Breeding for resistance to bacterial wilt in Solanaceae crops: lessons learned and ways forward for Gboma eggplant (Solanum macrocarpon L.), a traditional African vegetable

Abstract

Bacterial wilt (BW) is caused by Ralstonia solanacearum species complex (RSSC) and can lead to severe losses in a wide range of crops, including many traditional African vegetables (TAV). Given the critical role of TAV in African food security, investigations of BW incidence, distribution, and effective breeding strategies are needed to support public and private TAV breeding programs. In this review, we address key questions related to the diversity of BW pathogens, susceptible TAV hosts, distribution, incidence, breeding strategies, sources of resistance, and gaps in the development of resistant TAV varieties in Africa. We also discuss the potential of multiomics integration to enhance our understanding of the host plant defense system against BW in Solanaceae crops. We curated BW strain databases obtained from several online platforms, representing a total of 948 BW strains. Using a refined database, we highlighted the diversity of RSSC and TAV crops affected by RSSC in different regions of Africa. Out of 29 species documented to be affected by BW in Africa, ten are TAV, including widely consumed TAV such as Amaranths and nightshades. In addition, phylotypes I and III are reported to affect TAV, and the incidence can reach up to 72.4% in farmers’ fields. An overview of the first reports revealed that the disease has become a serious threat to TAV in the past decade. Finally, this review proposes a schematic map of possible avenues for successful breeding of BW-resistant TAV using Gboma eggplant as a case study.