Revision of the rust genus Uromyces on Cucurbitaceae

This study revises Uromyces (Pucciniales or Uredinales) on the economically important plant family Cucurbitaceae and presents descriptions, illustrations and a key to aid determination of the 17 recognized species and four varieties. Seven species are described as new: Uromyces aimeae, U. aquiriensis, U. cucumivorus, U. infarctus, U. naucinus, U. saulensis and U. superstomatalis. Uromyces novissimus occurs on a number of tribes of Cucurbitaceae and is broadly circumscribed as a variable species that comprises four varieties. Variety cissampelidis, var. hellerianus and var. pentastriatus, are new combinations for U. cissampelidis, U. hellerianus and U. pentastriatus that have been regarded so far either as synonyms of U. novissimus or distinct species. The new name U. ernesti-ulei is proposed to replace the illegitimate name U. cayaponiae that refers to a uredinial state. It has been synonymized with U. novissimus as well but is considered a distinct species. Uromyces reynoldsii is reduced to a synonym of U. yakushimensis and a lectotype is selected for U. guraniae. Uromyces aimeae, U. neotropicalis and U. superstomatalis differ from the remaining species in superstomatal uredinia and telia and appear to be the first Uromyces spp. in which such sori are reported. The chytrid Olpidium uredinis is reported from three species, U. ernesti-ulei, U. guraniae and U. novissimus var. hellerianus, which are new hosts of this mycoparasite.