Multi-Locus Phylogenetic Analysis Revealed the Association of Six Colletotrichum Species with Anthracnose Disease of Coffee (Coffea arabica L.) in Saudi Arabia

Several Colletotrichum species are able to cause anthracnose disease in coffee (Coffea arabica L.) and occur in all coffee production areas worldwide. A planned investigation of coffee plantations was carried out in Southwest Saudi Arabia in October, November, and December 2022. Various patterns of symptoms were observed in all 23 surveyed coffee plantations due to unknown causal agents. Isolation from symptomatic fresh samples was performed on a PDA medium supplemented with streptomycin sulfate (300 mg L(−1)) and copper hydroxide (42.5 mg L(−1)). Twenty-seven pure isolates of Colletotrichum-like fungi were obtained using a spore suspension method. The taxonomic placements of Colletotrichum-like fungi were performed based on the sequence dataset of multi-loci of internal transcribed spacer region rDNA (ITS), chitin synthase I (CHS-1), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), actin (ACT), β-tubulin (TUB2), and partial mating type (Mat1–2) (ApMat) genes. The novel species are described in detail, including comprehensive morphological characteristics and colored illustrations. The pathogenicity of the isolated Colletotrichum species was assessed on detached coffee leaves as well as green and red fruit under laboratory conditions. The multi-locus phylogenetic analyses of the six-loci, ITS, ACT, CHS-1, TUB2, GAPDH and ApMat, revealed that 25 isolates were allocated within the C. gloeosporioides complex, while the remaining two isolates were assigned to the C. boninense complex. Six species were recognized, four of them, C. aeschynomenes, C. siamense, C. phyllanthi, and C. karstii, had been previously described. Based on molecular analyses and morphological examination comparisons, C. saudianum and C. coffeae-arabicae represent novel members within the C. gloeosporioides complex. Pathogenicity investigation confirmed that the Colletotrichum species could induce disease in coffee leaves as well as green and red fruits with variations. Based on the available literature and research, this is the first documentation for C. aeschynomenes, C. siamense, C. karstii, C. phyllanthi, C. saudianum, and C. coffeae-arabicae to cause anthracnose on coffee in Saudi Arabia.