Skip to main content
ARS Home » Plains Area » Sidney, Montana » Northern Plains Agricultural Research Laboratory » Pest Management Research » Research » Publications at this Location » Publication #305186
Title: Evidence of Tamarix hybrids in South Africa, as inferred by nuclear ITS and plastid trnS-trnG DNA sequences

Author
item MAYONDE, GUETOR - University Of Witwatersrand
item CRON, G - University Of Witwatersrand
item Gaskin, John
item BYRNE, M - University Of Witwatersrand

Submitted to: South African Journal of Botany
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/17/2014
Publication Date: 1/1/2015
Publication URL: http://handle.nal.usda.gov/10113/60098
Citation: Mayonde, G., Cron, G.V., Gaskin, J.F., Byrne, M.J. 2015. Evidence of Tamarix hybrids in South Africa, as inferred by nuclear ITS and plastid trnS-trnG DNA sequences. South African Journal of Botany. 96:122-131.

Interpretive Summary: Tamarix usneoides (Tamaricaceae) is a plant species native to southern Africa where it is currently being used in the mines for to help collect toxic chemicals from mine waste piles. However, there are also some other Tamarix species that are invasive in southern Africa. The exotic Tamarix species are thought to be hybridizing among themselves and with the native species. Accurate identification of Tamarix is of great importance in southern Africa because of the invasive potential of T. ramosissima and also the potential usefulness of T. usneoides in mining. In this study, we use DNA to determine if the native and invasive Tamarix are hybridizing. Close to 45% of Tamarix genotypes were hybrids with more than 50% of them occurring on the mines. The outcome of this study will ensure that only pure native T. usneoides is propagated for planting on the mines in South Africa in the future and that a proper control measure of the alien invasive Tamarix is used.

Technical Abstract: Tamarix usneoides (Tamaricaceae) is a species native to southern Africa where it is currently being used in the mines for phytoremediation. However, Tamarix aphylla, T. ramosissima, T. chinensis, and T. parviflora have been reported as exotic species in South Africa, with T. ramosissima declared invasive here. The exotic Tamarix species are hypothesized to be hybridizing among themselves and with the indigenous species. Accurate identification of Tamarix is of great importance in southern Africa because of the invasive potential of T. ramosissima and also the potential usefulness of T. usneoides. In this study, nuclear DNA sequence markers (ITS1 and ITS2 regions), together with the plastid marker trnS–trnG, are used to identify the genetic distinctiveness of Tamarix species and their putative hybrids. Phylogenies based on the ITS and trnS-trnG regions revealed that the indigenous T. usneoides is genetically distinct from the exotic species, which, however, could not clearly be separated from each other. The lack of congruence (p>0.0001) in the ITS and trnS-trnG phylogenies suggest that there is high incidence of hybridization in Tamarix populations in South Africa. Importantly, molecular diagnosis of Tamarix was able to identify hybrids using polymorphisms and phylogenetic signals. Close to 45% of Tamarix genotypes were hybrids with more than 50% of them occurring on the mines. Spread of Tamarix hybrids in South Africa through phytoremediation could enhance invasiveness. Therefore, the outcome of this study will ensure that only pure indigenous T. usneoides is propagated for planting on the mines in South Africa and that a proper control measure of the alien invasive Tamarix is used. Interestingly, the molecular diagnosis of Tamarix species supported the preliminary morphological identification of the species using eight key characters, although the molecular markers used were not informative enough to separate hybrids from their closely related parent species. However, hybrids were more reliably identified using polymorphisms and phylogenetic signal than morphological features.