First Occurrence of Coffee (Coffea arabica L.) Wilt Disease Caused by Neocosmospora falciformis in Saudi Arabia as Corroborated by Molecular Characterization and Pathogenicity Test

Coffee wilt represents one of the most devastating diseases of Arabica coffee (Coffea arabica L.) plantations in the primary coffee-producing regions. In this study, coffee trees manifesting wilt symptoms accompanied by the defoliation and drying of the whole tree were observed in the Jazan, El Baha, Najran, and Asir regions. The purpose of this investigation was to isolate and identify the Fusarium species recovered from symptomatic coffee trees. The developed fungi were initially characterized based on their morphological features followed by molecular phylogenetic multi-locus analysis of the combined sequences of ITS, TEF1-α, RPB2, and CaM. Twenty-five isolates were recovered from 28 samples. All fungal isolates were categorized morphologically under the genus Fusarium. Phylogenetic analysis positioned all the representative 15 isolates into one cluster grouping together with Neocosmospora falciformis (formerly F. falciforme) confirming their taxonomic position. Pathogenicity tests of the N. falciformis isolates were subsequently conducted on coffee seedlings, and the results revealed that all isolates induced wilt symptoms resembling those recorded in the field, and the incidence was 100%. The fungicide sensitivity test of seven investigated fungicides revealed that Maxim XLR○ followed by MoncutR○ exhibited the highest inhibitory effect against N. falciformis KSA 24-14, reaching 93.33% and 91.67%, respectively. To our knowledge, N. falciformis is a new causal pathogen of coffee wilt in Saudi Arabia. Remarkably, these results offer important insights for devising effective approaches to monitor and control such diseases.