Phytophthora tropicalis: Causal agent of persimmon fruit rot in Brazil

Persimmon fruit (Diospyros kaki L.) from commercial orchards located in southern Brazil, in Curitiba, Parana, showed dark firm rot. The incidence in the field was about 2% in an evaluation in the 2016 growing season, and from these infected fruit, three Phytophthora sp. isolates were obtained. Therefore, this study aimed to identify the causal agent of the disease through morphophysiological and molecular analysis of the isolates. Initially, the pathogenicity test was performed on persimmon fruit to fulfil Koch's postulates. Mycelial growth at eight temperatures ranging from 8 degrees C to 35 degrees C was evaluated for taxonomic purposes. Next, the morphological characteristics of sporangia, chlamydospores and oospores were evaluated. For molecular characterization, sequencing of the ITS-rDNA region and portions of the COXI and TEF1 alpha genes and phylogenetic analysis were performed. All isolates were pathogenic, causing symptoms of firm and dark rot similar to those observed in the orchards. Mycelial growth was not observed at 35 degrees C. There was an abundant production of ellipsoid, papillate, deciduous sporangia with long pedicels and the formation of globose chlamydospores. The isolates were heterothallic, all belonging to group A1, in which the production of plerotic oospores with amphigenous antheridia was verified. The morphophysiological and molecular characterization allowed the identification of the isolates as Phytophthora tropicalis. To our knowledge, this is the first report of persimmon fruit rot caused by P. tropicalis.

Automated summary

Persimmon fruit from commercial orchards in southern Brazil was found to have dark firm rot. This study identified the causal agent as Phytophthora tropicalis through morphophysiological and molecular analysis of the isolates.