Peronosclerospora australiensis sp nov and Peronosclerospora sargae sp nov., two newly recognised downy mildews in northern Australia, and their biosecurity implications

Morphological examination, supported by unnamed phylogenetic lineages found previously from DNA sequence analysis, revealed the presence of two new downy mildews on native Sorghum spp. in northern Australia. These species are formally described and illustrated as Peronosclerospora australiensis sp. nov. and Peronosclerospora sargae sp. nov. One of these species, P. australiensis, was also found on cultivated maize. Oospores of P. australiensis were present on shredded leaves of the native Sorghum spp., and conidia and conidiophores were found on maize leaves with chlorotic streaks. We review earlier reports of downy mildew on maize and native Sorghum species in northern Australia and show that many of these records represent P. australiensis. The biosecurity implications of the absence of some downy mildews on grasses from Australia as well as the detection of new cryptic species are discussed.