Improving production efficiency of African Eggplant (Solanum aethiopicum) for smallholder farmers in sub-Saharan Africa

Malnutrition affects one in three people on the planet, with 2 billion people being deficient in one or more micronutrients. In Sub-Saharan Africa malnutrition is a chronic problem. The sustainable production and consumption of biodiverse nutritious horticultural crops provide a key part of the solution to this problem. There are many indigenous vegetable species that are grown in Africa and sold in local markets, mainly by female producers, as a source of income to alleviate their poverty. However, many of these crops are under-researched and their full potential has not been realised. African eggplant, Solanum aethiopicum, is such a crop. It is widely consumed across both West and East Africa as a leafy vegetable and also as a fruit. Solanum aethiopicum is closely related to Solanum melongena, aubergine/eggplant, and to tomato, Solanum lycopersicum and potato, Solanum tuberosum. Similar to these Solanum species, the availability of soil water and the health of the soil, as defined by the presence or absence of diseases, will greatly affect productivity and nutritive content. There is therefore an immense potential to improve the production of African eggplant through better water management strategies, improving soil health and growing varieties that are more resilient to water stress. Here we will adopt two major approaches to maximise African eggplant production: 1) developing new plant and crop management strategies to improve production; 2) characterise the genetic diversity towards identifying more drought resilient accessions of African eggplant.

To inform best practice for irrigating African eggplant we will characterise the current commercial varieties' responses to a range of soil water deficits. Under controlled conditions we will identify the range of soil matric potentials and volumetric water contents that support optimum yields and nutritive quality. We will test the potential of using hyperspectral imaging to identify the onset of plant water stress and its use as a tool to identify water resilient lines. Responses to soil water deficits will be further investigated in pot experiments in Africa prior to testing in the field. We will also determine if nursery plants can be primed for a greater resilience to soil water stress and soil health before planting in the field. This will be done by using a mild wilting stress and the use of arbuscular mycorrhiza to induce better plant performance. Our final plant management strategy is to improve soil health. First we will characterise the DNA present in the soil on African farms to gain understanding of the microbes present and thus soil health. This will inform which soil amendments will have greatest potential to improve soil health, and these will be tested on the farms. We will assess the effect of these management practices on African eggplant productivity and take into account the economic cost and farmer preference towards generating best practice guides.

At the same time as improving crop management we will characterise the extensive germplasm in our collection. To gain understanding of the potential diversity we will resequence the genomes of 20 accessions and identify the variation. We will multiply the seed in our collection and evaluate, in association with farmers, 160 accessions in drought-prone areas and characterise which lines are more resilient to low soil water availability. Based on farmer feedback we will phenotypically characterise in more detail the preferred accessions and initiate crosses of the best performing lines to advance current breeding programmes. To help inform breeding efforts, we will characterise a population of African eggplants that segregate for their ability to grow under increasing soil water deficits. We will identify molecular markers that are linked to better drought resilience that can be deployed in the breeding programmes.

We will improve African eggplant productivity by developing integrated plant management strategies and novel germplasm resources. We will identify the soil matric potentials below which plant productivity is reduced to inform new irrigation strategies. We will also test the feasibility of identifying spectral indices that can be used to monitor crop performance when under water stress. We will repeat and refine the pot-based experiments in Africa to account for higher evaporative demands before rolling out alternate wetting and drying irrigation regimes on African farms.
We will also develop a system of stress-priming seedlings in the nursery prior to field planting; this will include short-term wilting stress and the use of arbuscular mycorrhizal fungi. Successful priming treatments will be rolled out to African farmers. We will sequence the soil microbiome from three different farming regions to gain insight into soil health, as measured by the presence and absence of pathogenic microbes. We will develop and test soil amendments and quantify effects on soil health and productivity.
Simultaneously we will multiply the seed of 200+ accessions in our germplasm collections and grow out accessions on farms in drought-prone areas to select the ~40 best performing lines for more detailed phenotype analysis. This will include analysis of root and shoot characteristics under soil water deficits. We will sequence 20 accessions to gain insights into the potential diversity in our germplasm collection and to identify SNPs to aid the analysis of a mapping population segregating for responses to limiting soil water availability. We will identify markers linked to improved productivity under soil water deficits. We will initiate crosses of the most promising resilient accessions to advanced breeding lines.
Throughout these investigations, we will involve farmers and breeders to assess crop performance and review the economic potential of any new growing methods and cultivars.

Our vision is to carry out our research to directly benefit African farmers and consumers by improving human nutrition and poverty alleviation through the enhanced production of African eggplant.

From the beginning of the project until the end we will engage with farmers and breeders in Uganda and Tanzania towards delivering solutions in increasing the production of this crop.

The main beneficiaries will be male and female smallholder farmers and their dependants. They will gain from being able to help select new accessions from our collections that will enter the breeding programmes or be directly adopted. They will also gain from being shown how irrigation methods can improve productivity. Working with farmers and showing how priming nursery seedlings can improve crop performance will be an additional plant management methodology that farmers will gain. They will also directly gain experience and understanding in how soil amendments will help improve soil health and future crop performance.
Ultimately smallholders' income will improve from the increased resilient production and selling more in local markets, which will make paying for medical care and school fees easier thus improving general domestic harmony.

Breeders of African Eggplant will gain from being able to view the accessions being grown during our seed multiplication and drought resilience assessments. They will be able to select lines for crossing into their breeding programmes not only based on drought resilience but on key horticultural traits that they are targeting for improvement. Breeders will also benefit from the genome sequences, SNP data and molecular markers linked to drought resilience that we will identify. This help in speeding up their development more drought resilient lines. Similarly the development of an image based system that will indicate when reduced water level is impacting on growth and development will help breeders rapidly phenotype and select more drought resilient plants in their segregating populations. Breeders will also profit from access to any initial crosses between lines that we generate during the course of our research.

The above are direct beneficiaries of our research. There will be many indirect beneficiaries through the improved production of African Eggplant and the translation of our research to other vegetable crops. Local African communities will benefit from the enhanced availability of more nutritious local produce that will help to improve their health and well-being. In peri-urban areas where supply chains are developed retailers will benefit from consistent supply of produce. Ultimately producer organisations working in Africa exporting vegetables to Europe will also gain from a more resilient and sustainable source of vegetables.