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POSTERS: Late Breaking II

P-640 - Pathogenicity of Botryosphaeriaceae and Diaporthe Species Associated with Branch Canker and Dieback of English Walnut (Juglans regia) in Chile

Tuesday, August 5, 2025
10:15 AM - 11:00 AM HST
Location: Exhibit Hall 3
Abstract Text:

Recently, Diplodia mutila, Dothiorella sarmentorum, Neofusicoccum nonquaesitum, N. parvum, Diaporthe australafricana, Dia. foeniculina, and Dia. patagonica were isolated and identified from English walnut (Juglans regia) trees showing branch canker and dieback in commercial orchards in the Maule Region of central Chile. However, their pathogenicity has not yet been evaluated.  Therefore, this study aimed to assess the pathogenicity of these Botryosphaeriaceae and Diaporthe species.  Under both laboratory and field conditions, mature fruits, young leaves, green shoots, and lignified twigs were wounded and inoculated using either mycelial plugs or conidial suspension of the seven fungal species. All isolates were pathogenic, causing necrotic lesions of varying severity: 12 to 31 mm on fruits, 3 to 21 mm on leaves, 10 to 90 mm on green shoots, and 13 to 62 mm on lignified twigs. Neofusicoccum parvum and D. mutila, were the most virulent, producing the largest lesions and most severe symptoms. Neofusicoccum nonquaesitum and Do. sarmentorum showed moderate virulence, while the three Diaporthe species were less virulent. This study provides the first comprehensive evaluation of the pathogenicity of Botryosphaeriaceae and Diaporthe species on English walnut in the Maule Region of Chile.