Common Bean Accessions Research Articles

Fluorescence In Situ Hybridization (FISH)-Based Karyotyping Reveals Rapid Evolution of Centromeric and Subtelomeric Repeats in Common Bean (Phaseolus vulgaris) and Relatives.

Fluorescence in situ hybridization (FISH)-based karyotyping is a powerful cytogenetics tool to study chromosome organization, behavior, and chromosome evolution. Here, we developed a FISH-based karyotyping system using a probe mixture comprised of centromeric and subtelomeric satellite repeats, 5S rDNA, and chromosome-specific BAC clones in common bean, which enables one to unambiguously distinguish all 11 chromosome pairs. Furthermore, we applied the karyotyping system to several wild relatives and landraces of common bean from two distinct gene pools, as well as other related Phaseolus species, to investigate repeat evolution in the genus Phaseolus. Comparison of karyotype maps within common bean indicates that chromosomal distribution of the centromeric and subtelomeric satellite repeats is stable, whereas the copy number of the repeats was variable, indicating rapid amplification/reduction of the repeats in specific genomic regions. In Phaseolus species that diverged approximately 2–4 million yr ago, copy numbers of centromeric repeats were largely reduced or diverged, and chromosomal distributions have changed, suggesting rapid evolution of centromeric repeats. We also detected variation in the distribution pattern of subtelomeric repeats in Phaseolus species. The FISH-based karyotyping system revealed that satellite repeats are actively and rapidly evolving, forming genomic features unique to individual common bean accessions and Phaseolus species.

Genomic Analysis of Storage Protein Deficiency in Genetically Related Lines of Common Bean (Phaseolus vulgaris).

A series of genetically related lines of common bean (Phaseolus vulgaris L.) integrate a progressive deficiency in major storage proteins, the 7S globulin phaseolin and lectins. SARC1 integrates a lectin-like protein, arcelin-1 from a wild common bean accession. SMARC1N-PN1 is deficient in major lectins, including erythroagglutinating phytohemagglutinin (PHA-E) but not α-amylase inhibitor, and incorporates also a deficiency in phaseolin. SMARC1-PN1 is intermediate and shares the phaseolin deficiency. Sanilac is the parental background. To understand the genomic basis for variations in protein profiles previously determined by proteomics, the genotypes were submitted to short-fragment genome sequencing using an Illumina HiSeq 2000/2500 platform. Reads were aligned to reference sequences and subjected to de novo assembly. The results of the analyses identified polymorphisms responsible for the lack of specific storage proteins, as well as those associated with large differences in storage protein expression. SMARC1N-PN1 lacks the lectin genes pha-E and lec4-B17, and has the pseudogene pdlec1 in place of the functional pha-L gene. While the α-phaseolin gene appears absent, an approximately 20-fold decrease in β-phaseolin accumulation is associated with a single nucleotide polymorphism converting a G-box to an ACGT motif in the proximal promoter. Among residual lectins compensating for storage protein deficiency, mannose lectin FRIL and α-amylase inhibitor 1 genes are uniquely present in SMARC1N-PN1. An approximately 50-fold increase in α-amylase inhibitor like protein accumulation is associated with multiple polymorphisms introducing up to eight potential positive cis-regulatory elements in the proximal promoter specific to SMARC1N-PN1. An approximately 7-fold increase in accumulation of 11S globulin legumin is not associated with variation in proximal promoter sequence, suggesting that the identity of individual proteins involved in proteome rebalancing might also be determined at the translational level.

Genome-Wide Association Studies of Anthracnose and Angular Leaf Spot Resistance in Common Bean (Phaseolus vulgaris L.)

The common bean (Phaseolus vulgaris L.) is the world’s most important legume for human consumption. Anthracnose (ANT; Colletotrichum lindemuthianum) and angular leaf spot (ALS; Pseudocercospora griseola) are complex diseases that cause major yield losses in common bean. Depending on the cultivar and environmental conditions, anthracnose and angular leaf spot infections can reduce crop yield drastically. This study aimed to estimate linkage disequilibrium levels and identify quantitative resistance loci (QRL) controlling resistance to both ANT and ALS diseases of 180 accessions of common bean using genome-wide association analysis. A randomized complete block design with four replicates was performed for the ANT and ALS experiments, with four plants per genotype in each replicate. Association mapping analyses were performed for ANT and ALS using a mixed linear model approach implemented in TASSEL. A total of 17 and 11 significant statistically associations involving SSRs were detected for ANT and ALS resistance loci, respectively. Using SNPs, 21 and 17 significant statistically associations were obtained for ANT and angular ALS, respectively, providing more associations with this marker. The SSR-IAC167 and PvM95 markers, both located on chromosome Pv03, and the SNP scaffold00021_89379, were associated with both diseases. The other markers were distributed across the entire common bean genome, with chromosomes Pv03 and Pv08 showing the greatest number of loci associated with ANT resistance. The chromosome Pv04 was the most saturated one, with six markers associated with ALS resistance. The telomeric region of this chromosome showed four markers located between approximately 2.5 Mb and 4.4 Mb. Our results demonstrate the great potential of genome-wide association studies to identify QRLs related to ANT and ALS in common bean. The results indicate a quantitative and complex inheritance pattern for both diseases in common bean. Our findings will contribute to more effective screening of elite germplasm to find resistance alleles for marker-assisted selection in breeding programs.

Genetic variability of free energy in a function of drought tolerance in common bean accessions

Characterisation of bean genotypes, particularly local landraces is important for ongoing breeding programs, especially for drought tolerance. Susceptibility to drought is emphasized when bean is grown as a stubble crop and sown at the middle of summer. The aim of this study was to compare variability of ten bean genotypes to optimal (25?C) and higher (30?C) temperatures in combination with optimal (80%) and reduced (40%) field water capacity (FWC), from the point of growth (root and shoot length and fresh matter accumulation) and thermodynamic parameters of free energy (calculated parameter after drying at 60?C, 105?C and 130?C) during the early seedlings stage. Significant and positive correlation between root length and fresh matter with free energy at symplast and chemically bound water occurred under temperature stress (i.e. 30?C). Root growth and elongation were affected by drought stress, i.e. under a combination of high temperature (30?C) and water deficit (40% FWC). Based on higher energy consumption, the ability of shoot to continue a growth in stressful conditions could be possible to achieve, as was confirm through significant and positive correlation between evaluated growth parameters in shoot and free energy of free water. It could be concluded that most of the examined dry bean accessions expressed some sensitivity to stress applied. Among genotypes tested, local landrace zecak expressed lesser susceptibility to stresses applied. Accession Maksa was more tolerant to changes at cytoplasmic level, while Medijana and Sataja 425 expressed root i.e. shoot stress tolerance. Those accessions could be considered as potentially drought tolerant genotypes.

Distribution of BCMV strains in Kashmir valley and identification of resistant sources ofPhaseolus vulgaris

Extensive survey of 100 commercial bean growing areas of Kashmir was conducted during kharif 2009 and 2010 indicated only 13 locations to be free from Bean Common Mosaic Virus (BCMV) disease. The disease incidence ranged from 0.50 to 85%. The maximum disease incidence was recorded in Srinagar followed by districts Anantnag and Bandipora, respectively. Confirmation of the association of BCMV with each isolate was made by mechanical transmission, DAC-ELISA and RT-PCR. Evaluation of eighty-five accessions of common bean of diverse origin under controlled glass-house conditions identified R-40, R-155, R-3, B-6, Pencil white, SKAU-B-02, SKAU-B-01, Pointed lady, TO, P1207262, TU, KRC-5, R-14, Jubila, Contender and Monroe accessions to be resistance against all the five strains (NL-1, NL-1n, NL-7, NL-7n and NL-4) of BCMV prevalent in Kashmir.

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.

Comparisons of phaseolin type and α-amylase inhibitor in common bean (Phaseolus vulgaris L.) in China

The objective of this study was to characterize the phaseolin type and α-amylase (αAI) level in common bean (Phaseolus vulgaris L.) accessions deposited in the Chinese National Genebank. The 40 accessions sampled were common varieties originating in Asia, North America, South America, Europe, and Africa. No Inca (I-) phaseolin was observed in the accessions. Only four accessions contained Tendergreen (T-) phaseolin and the remaining 36 contained Sanilac (S-) phaseolin. αAI proteins extracted from nine accessions showed higher α-amylase inhibitory activity than the control (Phase 2, IC50=0.65μg). These common bean accessions have potential use as nutraceutical ingredients.

Landscape genetics, adaptive diversity and population structure in Phaseolus vulgaris.

Here we studied the organization of genetic variation of the common bean (Phaseolus vulgaris) in its centres of domestication. We used 131 single nucleotide polymorphisms to investigate 417 wild common bean accessions and a representative sample of 160 domesticated genotypes, including Mesoamerican and Andean genotypes, for a total of 577 accessions. By analysing the genetic spatial patterns of the wild common bean, we documented the existence of several genetic groups and the occurrence of variable degrees of diversity in Mesoamerica and the Andes. Moreover, using a landscape genetics approach, we demonstrated that both demographic processes and selection for adaptation were responsible for the observed genetic structure. We showed that the study of correlations between markers and ecological variables at a continental scale can help in identifying local adaptation genes. We also located putative areas of common bean domestication in Mesoamerica, in the Oaxaca Valley, and the Andes, in southern Bolivia-northern Argentina. These observations are of paramount importance for the conservation and exploitation of the genetic diversity preserved within this species and other plant genetic resources.

Candidate Gene Identification with SNP Marker-Based Fine Mapping of Anthracnose Resistance Gene Co-4 in Common Bean.

Anthracnose, caused by Colletotrichum lindemuthianum, is an important fungal disease of common bean (Phaseolus vulgaris). Alleles at the Co–4 locus confer resistance to a number of races of C. lindemuthianum. A population of 94 F4:5 recombinant inbred lines of a cross between resistant black bean genotype B09197 and susceptible navy bean cultivar Nautica was used to identify markers associated with resistance in bean chromosome 8 (Pv08) where Co–4 is localized. Three SCAR markers with known linkage to Co–4 and a panel of single nucleotide markers were used for genotyping. A refined physical region on Pv08 with significant association with anthracnose resistance identified by markers was used in BLAST searches with the genomic sequence of common bean accession G19833. Thirty two unique annotated candidate genes were identified that spanned a physical region of 936.46 kb. A majority of the annotated genes identified had functional similarity to leucine rich repeats/receptor like kinase domains. Three annotated genes had similarity to 1, 3-β-glucanase domains. There were sequence similarities between some of the annotated genes found in the study and the genes associated with phosphoinositide-specific phosphilipases C associated with Co-x and the COK–4 loci found in previous studies. It is possible that the Co–4 locus is structured as a group of genes with functional domains dominated by protein tyrosine kinase along with leucine rich repeats/nucleotide binding site, phosphilipases C as well as β-glucanases.

Phenotyping in the fields: dissecting the genetics of quantitative traits and digital farming.

Phenotyping in the fields: dissecting the genetics of quantitative traits and digital farming.

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.

Examination of Genetic Diversity of Common Bean from the Western Balkans

In this study, genetic diversity of 119 accessions of common bean (Phaseolus vulgaris) from five former Yugoslav republics constituting the western Balkans was assessed by 13 microsatellite markers. This set of markers has proven before to efficiently distinguish between bean genotypes and assign them to either the Andean or the Mesoamerican gene pool of origin. In this study, 118 alleles were detected or 9.1 per locus on average. Four groups (i.e., Slovene, Croatian, Bosnian, and Serbian) showed similarly high levels of genetic diversity as estimated by the number of different alleles, number of effective alleles, Shannon’s information index, and expected heterozygosity. Mildly narrower genetic diversity was identified within a group of Macedonian accessions; however, this germplasm yielded the highest number of private alleles. All five germplasms share a great portion of genetic diversity as indicated by the analysis of molecular variance (AMOVA). On the basis of the scored number of migrants, we concluded that the most intensive gene flow in the region exists in Bosnia and Herzegovina. Cluster analysis based on collected molecular data classified the accessions into two large clusters that corresponded to two gene pools of origin (i.e., Andean and Mesoamerican). We found that Andean genotypes are more prevalent than Mesoamerican in all studied countries, except Macedonia, where the two gene pools are represented evenly. This could indicate that common bean was introduced into the western Balkans mainly from the Mediterranean Basin. Bayesian cluster analysis revealed that in the area studied an additional variation exists which is related to the Andean gene pool. Different scenarios of the origin of this variation are discussed in the article.

FIELD EVALUATION AND MOLECULAR ANALYSIS OF BEAN GENOTYPES FOR RESISTANCE TO RUST DISEASE

Bean rust, caused by Uromyces appendiculatus (Pers.) Unger, is an important disease in both temperate and tropical bean production regions. Twenty two genotypes of snap bean (Phaseolus vulgaris L.) were collected and screened for resistance to bean rust disease in two seasons. Four genotypes, i.e., Concessa, Hort. 440, Coby and Hana were completely free from infection and were rated as immune to this disease. While, another four genotypes were recorded to disease severity ranged from 1.68% to 3.19% and were categorized as resistant (hypersensitive). Only one genotype was categorized as resistant with disease severity of 9.7%. The remaining 13 genotypes were susceptible having a disease severity ranged from 17.39% to 57.80%. Banding pattern of ten selected genotypes with various levels of resistance and susceptibility to bean rust and genetic diversity among them was evaluated using RAPD, ISSRs and SSRs. The three molecular systems generated total of 75 bands with polymorphism ranged from 60% to 85%. The large number of polymorphic bands allowed easy identification of the different genotypes at the DNA level. The developed dendrogram divided the common bean genotypes into two main clusters. It could be concluded that new promising resources for resistance to leaf rust were recorded in Egyptian snap bean germplasm. In addition, the developed banding patterns for these newly identified valuable Egyptian common bean accessions immune and resistant to leaf rust reported herein could support the future Egyptian snap bean germplasm collection, preservation and utilization.

An Operational SNP Panel Integrated to SSR Marker for the Assessment of Genetic Diversity and Population Structure of the Common Bean

The common bean, an important source of protein and minerals for humans, complements cereals both nutritionally and as a rotation crop, supplying nitrogen and reducing soil pathogens. The aim of this study was to develop an operational SNP-based panel for common bean in order to facilitate SSR employment in genetic diversity and population structure analyses, and its use in breeding programs. A set of 88 diverse and important common bean cultivars/lines (53), landraces (33) and wild accessions (2) were genotyped. Overall, the 58 SSRs performed better at evaluating genetic diversity (Ā = 7.38; He = 58.7 %; PI = 1.20E−45) than the 345 SNPs, of which the SSRs dinucleotides (SSR-di) were more informative (Ā = 9.92; He = 72.5 %; PI = 3.40E−26) and a selected set of 13 SSRs (Ā = 15.31/locus; He = 84.5 %; PI = 1.03E−19) allowed for the discrimination of all individuals. For the 345 high-quality scored SNPs a low combined PI (4.70E−119) and high PE (100 %) was obtained for the assessment of parentage and identity. The SNPs were very useful for linkage mapping in inter- (78.2 %) and intra-gene pool (17.7 %) crosses. Both markers afforded high resolution detection of inter-gene pool structure, with greater differentiation based on SNPs (K = 2, F ST = 0.759). The SSRs-di differentiated cultivars/lines and landraces (K = 3) of Mesoamerican origin. A set of 16 SSRs was selected to establish a routine and operational analysis of Genbank accessions allowing an efficient origin-based discrimination of common bean accessions. Operational genotyping panels based on SSRs and SNPs were derived, contributing to the growing integration of genomics with molecular breeding programs of the common bean.

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.

Determination of the population structure of common bean (Phaseolus vulgaris L.) accessions using lipoxygenase and resistance gene analog markers

The common bean (Phaseolus vulgaris L.) is an important food legume throughout the world. Because of the conservation across different plant species, it is possible to evaluate the degree of genetic diversity in the common bean using gene-based marker techniques. The lipoxygenase (LOX) and resistance gene analog (RGA) genes play an important role in the response to biotic and abiotic stresses. Eighty-six common bean accessions were genotyped using gene-based LOX and RGA markers. The total number of polymorphic bands ranged from 193 for LOX to 17 for RGA markers. We detected considerable diversity with a mean of 8.7 alleles per primer for the LOX analysis. For the RGA markers, the number of alleles per polymorphic locus varied from 1 to 4 with an average allele number of 2.8. The genetic similarity between the accessions based on the LOX and RGA markers ranged from 0.12 to 0.55. Using STRUCTURE, 3 groups were revealed among the accessions. The results of this study should provide valuable information for future studies on the genetic diversity of common bean accessions and for association mapping studies examining the relationships between the genotypic and phenotypic traits related to the stress response.

Analysis of AFLP Markers for Screening Resistance to Common Bean Roots Rot (Pythium spp.)

Aims: To investigate AFLPs for suitability as potential markers for identification of sources of Pythium resistance in bean genotypes preferred by poor small holder farmers. Place and Duration of Study: Department of biological sciences Masinde Muliro University of Science and Technology, Kenya and Bangor University, North Wales, United Kingdom, between September 2010 and December 2012. Methodology: 45 common bean accessions comprising 35 seed samples collected from farmers, market centers, as well as seed stockists and ten common bean lines generated from a conventional breeding program with differential resistance to the pathogen Pythium were subjected to AFLP analysis. Genetic characterization using cluster and principal component analysis were conducted to determine segregating patterns of bean accessions in relation to tolerant and Original Research Article Maryrose et al.; AJEA, 5(4): 374-391, 2015; Article no.AJEA.2015.039 375 susceptible bean lines. Average genetic distances were calculated and similarity coefficients subjected to unweighted pair group method of arithmetic averages to generate dendograms. Results: Two informative AFLP primer combinations yielded 194 polymorphic loci. Genetic distance of bean samples from KARI Kakamega had 56 to 414 base pairs with a variability index of 0.63 to 0.90. Combined analysis of bean accessions from KARI breeding program and market class common bean samples revealed a variability index range of 0.62 to 0.90 with 56 to 420 base pairs. PCA contributed about 51.58% on the genetic variation. Cluster analysis of the 10 KARI-Kakamega bean lines revealed that resistant bean varieties were genetically different from the susceptible bean varieties. The dendogram generated revealed four sub-groups and with the exception of Alulu, a mildly resistant cultivar, that segregated alongside resistant cultivars, resistant varieties clustered differently from susceptible cultivars. However, screening with farmers’ germplasm produced a dendogram that revealed a mixture of distinct and relatively non-distinct categorization with regard to resistance. Only resistant cultivars AN1062, R2075, R719 and R1946 and susceptible cultivars GLP2 and GLP585 clustered together as expected. The others segregated randomly alongside the farmers’ germplasm. Resistant varieties AND1062, R2075, R719, R1946 and SCAM80 were more genetically related to marketable class of beans. R1946 R719, R2075 and AND1062 are closely related genetically compared to Mw001, KK15, Alulu and GLP2. Conclusion: AFLP is a relatively informative technique that has a great potential of delineating susceptible and resistant Pythium root rot dry bean varieties, and can be used as a preliminary guide to carry out further analysis. It is notable that the AFLP markers used were not able to clearly distinguish all the cultivars comprehensively and should not be used alone in determining resistance levels. The information generated in this study will contribute to the propagation of acceptable market class bean lines with resistance to Pythium root rot for improved livelihood and increased food security.

Genetic diversity and population structure of common bean (Phaseolus vulgaris L.) accessions through retrotransposon-based interprimer binding sites (iPBSs) markers

The common bean (Phaseolus vulgaris L.) is an important crop throughout the world and is highly recommended for many developing countries due to its nutritional components. A retrotransposon-based DNA marker system, interprimer binding sites (iPBSs), developed from reverse transcriptase primer binding sites, was used to determine genetic diversity in common bean accessions. The genetic polymorphism and effectiveness of the marker system were evaluated. A total of 180 polymorphic bands were detected using 47 iPBS primers among 67 common bean accessions, with an average of 4 polymorphic fragments per primer. The genetic similarity between accessions was calculated using the software NTSYS-pc and ranged from 0.09 to 0.99. The average polymorphism information content value for the iPBS markers was 0.73. A model-based clustering method classified the common bean accessions into 4 populations using STRUCTURE software. The results indicated that the iPBS marker method can successfully determine the genetic diversity level in common bean accessions.

РЕАКЦИЯ ИНТРОДУЦИРОВАННЫХ ГЕНОТИПОВ РОДА PHASEOLUS НА ЗАРАЖЕНИЕ THIELAVIOPSIS BASICOLA (BERKELEY & BROOME) В УСЛОВИЯХ ЕСТЕСТВЕННОЙ ЭПИФИТОТИИ

A periodic phytopathology field monitoring was conducted on 35 introduced common bean (Phaseolus) accessions at Maritsa Vegetable Crops Research Institute in 2014. The epiphytotic disease black root rot on the bean crops (over 75 % reduction of the stand) was recorded for the first time for the area of Bulgaria. The causal agent isolated from the plant tissue was identified as the fungus Thielaviopsis basicola (Berkeley) Ferraris. A strong relationship between disease severity variation and environmental and soil conditions was established. Black root rot was most severe when cool and wet weather occurred from seedling time to about three weeks after planting, combined with increased soil compaction. Field resistance was recorded in Bulgarian var. “Plovdivski zult”, var. “Starozagorski tzer” and line № 564 (3,66%, 5.33% and 6,50 % dumping-off of bean seedlings, respectively). Bean accession introduced from dry climate areas were highly susceptible to black root rot pathogen (over 76.0 % dumping-off of bean seedlings). Indirect relationship was found between bean tolerance to Th. basicola and presence of the anthocyanin in the hypocotyl and seed coat color. Install the average negative correlation between seed color signs (and hypocotyl) and the resistance of plants to Th. basicola. Samples with resistance to black root rot belong to the group with beige, red, brown or black color of seeds. The presence of phenolic compounds (anthocyanins) in the seed coat and hypocotyls beans can serve as an indirect indication of the selection of resistant to black rot breeding materials.