Pseudoplagiostoma Causing Leaf Spot Disease in Key Tropical Fruit Crops in Thailand

Fruit crops have a pivotal role in Thailand's economy. Continuous evaluation of 13 potential and emerging diseases in fruit crops is important. Necrotic and discolored leaf spots were observed in Persea americana (avocado) and Mangifera indica (mango). The isolated fungi from the leaf spot were identified through multi-loci phylogenetic analyses using a concatenated matrix of ITS, LSU, tef1α, and tub2. The fungal isolates from Pe. americana were identified as Pseudoplagiostoma perseae, and isolates from Mangifera indica were identified as Ps. mangiferae. The pathogenicity assays confirmed that Ps. perseae causes leaf spots of Pe. americana, while Ps. mangiferae causes leaf blotch of M. indica. The pathogenicity of Ps. perseae and Ps. mangiferae has been reported in China and Taiwan. Hence, this study provides a report of the novel geographical distribution of Ps. perseae and Ps. mangiferae. Moreover, the cross-inoculation tests of Ps. perseae and Ps. mangiferae on M. indica and Pe. americana were conducted, respectively. Both pathogens showed host specificity, as suggested by the phylogenetic relationship and the host plants. In addition, disease control with carbendazim, trifloxystrobin, mancozeb, and prochloraz was assayed. All fungicides equally inhibited the mycelial growth of both pathogens.