Browsing by Author "Agyare, R.Y."
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Item Genetic diversity and population structure analysis of Ghanaian and exotic cassava accessions using simple sequence repeat (SSR) markers(Heliyon, 2020-01-31) Asante, I.K.; Adjebeng-Danquah, J.; Manu-Aduening, J.; Agyare, R.Y.; Gracen, V.; Offei, S.K.Genetic diversity is fundamentally important in crop improvement and provides plants with the capacity to meet the demands of changing environments. This work was carried out to assess the diversity and the extent of genetic relatedness among a number of assembled cassava (Manihot esculenta Crantz) accessions. We conducted a microsatellite marker analysis of 89 cassava accessions collected from Ghanaian and exotic sources. These accessions were assayed using 35 simple sequence repeat (SSR) markers. A total of 167 alleles were detected from 35 polymorphic markers with an average of 4.77 alleles per locus. High allelic frequency was detected across the accessions, ranging from 0.32 to 0.99 with an average of 0.62 per marker. Observed heterozygosity ranged from 0.03 - 0.97 across the accessions. Polymorphism information content (PIC) ranged from 0.03 to 0.78 with a mean of 0.45, indicating high level of polymorphism across the accessions. Comparatively, higher number of alleles, gene diversity and observed heterozygosity were detected among the local accessions compared with the exotic accessions indicating rich genetic diversity among them. Population structure analysis based on STRUCTURE identified two subpopulations and a large number of admixtures. Cluster analysis based on the neighbour joining algorithim further separated the collection into seven sub-groupings irrespective of geographical origin. This indicates the possible sharing of common genomic regions occurring across the accessions. High allelic frequency differences and levels of heterozygosity were observed among the germplasm. These findings indicated significant genetic variability in the germplasm to warrant selection.Item A novel aphid resistance locus in cowpea identified by combining SSR and SNP markers(Plant Breeding, 2018-04) Kusi, F.; Padi, F.K.; Obeng-Ofori, D.; Asante, S.K.; Agyare, R.Y.; Sugri, I.; Timko, M.P.; Koebner, R.; Huynh, B.L.; Santos, J.R.P.; Close, T.J.; Roberts, P.A.The utility of combining simple sequence repeat (SSR) and single nucleotide polymorphism (SNP) marker genotyping was determined for genetically mapping a novel aphid (Aphis craccivora) resistance locus in cowpea breeding line SARC 1‐57‐2 and for introgressing the resistance into elite cultivars by marker‐assisted backcrossing (MABC). The locus was tagged with codominant SSR marker CP 171F/172R with a recombination fraction of 5.91% in an F2 population from ‘Apagbaala’ x SARC 1‐57‐2. A SNP‐genotyped biparental recombinant inbred line population was genotyped for CP 171F/172R, which was mapped to position 11.5 cM on linkage group (LG) 10 (physical position 30.514 Mb on chromosome Vu10). Using CP 171F/172R for foreground selection and a KASP‐SNP‐based marker panel for background selection in MABC, the resistance from SARC 1‐57‐2 was introduced into elite susceptible cultivar ‘Zaayura’. Five BC4F3 lines of improved ‘Zaayura’ that were isogenic except for the resistance locus region had phenotypes similar to SARC 1‐57‐2. This study identified a novel aphid resistance locus and demonstrated the effectiveness of integrating SSR and SNP markers for trait mapping and marker‐assisted breeding.