 (9 = completely susceptible) in the same tests. Except for relatively small seed size, USCR‐CBB‐20 exhibits commercially acceptable agronomic traits for the cranberry bean market class. Yield potential was above average in Michigan and below average in Washington. USCR‐CBB‐20 will be useful for improving CBB resistance in the cranberry and other large‐seeded dry and green‐bean market classes of Andean origin.

Microsatellite Marker Characterization of Chilean Common Bean (Phaseolus vulgaris L.) Germplasm

ABSTRACTThe Chilean national common bean germplasm collection consists of 1200 accessions, most of which have not been characterized or used in breeding programs. As part of the characterization of this germplasm we have formed a core collection of 246 accessions that represent 21% of the whole collection and that consists of many race Chile representatives as well as varieties from other races that are traditionally grown in the country. The specific objectives of this work were to use microsatellites to evaluate the level of polymorphism in the Chilean core collection and to determine the genetic variability of race Chile and its relationships with other races. The results indicate that the level of polymorphism detected with microsatellites was higher than that obtained with previous molecular or biochemical markers. The number of microsatellite alleles varied from 2 to 14 and the polymorphism information content (PIC) values were 0.08 to 0.84. Heterozygosity ranged from 0 to 0.052 for each of the markers. Euclidean genetic distance ranged from 0.12% between race Chile and race Nueva Granada to 0.71% between race Chile and race Mesoamerica. Multiple correspondence analysis (MCA) showed clustering of the accessions into the two main genepools, with race Chile genotypes grouping mainly with race Nueva Granada genotypes.