The potential for genetic interaction between planted pastures of Cullen australasicum and natural populations of Cullen species

[Truncated abstract] Annual pastures in Australian agriculture are limited by dryland salinity and non-reliable rainfall resulting from climate change. In response to these limitations, perennial pasture crops are being developed for the wheat belt of Australia. Among these new perennial pasture crops is Cullen australasicum (Schltdl.) J.W.Grimes. A legume native to Australia, C. australasicum out-performed lucerne (Medicago sativa L.) in some field trials in low to mid-rainfall areas, and is currently included in a plant improvement program. The native range of C. australasicum overlaps parts of the Australian wheat belt. If paddocks of C. australasicum were established adjacent to natural populations of Cullen spp. then gene flow may occur between populations (Chapter 1). Furthermore, C. australasicum, as it is currently described, is interfertile with the three other recognized species of the Cullen patens-complex. The aim of this project was to determine whether the possibility of pollen from planted pastures of C. australasicum pollinating natural populations of C. patens-complex taxa warrants further study. Delineation of the species boundary of C. australasicum was addressed first (Chapter 2). Using DNA sequence data from the nrDNA ITS and two cpDNA regions, phylogenetic analysis was used to test the hypothesis that C. australasicum could not be genetically distinguished from the other three species in the C. patens-complex. The hypothesis was false; C. australasicum can be distinguished from C. discolor, C. patens and C. pallidum using sequence data. The four species of the C. patens-complex did not appear to be monophyletic...