Six Species of <i>Diaporthe</i> Associated with Phomopsis Stem Canker of Sunflower in Southern Pampean Region of Argentina

A survey of 67 commercial fields in 19 locations was conducted the southern Pampean region Argentina for Phomopsis stem canker sunflower (Helianthus annuus L.) between 2014 and 2019. total 210 plants having typical symptoms were randomly sampled, fungal isolation performed. Of 187 isolates Diaporthe that recovered, 94% showed morphological characteristics similar to D. helianthi, 3% gulyae, 1% caulivora, sojae, 0.5% kongii, longicolla. Following characterization, identity six morpho-species confirmed by phylogenetic analyses ?-tubulin, translation elongation factor 1-?, internal transcribed spacer gene regions. Koch’s postulates completed fungi inoculating one susceptible hybrid with isolate each species using stem-wound inoculation method. Seven days postinoculation, significant differences disease severity observed (P &lt; 0.0001), helianthi gulyae causing significantly greater severity. To our knowledge, this is first report longicolla, sojae associated Argentina.