Characterization and Pathogenicity of Monilinia yunnanensis Causing Brown Rot Disease of Malus ‘Jinxiu’ in Shaanxi, China

Stone and pome fruit trees play a significant role in fruit production and consumption in China. As an economic fruit tree variety in Shaanxi Province, the cultivation area of Malus ‘Jinxiu’ has been gradually expanding. Brown rot, caused by several species of the genus Monilinia, can result in flower blight and fruit rot, leading to serious economic losses. In September 2025, brown rot symptoms were observed on Malus ‘Jinxiu’ fruits in orchards in Shaanxi Province, China. A total of 90 isolates recovered from symptomatic fruits were identified based on morphological characteristics, pathogenicity, and multi-locus sequence analyses of the internal transcribed spacer of ribosomal DNA (rDNA-ITS), β-tubulin gene (tub2), and laccase genes (lcc2). The results showed that the causal agent of Malus ‘Jinxiu’ brown rot in Shaanxi Province is Monilinia yunnanensis. Furthermore, upon artificial inoculation, M. yunnanensis isolates from both Malus ‘Jinxiu’ and ‘Fuji’ apple hosts can cross-infect and cause brown rot symptoms. At the same time, a M. yunnanensis isolate from Malus ‘Jinxiu’ showed similar virulence on five other local cultivated apple varieties. To our knowledge, this is the first report of M. yunnanensis infecting Malus ‘Jinxiu’. This study provides a basis for developing field diagnosis and integrated control measures for brown rot disease of Malus ‘Jinxiu’ in Shaanxi Province, China.