Abstract:[Objective] We isolated and identified walnut blight pathogen from diseased walnut growing in Jiange county, Guangyuan city, Sichuan province, to control the disease. [Methods] A total of 30 infested branch samples at different developing stages were randomly collected. Pathogen isolation and purification were conducted from walnut twigs tissue by normal tissue isolation method. To fulfill Koch’s postulates, pathogenicity test was done with the isolates. In addition, the pathogen was identified based on morphological characteristics and molecular biotechnology, and biological characteristics were determined using colony growth methods. [Results] In total 180 isolates were obtained. The pathogenicity test showed that the pathogens of walnut twig blight were mainly caused by Phompsis capsici. On PDA plate, the mycelium of the pathogen was white. The spore-bearing structures could generate oval and linear conidiums. PDA medium was the most appropriate for mycelium growth. The mycelium could effectively use a variety of carbon and nitrogen sources. Among the 9 carbon and nitrogen sources tested, the appropriate carbon sources were sucrose and fructose and the optimum nitrogen sources were molybdenum acid and phenylalanine. The best mycelium growth was obtained at 25 °C and pH between 6.0 and 7.0. The mycelium grew fastest under dark conditions. [Conclusion] Phompsis capsici can easily invade from wounds to cause disease.
