MOLECULAR MARKER TOOLS FOR THE IDENTIFICATION OF WEEDY SPOROBOLUS SPECIES IN AUSTRALIA

Nine species of Sporobolus having overlapping morphological characteristics have been included in ‘Sporobolus indicus complex’. Five of these nine species are noxious weeds in various states of Australia. These species are major constraints to pasture production causing significant losses in the dairy and beef industries. In this study, a DNA-based molecular investigation was undertaken to help develop improved integrated management strategies for these noxious weeds. This study employed 40 Sporobolus seed collections coming from 14 species. Polymerase Chain Reaction (PCR) based Random Amplified Polymorphic DNA (RAPD) analysis generated a series of species-specific molecular markers that can be employed for the identification purpose. However, as the technique was highly sensitive to PCR reaction and cycling conditions, an alternative molecular approach, involving DNA sequencing of Internal Transcribed Spacers (ITS) of nuclear Ribosomal DNA (rDNA) repeat units was employed to develop a diagnostic tool for these species. The rDNA ITS sequencing approach could also be used for a phylogenetic study which revealed clear cut boundary between the weedy and the non-weedy species within the ‘S. indicus complex’. In addition to the molecular phylogenetic study, PCR-Restriction Fragment Length Polymorphism (RFLP) approach was used to develop a diagnostic tool for the weedy species. Using this approach, single restriction enzyme (MvnI) was identified which could discriminate all five noxious weedy species from all others. The molecular genetic and phylogenetic information thus generated and the molecular diagnostic tool thus developed from this study can be effectively utilized for the integrated management of these noxious weeds in Australia.