First Report of Tomato Spotted Wilt Virus Infecting Peanut and Tomato in Mali: Molecular Evidence and Pathogenicity

Abstract

Tomato spotted wilt virus (TSWV) poses a major threat to many crops worldwide, but its presence in Mali had never been confirmed. In this study, leaf samples from peanut plants exhibiting stunting, chlorosis, and concentric ring spots suspected of being infected with TSWV were collected at the Sotuba Research Station (Mali) in 2024. RT-PCR amplification, using TSWV specific primers, of a 784 bp fragment of the nucleocapsid gene was performed, and sequencing of the TIS2 isolate confirmed infection with TSWV. Phylogenetic analysis placed the Malian isolate close to Australian and Japanese strains, with a nucleotide identity of approximately 98%. HCA analysis of TIS2 reveals, across 200 amino acids, a hydrophobic periodicity every 7 to 10 residues, indicating a compact domain structured as helices or LRR motifs. Mechanical inoculation of healthy tomato plants with the purified TIS2 strain induced necrotic and chlorotic lesions, thereby satisfying Koch’s postulates. This is the first formal report of TSWV infection in peanuts and tomatoes in Mali, highlighting a new biosecurity issue for these strategic crops. Further studies are needed to assess viral diversity, vector species, and the impact of the disease in the region.