Solanum Crops with a Focus on the African Eggplant: The Potential of Biostimulants to Enhance Stress Tolerance

Drought, salinity, and increased temperatures are a threat to food security and farmers’ income, especially in Africa where around 50% of the population is involved in agriculture. These stresses, often present together in field conditions, damage crops and can reduce yields to a highly detrimental level. To tackle this issue and ensure the availability and affordability of nutritious fresh food, tolerant varieties need to be introduced in production systems. Indigenous vegetables, often overlooked and rarely researched, offer great genetic diversity and tolerance to various stress. The African eggplant, Solanum aethiopicum, is indigenous to Africa, highly nutritious, and is present in a wide range of forms, highlighting a great genetic pool. It has the potential to enhance the resilience of agricultural land and ensure food security but is under-researched. This reviews aims at understanding the state-of-the-art research on S. aethiopicum and the effects of abiotic stress on related crops. The first part introduces the African eggplant taxonomy, cultivation, and distribution to understand the current status of this crop in Africa. Then, the effects of drought, salinity, and heat on the Solanum genus are reviewed to understand the focus of the current research and up-to-date information on S. aethiopicum studies. The effects of biostimulants to enhance stress tolerance are also discussed for each stress and their combination.