Molecular Identification and Pathogenicity of Diaporthe eres and D. hongkongensis (Diaporthales, Ascomycota) Associated with Cherry Trunk Diseases in China.

ABSTRACT

This study aimed to identify fungal species associated with trunk diseases of sweet cherries (Prunus avium) in several commercial cherry orchards in Beijing, Guizhou and Shandong provinces, China. In total, eighteen fungal strains that fitted well into the species concept of Diaporthe were isolated. Based on both morphological and multi-locus phylogenetic analyses of internal transcribed spacer region (ITS), beta-tubulin (tub-2), calmodulin (Cal) and translation elongation factor 1-α (tef1-α) sequencing data, fourteen isolates were identified as Diaporthe eres, while four isolates were classified as D. hongkongensis. Here, we report D. hongkongensis causing sweet cherry branch dieback disease and, further, we confirmed the host association of D. eres with sweet cherries in China. A pathogenicity assay revealed the ability of both D. eres and D. hongkongensis to cause shoot necrosis and stem lesions on Prunus avium cv. 'Brooks' (mean lesion lengths of 1.86 cm and 1.56 cm, respectively). The optimal temperature for the growth of both Diaporthe species was tested. The optimal growth temperature for D. hongkongensis was 30 °C, and the 25-28 °C temperatures were the most favorable for the growth of D. eres strains. This research advances the understanding of fungal trunk diseases in fruit crops, particularly gummosis and branch dieback disease in Chinese cherry orchards, and will aid growers in making decisions about cultural practices and disease management.