Salsola tragus or S. australis (Chenopodiaceae) in Australia—untangling taxonomic confusion through molecular and cytological analyses
Catherine P. D. Borger A B D , Guijun Yan B , John K. Scott C , Michael J. Walsh B and Stephen B. Powles BA Department of Agriculture and Food, Western Australia, PO Box 432, Merredin, WA 6415, Australia.
B Western Australian Herbicide Resistance Initiative, School of Plant Biology, The University of Western Australia, 35 Stirling Hwy, Crawley, WA 6009, Australia.
C CSIRO Entomology, Private Bag 5, PO Wembley, WA 6913, Australia.
D Corresponding author. Email: cborger@agric.wa.gov.au
Australian Journal of Botany 56(7) 600-608 https://doi.org/10.1071/BT08043
Submitted: 13 March 2008 Accepted: 26 August 2008 Published: 26 November 2008
Abstract
Salsola tragus sensu lato (Chenopodiaceae) is found throughout Western Australia and is considered to be a weed in both natural and agricultural ecosystems, although the current taxonomic status of this species is not clear. The taxonomic literature reports morphological variation within Australian populations of the weed, indicating that there may be genetically distinct ecotypes or unidentified subspecies present within the species. A genetic and cytological approach was used to detect variation between 22 populations of S. tragus sensu lato in the south-west of Western Australia. Out-groups used in this study included a population of S. tragus L. from the USA and Maireana brevifolia (R.Br.) Paul G.Wilson (Chenopodiaceae) from Lake Grace. Four genetically distinct groups were identified, which were not closely related to the S. tragus out-group (~60% similarity). Further, these groups and a S. australis R.Br. sample from the USA were all diploid (2n = 18), unlike the tetraploid (2n = 36) S. tragus. The predominant wheatbelt weed, group A, which was previously classified as S. tragus ssp. tragus L., was identified as S. australis. This species is probably native to Australia, given its arrival predated European invasion. Further research is required to clarify the taxonomic status of the other three possible taxa and determine their status in relation to S. australis.
Acknowledgements
The authors thank the Grains Research and Development Corporation and the Department of Agriculture and Food, Western Australia, for the funding of a PhD scholarship to C. Borger. Advice and assistance in completing the work was provided by Dr Fred Hrusa, Dr Hu’aan Yang, Hiu Lui, Anna Williams and staff at the Western Australian Herbarium. The manuscript was improved by helpful comments from Dr Maurice MacDonald and the referees selected by Australian Journal of Botany.
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