Submitted to: Mycologia
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/20/2016
Publication Date: 2/6/2017
Citation: Demers, J.E., Liu, M., Hambleton, S., Castlebury, L.A. 2017. Rust fungi on Panicum. Mycologia. 109(1):1-17. doi: 10.1080/00275514.2016.1262656. Interpretive Summary: Rust fungi cause diseases on many different plants and significant yield losses in many crops. Rust is a major disease of switchgrass, which is increasingly grown to produce biofuel ethanol, a renewable energy source. Infection of switchgrass by rust fungi can decrease yields of both biomass and ethanol. Using DNA sequences and spore characteristics, we identified five species of rust fungi that can infect switchgrass, three of which are new to science. This information will allow plant pathologists and switchgrass growers to identify and manage diseases on switchgrass. This research will also enhance efforts to breed disease resistant switchgrass varieties, the principal method used to manage rust diseases.
Technical Abstract: Rusts are economically important diseases of switchgrass and other Panicum grasses. Phylogenetic analyses based on sequences of the rDNA internal transcribed spacer ITS2 region, the large subunit, and the intergenic spacer region (IGS) showed that species of rust fungi infecting switchgrass are closely related within Puccinia. Variation among rbcLa sequences for the associated hosts sampled concurred with the original identifications. Five species infecting switchgrass were recognized: Puccinia graminicola (= Uromyces graminicola), P. pammelii, and the proposed new species P. amara, P. novopanici, and P. pascua. These species were distinct from P. emaculata, the species previously considered the principal rust pathogen infecting switchgrass but that was found exclusively on witchgrass in this study. Rust fungi on switchgrass previously identified as P. emaculata were identified as the morphologically similar species P. amara, P. novopanici, and P. pammelii (= P. panici). The morphological species Puccinia graminicola was found to comprise three species, P. graminicola and the proposed new species P. pascua on switchgrass and P. cumminsii on Panicum sp.