Next-generation genomics-assisted characterization of genetic and phenotypic diversity in yams (Dioscorea spp) to support conservation and breeding for food security
Tessema, Gezahegn Girma
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Yams (Dioscorea spp) are staple edible tuber food crop, a favored source of medicinal plants with socio-cultural value in West Africa, Asia, Far East, Oceania and the Caribbean regions. However, the knowledge on the extent of genetic diversity and relationship between the main cultivated Dioscorea species and wild relatives, molecular tools to support conventional taxonomic identification and genes responsible for key traits are limited. In the current project first we have evaluated the performance of candidate DNA barcode regions of flowering plants for distinguishing Dioscorea species. Important markers were identified that fulfill better the criteria for good DNA barcode regions in terms of PCR amplification, sequence quality and discriminatory power. The second research question demonstrated genetic relationship, variation in ploidy level, pattern of heterozygosity and allele sharing, contribution of wild relatives to cultivated species and confirmation on the previous and new suggestions in guinea yams taxonomy utilizing next generation sequencing based genotyping, GBS (genotyping by sequncing), combined with ploidy level and morphological data. The research project also explored morphological, ploidy and genetic variation across aerial tuber and non-aerial tuber producing D. alata accessions. The different patterns in terms of ploidy level, morphological traits and genetic variation revealed across D. alata accessions generally higlighted the importance of developing cultivars with aerial tubers in yam improvement programs as a contribution to solve the challenge with yam planting materials. The fourth research question aimed to analyze transcriptomes in relation to flowering and sex differentiation using high throughput Super-SAGE (Serial Anaysis of Gene Expression) technique and discovered several candidate genes. In addition the study explored variation in flower sex type and other morphological traits across D. rotundata genebank accessions. In general this study presents novel approaches for the improvement of yams (Dioscorea spp) genetic resource conservation and breeding.
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