Improving food security in Africa: taxonomy, genetics and ecology of finger-grasses

Modern African agriculture is precariously reliant on crops introduced by European settlers. These foreign and genetically uniform food and forage plants are susceptible to disease and require more water than is frequently available. They are failing to support the continent's growing population. Yet the agricultural industry has forgotten plants native to Africa: unfamiliar to food and pasture production industries yet evolved under drought, locally diverse, and with potential which is largely untapped due to the lack of a basic botanical knowledge base.

The finger-grasses (Poaceae genus Digitaria) are a significant global knowledge gap, a group of 277 grasses with superficially similar finger-like inflorescences and tiny flowering parts, with differences important for identification not visible without a powerful microscope. They are commonly missed by field surveys; there has been no attempt at a taxonomic treatment since 1950; and their evolutionary relationships are unknown. Multiple levels of polyploidy have been recorded, nuclear gene histories are complex, and finger-grasses may not even be a single evolutionary lineage. Yet across Africa Digitaria produces abundant juicy leaves loved by all cattle and Pangola grass (Digitaria eriantha) is cultivated for pasture. African Digitaria includes the mysterious fonio: world's only known crop which is a mixture of two genetically different species: Digitaria exilis and Digitaria iburua. Other species have become vigorous weeds of global importance.

This project will investigate the evolutionary history and environmental niches of Digitaria in Africa in order to propose the most optimal future forage and food exploitation for resilience against land use change associated with population increase, drought and climate change. All species of African Digitaria already known for commercial uses will be investigated genetically and experimentally to establish their distribution, abundance, phenology, and yields. Herbarium specimens at Kew will be studied to determine species boundaries through morphological taxonomy. Phylogenetic reconstructions will be made through NGS sequence data in order to identify species with best potential for feeding animals and people. Niche modelling will explore areas Digitaria can be useful under different climate change scenarios.

The student will be hosted at Royal Botanic Gardens Kew, Institut d'Economie Rurale in Mali, and Imperial College's international centre of excellence in ecology and evolution (https://www.imperial.ac.uk/visit/campuses/silwood-park), under its Grand Challenges in Ecosystems and the Environment Initiative (http://www.imperial.ac.uk/ecosystems-and-environment).