Molecular phylogenetics of four Australian broomrapes (Orobanche: Orobanchaceae) insights into taxonomy informing environmental management and biosecurity

A project undertaken at the State Herbarium of South Australia and The University of Adelaide and supervised by Ed Biffin

Project team: Dr. Ed Biffin, Dr. Bill Barker (State Herbarium of South Australia) and Professor Michelle Waycott (The University of Adelaide and State Herbarium of South Australia)

Broomrapes (Orobanche species) are root parasites of flowering plants and include some of the worlds’ most destructive agricultural weeds. In Australia, four species are recognised including taxa that elsewhere in their range are considered serious pests of several important crops. Management agencies have already implemented a costly eradication programme for one of the Australian species. However, the level of threat posed by this, and the other Australian occurrences is poorly understood, in part reflecting taxonomic uncertainty and the complex nature of the global taxonomy of Orobanche and diverse host-parasite interactions at the specific and infraspecific level.

We are investigating the taxonomy and evolutionary relationships of the Australian species including one naturalised, one native and two species of questionable origins and affinities. We will use modern taxonomic methods, including morphological and ecological (host-preference) data and comparative analyses of molecular markers generated using next-generation sequencing.

The overall objectives are:

  1. to establish the identity of the Australian species in the context of the global distribution of the genus; and
  2. to develop a suite of molecular tools that can be readily applied to the study of Orobanche at and below the species level, enabling questions such as population status, invasion pathways and frequency of introduction to begin to be addressed.
The anticipated outcomes of this project will be a refined knowledge of the taxonomy and evolutionary relationships of Orobanche, and particularly the Australian species. Our molecular approach will provide a permanent resource for rapid genetic assessment and identification of economically important Orobanche species, will help inform management of Australian Orobanche and provide impetus for further study, both within Australia and globally.

Figure 1. Orobanche minor growing with nasturtium. (Photo: W.R. Barker)

Figure 2. Orobanche cernua var. australiana attached to the roots of a native Senecio (Photo: W.R. Barker)

Figure 3. A recently discovered population of Orobanche in the upper Murray catchment may be a new species, shown with broad leaves of native Hydrocotyle host (Photo: W.R. Barker)