In-depth genome characterization of a Brazilian common bean core collection using DArTseq high-density SNP genotyping.

BACKGROUND: Common bean is a legume of social and nutritional importance as a food crop, cultivated worldwide especially in developing countries, accounting for an important source of income for small farmers. The availability of the complete sequences of the two common bean genomes has dramatically accelerated and has enabled new experimental strategies to be applied for genetic research. DArTseq has been widely used as a method of SNP genotyping allowing comprehensive genome coverage with genetic applications in common bean breeding programs. RESULTS: Using this technology, 6286 SNPs (1 SNP/86.5 Kbp) were genotyped in genic (43.3%) and non-genic regions (56.7%). Genetic subdivision associated to the common bean gene pools (K = 2) and related to grain types (K = 3 and K = 5) were reported. A total of 83% and 91% of all SNPs were polymorphic within the Andean and Mesoamerican gene pools, respectively, and 26% were able to differentiate the gene pools. Genetic diversity analysis revealed an average H E of 0.442 for the whole collection, 0.102 for Andean and 0.168 for Mesoamerican gene pools (F ST = 0.747 between gene pools), 0.440 for the group of cultivars and lines, and 0.448 for the group of landrace accessions (F ST = 0.002 between cultivar/line and landrace groups). The SNP effects were predicted with predominance of impact on non-coding regions (77.8%). SNPs under selection were identified within gene pools comparing landrace and cultivar/line germplasm groups (Andean: 18; Mesoamerican: 69) and between the gene pools (59 SNPs), predominantly on chromosomes 1 and 9. The LD extension estimate corrected for population structure and relatedness (r2SV) was ~ 88 kbp, while for the Andean gene pool was ~ 395 kbp, and for the Mesoamerican was ~ 130 kbp. CONCLUSIONS: For common bean, DArTseq provides an efficient and cost-effective strategy of generating SNPs for large-scale genome-wide studies. The DArTseq resulted in an operational panel of 560 polymorphic SNPs in linkage equilibrium, providing high genome coverage. This SNP set could be used in genotyping platforms with many applications, such as population genetics, phylogeny relation between common bean varieties and support to molecular breeding approaches.

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 310 Mb 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.

Microsatellite markers for an endemic Atlantic Forest tree, Manilkara multifida (Sapotaceae).

Manilkara multifida is a tropical tree that is endemic to the Atlantic forests of southern Bahia, Brazil. Currently, populations of this species are restricted to fragmented landscapes that are susceptible to anthropogenic disturbances. Considering this issue, and that there is no genetic information available for this endangered species, we developed microsatellite markers for M. multifida to provide resources for future conservation genetics studies. Using an enriched genomic library, we isolated eight polymorphic microsatellite loci and optimized the amplification conditions for M. multifida. For each locus, we estimated the number of alleles, H E and H O, paternity exclusion Q, individual identity I and fixation index F, and examined the presence of null alleles. The mean number of alleles was 11.9, and the heterozygosity was high at all loci (average H E = 0.809 and H O = 0.777). The combined values for both paternity exclusion and individual identity were Q = 0.9959 and I = 5.45 × 10(-11), respectively. No evidence of null alleles was detected. The results of our analysis indicated that all eight microsatellites are promising for assessing questions involving inbreeding, gene flow, co-ancestry and mating patterns in M. multifida.

Microsatellite markers for Plathymenia reticulata (Leguminosae)1.

PREMISE OF THE STUDY: Microsatellite markers were developed and characterized to investigate genetic diversity and gene flow and to help in conservation efforts for the endangered timber species Plathymenia reticulata. • METHODS AND RESULTS: Eleven microsatellite loci were characterized using 60 adult trees of two populations of P. reticulata from the Atlantic Forest of southern Bahia, Brazil. Of these, nine loci were polymorphic, with an average of 4.39 alleles per locus. The average expected heterozygosity per population ranged from 0.47 to 0.55. The combined exclusion probability was 0.99996. • CONCLUSIONS: Our results reveal that the microsatellite markers developed in this study are an effective tool for paternity and genetic structure analysis that may be useful for conservation strategies.