Pseudoplagiostoma perseae sp. nov. causes leaf spot disease on avocado leaves in Taiwan

Leaf spot disease is commonly found on leaves of avocado plants in avocado orchards in Taiwan. Needle-like spots with yellow halos appear on diseased avocado leaves at the incipient stage, and these spots gradually enlarge and become brown lesions with black-brown centers. The causal agent of this disease is unknown. A Pseudoplagiostoma species was isolated from these leaf spots. Evaluation of morphological traits and phylogenetic analysis using the ribosomal DNA internal transcribed spacer operon, β-tubulin, and partial large subunit of ribosomal DNA markers identified this fungal species as a novel species, Pseudoplagiostoma perseae sp. nov. A pathogenicity test was conducted on three avocado cultivars, ‘Choquette’, ‘Hall’, and ‘Hung Shin Yuan’. After 2 weeks of inoculation, needle-like leaf spots appeared on all three cultivars, and P. perseae was re-isolated from the spots of all inoculated leaves, fulfilling Koch’s postulates. This is the first report describing the novel species P. perseae, which was validated as the causal agent of avocado leaf spot disease.