PhD Studentship : Identifying Agro-Food Industry By-Products and Agroecological Applications Stimulating Soil Microbiome Control of the Parasitic Weed Striga

Project Description:

The project focuses on the control of the parasitic weed Striga (S. hermonthica and S. asiatica) in sorghum, millet and rice crops in Senegal, Tanzania and Ethiopia. Both Strigahermonthica and S. asiatica are widely distributed parasitic weeds that infest 12-38% of the area under cereal production in Africa. Striga causes substantial yield losses in smallholder farming systems, leading to field abandonment and food insecurity⁠. For the three crops combined (sorghum, millet, rice), the estimated annual production losses amount to 6,213,000 tons of grain, worth USD 2.32 billion annually.

Decades of research on Striga have not resulted in widespread implementation of effective control strategies by smallholder farmers. Failure in identifying suitable control strategies is partly due to the multifaceted requirements for a successful striga control on smallholder farms. Technologies not only need to be effective in controlling striga in the immediate and long term, but must also be affordable, locally available, feasible in their implementation and compatible with other cropping and farming systems management practices and contexts.

The project aims to explore the effectiveness of Striga control strategies based on applications that are locally available, underutilised and therefore cheap, and/or have multiple additional benefits to crops and soils. The project will consider Striga control by (1) organic by-products or rest-stream materials from local agro-food industries or (2) locally available wild or cultivated plants, either when grown as companion crop or applied (in fresh/dried pure biomass or processed form) as soil amendment.

Soil-microbiome organisms (bacteria and fungi) were previously identified as reducing Striga seed viability or stimulating germination. Specific microbial volatile organic compounds (mVOCs) have been found to inhibit germination or to kill seeds of Striga. Management options that could foster the functional microbiome or trigger the biosynthesis of potent mVOCs, will be assessed in semi-controlled (greenhouse) and arable field settings. Organic substrates derived from local agro-food industry waste streams, or agroecological drivers (plant-based soil amendments, companion crop species) are the focal management options of this project.

The research will follow five main steps:

(1) list potential companion crops and sources of plant or animal origin through a literature search and expert consultations.

(2) narrow down to a short list of substrates and crops based on local availability, preferences and estimated costs/feasibility through discussions with local partners and scoping visits in African partner countries.

(3) analyse in the lab the chemical and biochemical contents of substrate and plant samples from the African project countries, with a specific focus on sulphur and amino acid composition and concentration.

(4) test organic substrates and companion crops in bioassays in the greenhouse at the Medway campus on sorghum/millet/rice plants growing in Striga-infested soils and measure mVOCs.

(5) field test a selection of high-potential and locally available applications in one of the African partner countries.

The PhD candidate will be part of an international team working on a 2nd phase research project (Promoting Root Microbes for Integrated Striga Eradication -PROMISE ), funded by the Bill & Melinda Gates Foundation.