Characterization and Biological Characteristics of Alternaria, Botryosphaeria, Pestalotiopsis, and Trichothecium Species Associated with Postharvest Loquat Fruit Rot in Yunnan, China

Postharvest diseases caused by various fungal pathogens pose a significant threat to fruit quality, storage, and market value, making their identification and biological characterization essential for effective management strategies. This study examines the morphological and phylogenetic characteristics of Alternaria, Botryosphaeria, Pestalotiopsis, and Trichothecium species associated with loquat fruit rot in Yunnan, China. In May 2023, fruit rot of loquat in Yunnan, China, was classified into four types: ring rot, brown spot, black spot, and soft rot, with incidence rates of 4%, 6%, 6%, and 12%, respectively. Based on morphological features and molecular approaches, two strains of Botryosphaeria were identified as Botryosphaeria dothidea, which causes ring rot. Three strains of Trichothecium were identified as Trichothecium roseum, which is responsible for the brown spots. Three strains of Alternaria were identified as Alternaria alternata, which led to the appearance of black spots on the leaves. Similarly, two strains of Pestalotiopsis were identified as Pestalotiopsis kenyana, which causes soft rot. All identified species were verified to induce harvest loquat fruit rot by validating Koch’s postulates. This is the novel report of B. dothidea, T. roseum, and P. kenyana inducing postharvest fruit rot on loquat in Yunnan, China, and globally. It is also the first evidence that A. alternata causes postharvest fruit rot and gray leaf spot on loquat in Yunnan, China. The virulence differed among species, even within isolates of the same species. Additionally, the effect of temperature on the pathogenicity of A. alternata on loquat leaves was more than humidity. These findings enhance our understanding of the fungal pathogens affecting loquat fruit in the study area and highlight the importance of effective management strategies to minimize fruit rot. Further research is needed to investigate the ecological impacts of these species and potential control measures in agricultural practices.