Biodiversity and relationships of Urochloa grasses for application in sustainable tropical forage systems

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More than half of the world's agricultural land is grazing land, but tropical fodder plants receive little attention. Their relationships and biodiversity are poorly understood. The Urochloa (Brachiaria) group of African grasses were brought to South America as forages and the now domesticated forage crops are important for sustainable animal production by smallholders. Within this well-demarcated PhD project we can answer critical questions about the relationships of wild African Urochloa species to the cultivated diploids and polyploids, the processes of domestication, their biodiversity, germplasm resources (in forage crops and their wild relatives), and the occurrence of genetic bottlenecks during speciation. Previous work has shown that Urochloa brizantha, U. decumbens, U. ruziziensis and U. humidicola form a complex polyploid series of uncertain origins. Work within a Global Challenges Research Fund (GCRF NERC/BBSRC) project (involving the three supervisory team members) has shown genome constitutions of polyploids, but we need to expand our work to unstudied related wild species, and define which species have provided donor diploid genomes. No phylogenetic reconstruction of Urochloa has been attempted, and the work will build a framework based on DNA and morphology, integrated with geographical, ecological and environmental data, allowing exploitation of genetic resources in breeding for sustainability now and under conditions of climate change, land-use pressures and biodiversity loss. Over the last 200 years grass taxonomists at Kew have built the classification system for African grasses, and the Kew herbarium is the only comprehensive reference collection. This project will place these species in an evolutionary context, build a bridge between plant diversity research and crop science, and contribute towards developing better forage crops for sustainable agriculture. It will exploit genetic marker systems and genome-specific sequences developed at the University of Leicester, along with germplasm collections. The results will lead to measurement of biodiversity and genome compositions in the accessions, as well as defining phylogeny and taxonomic boundaries of the Urochloa species.