First Report of Colletotrichum siamense and C. gloeosporioides Causing Anthracnose of Citrus spp. in Mexico

Citrus anthracnose, caused by spp., is a major disease in many citrus-growing regions of the world. During the spring of 2019, symptoms of petal necrosis and necrotic lesions on fruits were detected on Mexican lime ( ), sweet orange ( ), and grapefruit ( ) trees in three commercial orchards distributed in northern Sinaloa (El Fuerte and Ahome municipalities), Mexico. -like colonies were consistently isolated on potato dextrose agar (PDA) medium from symptomatic petals and fruits, and 30 monoconidial isolates (10 per orchard) were obtained. Five isolates were selected as representative for morphological characterization, multilocus phylogenetic analysis, and pathogenicity tests. The isolates were designated as FAVF355-FAVF359 and were deposited in the Culture Collection of Phytopathogenic Fungi of the Faculty of Agronomy of El Fuerte Valley at the Autonomous University of Sinaloa (Mexico). Colonies grown on PDA at 25ºC were cottony, dense, with grayish white aerial mycelium and with pink conidial masses. Conidia ( = 100) were cylindrical, hyaline, aseptate, 13.7 to 18.8 × 4.3 to 5.8 μm, with both ends rounded. Based on morphological features, the five isolates were tentatively identified in the species complex (Weir et al. 2012). For molecular identification, total DNA was extracted, and the internal transcribed spacer (ITS) region (White et al. 1990), and partial sequences of actin (ACT), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), and β-tubulin (TUB2) genes were amplified by PCR (Weir et al. 2012), and sequenced. A phylogenetic tree based on Bayesian inference for species belonging to the species complex was constructed. The multilocus phylogenetic analysis distinguished the isolates FAVF355-FAVF357 as sensu stricto and the isolates FAVF358-FAVF359 as . The sequences were deposited in GenBank (accession numbers ITS: MT850050-MT850054; ACT: MT834528-MT834532; GAPDH: MT855979-MT855982; TUB2: MT834533-MT834536). Pathogenicity of the five isolates was verified on healthy fruits of their original host species. Five fruits per isolate were inoculated using the colonized agar plug method. Fruits were wounded with a sterile toothpick and mycelial plugs (5 mm in diameter) removed from the margin of a 6-days-old culture were placed onto three wound sites in each fruit. Non-colonized agar plugs were placed on the wounds of 10 fruits used as the control. The fruits were kept in a moist chamber at 25°C for 8 days. The experiment was repeated twice. All inoculate