Identification of eight Panicum species in Riverina region of NSW using DNA sequence analysis

Australia has over 30 Panicum spp. (panic grass) including several non-native species that cause crop and pasture loss due to competition. To develop appropriate management strategies for each species, it is critical to correctly identify panic grass species encountered. Currently, panic grass identification relies on microscopic examination of the inflorescence and spikelets, an approach that is only useful for flowering specimens and requires significant taxonomic expertise. To overcome this limitation, we applied both morphological and molecular techniques for identification of Panicum spp. in the Riverina region of New South Wales. We identified three molecular markers: one nuclear gene region (ITS) and two chloroplast gene regions (matK and trnL intron-trnF) capable of differentiating eight Panicum spp. Concatenation of sequences from ITS, matK and trnL intron-trnF gene regions provided clear separation of eight species collected regionally and identified a maximum intraspecific distance of 0.22% and minimum interspecific distance of 0.33%. Based on comparison with verified voucher specimens, P. hillmanii Chase was prevalent and constituted 78.9% of all samples collected and identified. DNA barcoding represents an accurate and potentially cost effective tool for distinguishing Panicum spp. at the species level regardless of growth stage. Molecular markers may also be useful for accurate demographic analysis of Panicum grass invasion in Australia and abroad