Validation of sorghum quality control (QC) markers across African breeding lines.

Sorghum [Sorghum bicolor (L.) Moench] is a cereal crop of critical importance in the semi-arid tropics, particularly in Africa where it is second only to maize (Zea mays L.) by area of cultivation. The International Crops Research Institute for the Semi-Arid Tropics sorghum breeding program for Eastern and Southern Africa is the largest in the region and develops improved varieties for target agro-ecologies. Varietal purity and correct confirmation of new crosses are essential for the integrity and efficiency of a breeding program. We used 49 quality control (QC) kompetitive allele-specific PCR single nucleotide polymorphism (SNP) markers to genotype 716 breeding lines. Note that 46 SNPs were polymorphic with the top 10 most informative revealing polymorphism information content (PIC), minor allele frequency (MAF), and observed heterozygosity (Ho) of 0.37, 0.43, and 0.02, respectively, and explaining 45% of genetic variance within the first two principal components (PC). Thirty-nine markers were highly informative across 16 Burkina Faso breeding lines, out of which the top 10 revealed average PIC, MAF, and Ho of 0.36, 0.39, and 0.05, respectively. Discriminant analysis of principal components done using top 30 markers separated the breeding lines into five major clusters, three of which were distinct. Six of the top 10 most informative markers successfully confirmed hybridization of crosses between genotypes IESV240, KARIMTAMA1, F6YQ212, and FRAMIDA. A set of 10, 20, and 30 most informative markers are recommended for routine QC applications. Future effort should focus on the deployment of these markers in breeding programs for enhanced genetic gain.

Compilation of an informative microsatellite set for genetic characterisation of East African finger millet (Eleusine coracana)

Background Genetic diversity of finger millet (Eleusine coracana), a nutritious neglected staple cereal in Africa and South Asia is largely uncharacterized. This study analysed 82 published SSR markers for finger millet across 10 diverse accessions to compile an informative set for genetic characterisation. Extensive optimization compared single samples with bulked leaf or bulked DNA samples for capturing within accession genetic diversity. The markers were evaluated to determine (1) how efficiently they amplified target loci during high-throughput genotyping with a generic PCR protocol, (2) ease of scoring PCR products and (3) polymorphism and ability to discern genetic diversity within the tested finger millet germplasm. Results Across 88 samples, the 52 markers that worked well amplified 274 alleles, ranging from 2 to 14 per locus with a mean of 4.89. Major allele frequency ranged from 0.18 to 0.93 with a mean of 0.57. Polymorphic Information Content (PIC) ranged from 0.13 to 0.88 with a mean of 0.5 and availability varied between 64 and 100% with a mean of 92.8%. Heterozygosity ranged from 0 to 1.0, with a mean of 0.26. Discussion Five individual samples from an accession captured the largest number of alleles per locus compared to the four different bulked sampling strategies but this difference was not significant. The identified set comprised 20 markers: UGEP24, UGEP53, UGEP84, UGEP27, UGEP98, UGEP95, UGEP64, UGEP33, UGEP67, UGEP106, UGEP110, UGEP57, UGEP96, UGEP66, UGEP46, UGEP79, UGEP20, UGEP12, UGEP73 and UGEP5 and was since used to assess East African finger millet genetic diversity in two separate studies.