Diversity and Pathogenicity of Fungi Associated with Dieback and Trunk Cankers in Pecan Orchards of Sonora, Mexico

Pecan (Carya illinoensis) is a major economic crop in Mexico. The states of Chihuahua and Sonora contribute approximately 80% to the national production. Recently, symptoms of trunk diseases, including necrotic lesions in the xylem, cankers, dieback, and shoot blights, have been observed in pecan orchards in Sonora. This study aimed to determine the presence and identity of fungi responsible for these symptoms. A survey was conducted between 2021 and 2022 in eleven orchards near Hermosillo, Sonora. Fungi were isolated from necrotic tissue on PDA medium, yielding around 150 isolates. Based on colony morphology, 50 isolates were selected for molecular characterization using the translation elongation factor 1 alpha (tef1-α) gene, the nuclear ribosomal DNA-internal transcribed spacer (ITS), and, for some isolates, the β-tubulin gene. The fungi identified included <i>Pseudofusicoccum stromaticum</i>, <i>Lasiodiplodia exigua</i>, <i>L. brasiliensis</i>, <i>Diaporthe caatingaensis</i>, <i>Eutypellla microtheca</i>, and several <i>Fusarium</i> spp. The optimal growth temperature for most isolates was 30°C, with none exhibited growth at 40°C, although some <i>Lasiodiplodia</i> and <i>Pseudofusicoccum</i> isolates showed limited growth at 37°C. Following pathogenicity studies, the <i>Lasiodiplodia</i> species produced the largest lesions on pecan cv. Wichita, followed by <i>P. stromaticum</i>, while <i>D. caatingaensis</i> and <i>E. microtheca</i> exhibited intermediate virulence. The least virulent were <i>D. caatingaensis</i> and <i>Fusarium</i> spp. isolates. This study contributes to understanding the phytosanitary status of pecan orchards in Mexico and lays the groundwork for developing management strategies to control these fungi.