Dynamics of abscission of reproductive structures in common bean access

Genotypes from the Andean and Mesoamerican gene pool can present contrasting behavior for reproductive structures fixation. The subject of this study was to determine the dynamics associated with the abscission of reproductive structures for common bean accesses from Andean and Mesoamerican gene pools in protected cultivation conditions. The experiment was carried out in a greenhouse, using seven common bean accesses from Embrapa Arroz e Feijão and the experimental design consisted of a randomized complete block design. The evaluations made were based on the number of days to begin flowering, flowering period, number of emitted flowers per plant, number of flower buds, flowers and pods aborted per plant, total number of pods per plant and number of seeds per plant.Certain characteristics were considered to be highly significant, such as the amount of days to begin flowering, the flowering period, percentage of aborted pods and number of harvested pods. The Mesoamerican accesses that presented greater abortion also produced more flowers, which suggests that abortion of reproductive structures can be a natural adjustment of the plant. Andean accessions with shorter reproductive period showed greater pod abortion. The dynamics of flower and pod abscission in the common bean proved to be widely variable depending on the different gene pools and genotypes evaluated and due to growth habit.

Population structure, genetic diversity and genomic selection signatures among a Brazilian common bean germplasm

Brazil is the world's largest producer of common bean. Knowledge of the genetic diversity and relatedness of accessions adapted to Brazilian conditions is of great importance for the conservation of germplasm and for directing breeding programs aimed at the development of new cultivars. In this context, the objective of this study was to analyze the genetic diversity, population structure, and linkage disequilibrium (LD) of a diversity panel consisting of 219 common bean accessions, most of which belonging to the Mesoamerican gene pool. Genotyping by sequencing (GBS) of these accessions allowed the identification of 49,817 SNPs with minor allele frequency > 0.05. Of these, 17,149 and 12,876 were exclusive to the Mesoamerican and Andean pools, respectively, and 11,805 SNPs could differentiate the two gene pools. Further the separation according to the gene pool, bayesian analysis of the population structure showed a subdivision of the Mesoamerican accessions based on the origin and color of the seed tegument. LD analysis revealed the occurrence of long linkage blocks and low LD decay with physical distance between SNPs (LD half decay in 249 kb, corrected for population structure and relatedness). The GBS technique could effectively characterize the Brazilian common bean germplasms, and the diversity panel used in this study may be of great use in future genome-wide association studies.

Genetic variation in common bean (Phaseolus vulgaris L.) using seed protein markers

The genetic diversity of common bean accessions were assessed using seed storage protein markers. At regional level, accessions from the two major growing regions showed the highest level of gene diversity (H = 0.322, I = 0.485, and H = 0.312, I = 0.473), which can be exploited for the future improvement of the crop. Based on phaseolin, the major storage protein in common bean, the majority of the accessions (86%) were grouped under Mesoamerican gene pool. Seed proteins were also used to differentiate various Phaseolus species, indicating the usefulness of seed storage proteins in species identification in this genus.

Genetic variation, Heritability estimates and GXE effects on yield traits of Mesoamerican common bean (Phaseolus vulgaris L) germplasm in Uganda

Germplasm of common beans from the Mesoamerican gene pool races: Durango, Jalisco, Mesoamerica and Guatemala have highest genetic variation for the crop's improvement. The objective was to assign 50 common bean germplasm in Uganda into its gene pool races based on analyses of population structure. Secondly, to estimate heritability and effects of genotype × environment (GXE) interaction on common bean agronomic and yield traits in space and time. Sample genomic DNA was amplified in 2011 with 22 Simple sequence repeat markers (SSRs) and alleles separated using capillary electrophoresis. Field evaluations were conducted in 2010 and 2011 at NaCRRI and 2015 at CIAT – Kawanda. Multivariate analyses of SSRs data identified four subgroups within the germplasm: K4.1–K4.4, with corresponding Wrights fixation indices (FST) as 0.1829 for K4.1, 0.1585 for K4.4, 0.1579 for K4.2 and least for K4.3 at 0.0678. Gene pool race admixtures in the population (14%) were notable and attributed to gene flow. Four superior parents currently used in improving resistance to major diseases grouped as; Jalisco for MLB49-89A; Mesoamerica for MCM5001 and G2333; Durango for MEXICO 54. Heritability values for yield traits estimated using phenotypic data from above fixed parents, was above 0.81. Season and location had significant effect (P < 0.05) on numbers of: flower buds per inflorescence, pod formation and weight of 100 seeds. The findings will improve understanding of co-evolutionary relationships between bean hosts and pathogens for better disease management and will broaden the germplasm base for improving other tropical production constraints.

Variability of nodulation traits in Andean and Mesoamerican common bean gene pools

The objective of this work was to evaluate the genotypic diversity for nodulation in common bean (Phaseolus vulgaris) genotypes of Andean and Mesoamerican gene pools present in the core collections of Embrapa, in Brazil. Evaluations were carried out in two stages: the first one with 879 genotypes, taking the cultivar 'Ouro Negro' as reference; and the second one with 116 genotypes with greater nodulation, to identify those showing stability in nodulation in the two stages. Rhizobium strains were inoculated in pre-germinated common bean seed. Plants received weekly a nutrient solution without N, and nodulation was evaluated 35 days after planting. The percentage of genotypes that exceeded the reference cultivar was 22% for number of nodules, 46% for nodule dry weight, and 33% for one nodule dry weight. The combined analysis of data from the two evaluation phases showed wide differences among genotypes, and significant interactions between genotypes and stages. By the orthogonal contrasts analysis, the Mesoamerican genotypes showed a greater nodulation than the Andean ones. In both stages, twenty-six more stable genotypes were identified, most of them belonging to the Mesoamerican gene pool. There is a large variability in nodulation traits among the common bean genotypes present in the core germplasm collections of Embrapa, which suggests that there are genotypes with improved nodulation.

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.

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.

Genetic control of iron concentration in Mesoamerican and Andean common bean seeds

The objective of this work was to evaluate the main differences in the genetic control of the iron concentration in Mesoamerican and Andean common bean seeds, in early generations, and to select recombinants with a high iron concentration in the seeds. F1, F1 reciprocal, F2, F2 reciprocal, and backcross (BC11 and BC12) generations were produced by crosses between Mesoamerican (CNFP 10104 x CHC 01-175) and Andean (Cal 96 x Hooter) inbred lines. The expression of significant maternal effect was observed for the Mesoamerican gene pool. Iron concentration was higher in the seed coat of Mesoamerican common bean seeds (54.61 to 67.92%) and in the embryo of Andean common bean seeds (69.40 to 73.44%). High broad-sense heritability was obtained for iron concentration in Mesoamerican and Andean common bean seeds. Gains with the selection of higher magnitude, from 20.39 to 24.58%, are expected in Mesoamerican common bean seeds. Iron concentration in common bean seeds showed a continuous distribution in F2, which is characteristic of quantitative inheritance in Mesoamerican and Andean common bean seeds. Recombinants with high iron concentration in seeds can be selected in both Mesoamerican and Andean common bean hybrids.

Identification of the variability of a common bean collection through morphological, physiological, biochemical, and molecular relationships

The present study was carried out in Corpoica, C.I. Tibaitata (Mosquera, Colombia) at an altitude of 2,540 m a.s.l. in six environments composed of different seasons and at an altitude of 1,485 m a.s.l. in the International Center for Tropical Agriculture (CIAT ), Calima, Colombia. Morphological, physiological, biochemical, and molecular descriptors were used to estimate the genetic variability between 36 Colombian bean accessions, of which four were wild and the others cultivated. Diacol Calima (Nueva Granada from the Andean gene pool) and ICA Pijao (Mesoamerican from the mesoamerican gene pool) were used as controls. The combined analysis of the qualitative and quantitative variables was carried out with Gower distance and an unified data matrix with 315 descriptors. The relationships between the genetic distances differentiated the bean collection into two genetic groups: Andean and Mesoamerican. The following groups of characteristics presented high association: total morphology with qualitative morphology (P=0.91), physiological evaluation with grouped evaluation of morphological, quantitative, and physiological characteristics (P=0.91), characterization of isoenzymatic and molecular markers with respect to just molecular markers (P=0.99) and the characterization of all the studied markers in relation to the molecular and isoenzymatic markers (P=0.88).