Large-spored Alternaria pathogens in section Porri disentangled

The omnipresent fungal genusAlternariawas recently divided into 24 sections based on molecular and morphological data.Alternariasect.Porriis the largest section, containing almost allAlternariaspecies with medium to large conidia and long beaks, some of which are important plant pathogens (e.g.Alternaria porri, A. solaniandA. tomatophila). We constructed a multi-gene phylogeny on parts of the ITS, GAPDH, RPB2, TEF1 and Alt a 1 gene regions, which, supplemented with morphological and cultural studies, forms the basis for species recognition in sect.Porri. Our data reveal 63 species, of which 10 are newly described in sect.Porri, and 27 species names are synonymised. The three knownAlternariapathogens causing early blight on tomato all cluster in one clade, and are synonymised under the older name,A. linariae.Alternaria protenta, a species formerly only known as pathogen onHelianthus annuus, is also reported to cause early blight of potato, together withA. solaniandA. grandis. Two clades with isolates causing purple blotch of onion are confirmed asA. alliiandA. porri, but the two species cannot adequately be distinguished based on the number of beaks and branches as suggested previously. This is also found among the pathogens ofPassifloraceae, which are reduced from four to three species. In addition to the known pathogen of sweet potato,A. bataticola, three more species are delineated of which two are newly described. A newAlternariasection is also described, comprising two large-sporedAlternariaspecies with concatenate conidia.