Diversification and Population Structure in Common Beans (Phaseolus vulgaris L.)

Abstract

Wild accessions of crops and landraces are valuable genetic resources for plant breeding and for conserving alleles and gene combinations in planta. The primary genepool of cultivated common beans includes wild accessions of Phaseolus vulgaris. These are of the same species as the domesticates and therefore are easily crossable with cultivated accessions. Molecular marker assessment of wild beans and landraces is important for the proper utilization and conservation of these important genetic resources. The goal of this research was to evaluate a collection of wild beans with fluorescent microsatellite or simple sequence repeat markers and to determine the population structure in combination with cultivated beans of all known races. Marker diversity in terms of average number of alleles per marker was high (13) for the combination of 36 markers and 104 wild genotypes that was similar to the average of 14 alleles per marker found for the 606 cultivated genotypes. Diversity in wild beans appears to be somewhat higher than in cultivated beans on a per genotype basis. Five populations or genepools were identified in structure analysis of the wild beans corresponding to segments of the geographical range, including Mesoamerican (Mexican), Guatemalan, Colombian, Ecuadorian-northern Peruvian and Andean (Argentina, Bolivia and Southern Peru). The combined analysis of wild and cultivated accessions showed that the first and last of these genepools were related to the cultivated genepools of the same names and the penultimate was found to be distinct but not ancestral to the others. The Guatemalan genepool was very novel and perhaps related to cultivars of race Guatemala, while the Colombian population was also distinct. Results suggest geographic isolation, founder effects or natural selection could have created the different semi-discrete populations of wild beans and that multiple domestications and introgression were involved in creating the diversity of cultivated beans.

Legume Crops Phylogeny and Genetic Diversity for Science and Breeding

“…Scarlet runner bean and tepary bean accessions have been used to obtain resistance genes and other traits for common bean. Wild relatives of common bean from the same species are an important source of diversity for the crop as well (Blair et al, 2012b;Blair and Izquierdo, 2012). Tepary beans are by far the least consumed of the five cultivars, although tepary beans are still grown in northern Mexico and among native peoples in the Southwestern US.…”

“…Perhaps because of their evolution outside the wetter regions where bacterial and fungal pathogens occur, tepary beans also provide high levels of resistance to specific Xanthomonas and rust infections, respectively. Recently, Cortés et al (2012aCortés et al ( , 2012bCortés et al ( and 2013 analyzed the drought tolerance of wild common beans based on climatic data for each accession's collection site and found a correlation with allelic diversity in candidate genes for drought tolerance, such as the ASR and DREB transcription factors.…”

“…The missing ingredients for rapid advances in breeding of common bean are i) the lack of genomic or transcriptomic sequences for the other cultigens within the genus, such as lima bean, scarlet runner bean and tepary bean; ii) the small number of accessions of wild germplasm collected for each of the cultivated species and their fast disappearance in regions of heavy urbanization across the mid-elevation valleys of Latin America; and iii) the small number of inter-specific and even inter-varietal crosses that have been made for each of the cultivated groups (Blair et al, 2012a(Blair et al, , 2012b. Phenotyping, while challenging to carry out on a large scale, is quite advanced in common bean; therefore, common bean is not subject to the tremendous limitation predicted for other legume species.…”

Diversity of common bean in Jammu and Kashmir, India: a DIVAgeographic information system and cluster analysis

“…In a latest and interesting study on 27 common bean accessions, analyzed using thirteen morphological traits, the Andean accessions were found to be less diverse than the Mesoamerican accessions (Hegay et al, 2014). Both the gene pools followed parallel pathways of dissemination through the world, generating new secondary centers of diversity in Africa and Asia (Blair et al, 2012). It was not until the 15 th -16 th century that dry beans crossed the Atlantic Ocean.…”

Local Scale Genetic Diversity and its Role in Coping with Changing Climate

“…Microsatellites loci (also called single sequence repeats or SSRs, which are regions of repetitive DNA that vary in the number of repeated DNA motifs) are commonly used to assess population structure [64], as shown in Section 2.2, and may help to estimate relatedness [65], as shown in Section 3.1, due to their high polymorphism [63,66]. The PCR (polymerase-chainreaction, a procedure used in molecular biology to replicate DNA exponentially) reactions are usually multiplexed into several PCR runs.…”