Diaporthe rosiphthora sp. nov.: Yet another rose dieback fungus

Abstract

The cultivated rose (Rosa × hybrida) is the most important plant species in the cut flower industry worldwide. In Brazil, rose plantations are said to be frequently attacked by a dieback disease of uncertain etiology. A severe rose dieback outbreak was detected and closely observed in Viçosa (state of Minas Gerais, Brazil). The disease was particularly severe on the cultivar ‘Gran Gala’. A fungus with typical characteristics of the asexual state of Diaporthe spp. was regularly associated to necrotic tissues and isolated in pure culture. Morphology of the fungus was examined and described and DNA was extracted for molecular studies. Phylogenetic analysis inferred from combined dataset of the internal transcribed spacer ribosomal DNA (ITS), partial calmodulin gene (CAL) and partial translation elongation factor 1-α (TEF1) along with morphological characterization, indicated that the fungus causing dieback disease of Rosa × hybrida is a new species of Diaporthe. This is described herein as Diaporthe rosiphthora sp. nov. Its pathogenicity to Rosa × hybrida was evaluated and inoculations on additional selected rose cultivars indicated that, besides ‘Grand Gala’, another important commercial cultivar (‘Saltinho’) is susceptible. Cultivars ‘Greta’ and ‘Príncipe Negro’, were also susceptible, though less so than ‘Grand Gala’ and ‘Saltinho’. Diaporthe rosiphthora is a novel addition to the numerous fungi associated rose dieback.