Resistance Screening and Targeted Metabolomics Identify Potential Biomarkers for Resistance in African Eggplant Against Fusarium elaeidis Wilt

Fusarium wilt caused by Fusarium elaeidis (Foe) threatens the African eggplant (AEP), so the development of resistant genotypes is needed. The study aimed to identify genotypes resistant to Foe and analyze the changes in phenylpropanoid metabolites and phytohormones that underlie the resistance. Fifty AEPs and one Solanum melongena were screened for resistance to two Foe isolates. None of the genotypes was immune to Foe; however, two wild accessions of AEP (V37 and V181) and one S. melongena (AUB) with higher levels of partial resistance were identified. Targeted metabolite analysis of two resistant (AUB and V37) and one susceptible genotype, V64, revealed temporal and genotype-dependent metabolic reprogramming in response to Foe. However, the results did not show a linear trend for decreasing or increasing the metabolites over time, but rather an up- or down-regulation at 7, 14, or 21 days post-inoculation. Upon infection, AUB significantly increased hydroxybenzoic acid, syringic acid, and methyl jasmonate, while abscisic and chlorogenic acid levels declined. Also, V37 elevated coumaric acid, ferulic acid, hydroxybenzoic acid, and methyl jasmonate, while abscisic acid decreased. In contrast, V64 showed an early decline in IAA levels, pointing to its susceptibility to Foe. Both resistant and susceptible genotypes induced salicylic acid, but its higher accumulation in V37 than in V64 further supports their contrasting responses to Foe. The results indicate that defense mechanisms in the resistant genotypes are species-specific and separate from the susceptible response in V64. These insights expand our understanding of the contribution of phenylpropanoids and phytohormones in mediating defense responses against Foe.