Taxonomy and phylogeny of fungi causing tar spot on ficus religiosa in Chiang Mai Province

Abstract

Tar spot is a common fungal disease often found in tropical and damp areas. They mostly exist in Asian countries like Thailand, and the symptoms usually occur on leaves, stems, and fruits. Only a few significant studies about this fungus are available because of their biotrophic nature, which makes them unable to grow in culture, therefore, sequence data from fresh collections are difficult to obtain. On one hand, most studies recorded this disease to be caused by the genus Phyllachora. On the other hand, some Tar spot symptoms are known to be caused by other genera, and there are still several Tar spot infestations in which the causal agent is yet to identify. In Thailand, the Bodhi tree plays an important role in culture and historic preservation. However, the Bodhi tree has been facing a dilemma due to attacks of pathogens, particularly on the leaves, which serve as the center of its beauty. This study aimed to identify the causal agent of the Tar spot on Bodhi tree leaves taken from different locations around Chiang Mai province, northern Thailand, through morpho-molecular evaluation. We isolated eight leaf samples of Ficus religiosa taken from Chiang Mai, Thailand. Symptoms on the host appear as black, solitary to gregarious, mainly on the upper surface. Pseudostromata is elongated, irregular, discrete, sparse, coalescent, glabrous, shiny, intraepidermal to subepidermal, epiphyllous, multilocular, occasionally amphigenous, rarely covering the leaf surface. Morphologically the new species was characterized by pseudostromatic ascomata with ostiole, septate paraphyses, cylindrical to fusiform asci, and globose to elliptical ascospores with sometimes 1-2 guttules, central concave depression present mostly in the globose form, a mucilaginous sheath that is irregularly thickened and widely thickened in the lateral part. The asexual morph produces ellipsoidal and hyaline conidia. The newly g obtained sequences were positioned within Neophyllachora and formed a distinct clade but close to Neophyllachora fici with high bootstrap support in the phylogenetic analyses. In addition, both species are reported in the same host genus (Ficus) but with different locality (Thailand Vs. Taiwan). Further the synopsis table for Neophyllachora and the identification key to the genus are provided.