First Report of Causing Anthracnose on Pitahaya Fruit in Mexico.

Pitahaya ( spp.), also called dragon fruit, is a cultivated cactus that is native to Mexico as well as Central and South America. In October 2021, anthracnose symptoms were observed on fruit of pitahaya () in a commercial orchard located in Culiacán, Sinaloa, Mexico. Lesions on fruit were circular, sunken, dark brown and with halo. To fungal isolation, small pieces from adjacent tissue to lesions of symptomatic fruits were surface disinfested by immersion in a 2% sodium hypochlorite solution for 2 min, rinsed in sterile distilled water, and placed in Petri plates containing potato dextrose agar (PDA). The plates were incubated at 25 ºC for 5 days in darkness. -like colonies were consistently observed on PDA and five monoconidial isolates were obtained. An isolate was selected as a representative for morphological identification, multilocus phylogenetic analysis, and pathogenicity tests. The isolate was deposited as CCLF186 in the Culture Collection of Phytopathogenic Fungi at the Research Center for Food and Development (Culiacán, Sinaloa). On PDA, initially white colonies turned grey with abundant orange conidia masses at 8 days after incubation at 25 ºC. Conidia were cylindrical, with ends rounded, aseptate, hyaline, and measuring 15.2 to 18.9 × 4.3 to 6.4 μm (= 100). Appressoria were terminal, subglobose to clavate, of 7.4 to 11.6 × 5.9 to 8.2 µm (= 30). Setae were not observed. These morphological characters were consistent with those reported for the species complex (Weir et al. 2012). To determine the phylogenetic identity of the isolate CCLF186, genomic DNA was extracted following the CTAB method (Doyle and Doyle 1990), and the internal transcribed spacer (ITS) region, the intergenic region, as well as partial sequences of actin () and glyceraldehyde-3-phosphate dehydrogenase () genes were amplified and sequenced using the primers pairs ITS5/ITS4 (White et al. 1990), AM-F/AM-R (Silva et al. 2012), GDF/GDR, and ACT-512F/ACT-783R (Weir et al. 2012), respectively. The sequences were deposited in GenBank under accession nos. OP269659 (ITS), OP302778 (), OP302777 (), and OP302779 (). BLASTn searches revealed high identity with sequences of (CBS 124949) for ITS (100%), (100%), (100%), and (100%). A phylogenetic tree based on Bayesian inference and Maximum Likelihood methods, including published ITS, , and sequence datasets for isolates in the species complex was generated. The phylogenetic analysis based on the concatenated sequences clustered the isolate CCLF186 with the reference isolates. Pathogenicity of the isolate CCLF186 was confirmed on 10 healthy pitahaya fruits without wounds. A drop of a conidial suspension (1 × 105 spores/ml) was placed on two locations on each fruit. Ten control fruits were treated with sterilized water. The fruits were kept in a moist plastic chamber at 25°C and 12 h light/dark for 8 days. The pathogenicity test was repeated twice. All inoculated pitahaya fruits exhibited sunken and necrotic lesions 6 days after inoculation, whereas no symptoms were observed on the control fruits. The fungus was consistently re-isolated only from the diseased fruits and found to be morphologically identical to the isolate used for inoculation. Recently, causing anthracnose in dragon fruit () was reported from Philippines (Evallo et al. 2022). Now, this is the first report of causing fruit anthracnose in in Mexico and worldwide. These findings provide a basis for research about the distribution and effective disease-management strategies.