Ecological restoration as an approach to promote crop production in semi-arid to arid regions
Research Outputs:
Several studies in the past proved various indigenous grass species suitable to rehabilitate sensitive disturbed ecosystems.
However, very little research had been done on the use of tree species in revegetation attempts. This study investigates Searcia lancea, known for being a hardy indigenous tree species with wide salt- and drought tolerance ranges, as a possible means in soil amelioration and reclamation. Current lacking baseline information on the ecology, morphology and physiology of this species are researched, before the suitability of this species for rehabilitation can be determined. Morphological malformations of floral structures, resembling the well-studied malformations found in mango (Mangifera indica), rouse questions of survival under straining conditions. It was found that the cause of malformations in S. lancea is not Fusarium spp., the well researched causal agent in Mango cultivars. However, diversity in fungal species found in malformed tissue, is still being identified.
One sample of malformed tissue tested positive for the presence of a phytoplasm, where after several other samples were also sequenced. The coincidence of insects present, prominently of the family Psyllidae, might indicate these insects as vectors of the phytoplasm present, although this relationship still has to be confirmed.
The main aim of this study is to determine whether Seacia lancea is suitable for use in rehabilitation attempts. Objectives involve gathering of baseline information on the physiology, morphology and population ecology of this species.
Malformed floral regions, resembling that of the closely related Mangifera indica (mango), proved to have a different cause than Fusarium spp. Sampled in different parts of South Africa (Bloemfontein, Kimberley, Christiana and Pretoria) it was noted that the malformations occur in clusters, both on the individual trees as well as in the population it was sampled. This may indicate that the causal agent is indeed biological. Furthermore, although the fungal species isolated from the tissue proved not to be Fusarium spp., the diversity of fungi isolated from the malformed tissue, is too extensive to be considered as prominent causal agents. However, a sample sequenced for the presence of phytoplasm DNA tested positive, after which several others were also sequenced.
Results of the latter DNA sequencing are still awaited. Insects as vectors of the biological causal agent were investigated, after which the family Psyllidae proved a prominent presence and are currently being identified at species level.
Ecophysiological investigations, which evaluates the impact the causal agent might have on the physiology of S. lancea, should also be included in the rehabilitation potential of this tree species. The quantitative measurements of the imbalance of hormones in the plants, as well as the presence of malformin, will be evaluated in the nearby future. The presence of malformin will be used as indicator of parasitic fungal presence. Recording baseline data for this tree species on morphological and physiologica level, may contribute to solutions of problematic relationships of the causal agent and the population ecology.
Malformed reproductive tissue may cause difficulty during the pollination process, which may lead to eventual decline in existing populations, or difficulty in establishment of populations in disturbed areas.
Posters
Swanepoel, J., Westcott, M., Bezuidenhout, J., & Gryzenhout, M. Karee (Searcia lancea) malformations a habitat of rich biodiversity. Poster presented at the Association for the Taxonomic Study of the Flora of Tropical Africa (AETFAT); Stellenbosch, South Africa, 13 January to 18 January 2014.