The Colletotrichum orbiculare species complex: Important pathogens of field crops and weeds

Colletotrichum orbiculare causes anthracnose of Cucurbitaceae and is phylogenetically closely related to pathogens of several other herbaceous hosts belonging to the Asteraceae , Fabaceae and Malvaceae . Most of them are known for their hemibiotrophic infection strategy and as destructive pathogens either of field crops or weeds. In order to study the phylogenetic relationships of these fungi, a multilocus analysis (ITS, GAPDH, CHS-1, HIS3, ACT, TUB2, GS) of 42 strains of C . orbiculare and related species was conducted. The analysis resulted in nine clades that confirmed the four species previously known as belonging to this species complex, C . lindemuthianum , C . malvarum , C . orbiculare and C . trifolii , and recognised four new species from weeds, namely C . bidentis , C . sidae , C . spinosum and C . tebeestii . The name C . orbiculare itself is widely used in plant pathology and science, but is invalid according to current nomenclatural rules. Therefore we described a new species with the same epithet and a type specimen that agrees with our current understanding of this species, and is linked to a living culture. Following the recent epitypification of C . lindemuthianum , we chose appropriate specimens with associated strains to serve as epitypes of C . malvarum and C . trifolii , and selected an authentic specimen of C . trifolii as lectotype.