German-Ethiopian SDG Graduate School CLIFOOD – Subproject: Control of the weed Striga hermonthica by the fungal biocontrol agent Fusarium oxysporum f.sp. strigae

Cereals constitute a major staple in Sub-Saharan Africa (SSA), especially maize and sorghum. The total global sorghum production in 2016 was over 63.9 million tons, and Africa produced about 29.8 million tons (47% of world’s production), whereby SSA alone accounted for about 29 million tons. In the entire SSA region, over 20 million hectares of sorghum fields are infested with the noxious hemiparasite Striga hermonthica (Delile) Benth. leading to yield loss estimated at 9.3 million tons. High temperatures and poor soil fertility (especially low N and P) favors S. hermonthica development, hence its spread is feared to be accelerated with the rising effects of climate change and soil degradation. Several control strategies have been attempted in controlling S. hermonthica, nevertheless the fungal biocontrol agent Fusarium oxysporum f.sp. strigae (Fos) has shown to be a promising and ecologically friendly bioherbicide that can effectively suppress S. hermonthica. In Western Africa, the Fos isolate “Foxy-2” has been largely successful in controlling S. hermonthica, while in Kenya (Eastern Africa) a different Fos isolate (i.e. FK3) was rather effective. This disparity in Fos effectiveness has been ascribed to isolate’s specificity/mode of action, genotype differences and location effect i.e. climatic and ecological variations involving rhizosphere microbiota and soil physicochemistry. Hence, this project aims to investigate the susceptibility pattern of different populations of S. hermonthica from SSA to Foxy-2 and FK3. This is targeted at understanding if the efficacy of Fos against S. hermonthica is explained by genetic variations rather than by ecological origin of S. hermonthica. Furthermore, the combined treatment effect of F. oxysporum f.sp. strigae with plant growth promoting rhizobacteria for better efficiency in simultaneously improving sorghum development but arresting S. hermonthica shall be investigated. The project shall apply multi-scientific approaches ranging from metabolomics, genotyping with microsatellite markers, linkage disequilibrium mapping and reporter gene technology among others, through climatic chamber, greenhouse and laboratory studies (molecular biology and microbiology) in elucidating the variable susceptibility pattern of S. hermonthica populations from SSA to Fos biocontrol agent.

This subproject is part of the CLIFOOD project which is part of the Food Security Center.