Diseases and pests of Encephalartos species in South Africa

Diseases and pests of Encephalartos species in South Africa

214 Abstracts ones. Special attention therefore needs to be given to invasive alien plant species before they can lead to the extinction of native p...

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214

Abstracts

ones. Special attention therefore needs to be given to invasive alien plant species before they can lead to the extinction of native plants species. doi:10.1016/j.sajb.2015.03.167

Diseases and pests of Encephalartos species in South Africa R. Nesamari, T.A. Coutinho, J. Roux Department of Microbiology and Plant Pathology, DST & NRF Centre of Excellence in Tree Health Biotechnology (CTHB), University of Pretoria, Private Bag X20, Hatfield, Pretoria 0028, South Africa

areas amongst the study area where the height, diameter and distance between species were measured. The results obtained show that P. alba has great effects on the growth of native grass, as there were differences between populations inside the patch and away from the patch. P. alba can co-exist as there are some grass species inside its population but it affects the growth of grass species as their height is different with that of the species outside the population. doi:10.1016/j.sajb.2015.03.169

Antifungal activity of the selected medicinal plants used to treat candidiasis

The cycad genus, Encephalartos, is endemic to Africa with more than half of its species occurring in South Africa. Seventy-three percent of South African Encephalartos species are threatened with extinction with four species already extinct in the wild. The major threat to Encephalartos species in South Africa is the illegal trade of cycads. In addition, biotic factors, such as insect pests and microbial diseases that affect these plants, are on the increase. The aim of this study was to identify diseases and insect pests of Encephalartos species in South Africa. Symptomatic plant material and insects were collected from diseased cycad species in the KwaZulu-Natal, Limpopo and Gauteng provinces. Microbial isolates obtained were identified based on morphology and DNA sequence data. Species of Alternaria, Phoma and Pseudocercospora were often isolated from leaf spots and Bionectria and Fusarium species from dying cycads. The plant pathogen, Phytophthora cinnamomi, was isolated from dying Encephalartos tranvenosus plants in the Modjadji cycad reserve in Limpopo. Insect pests observed causing the most damage to cultivated cycads were the beetle, Amorphocerus talpa, and the scale insect, Aspidiotus capensis. A. talpa was observed infesting cycad cones in the Pretoria Botanical Gardens, causing discolouration and death of the cones. The scale insect, A. capensis, was found on the leaflets of many cycads, causing chlorosis and premature death of leaves. In this study we also report, for the first time, the scale insect, Aulacaspis yasumatsui, infesting cycads in South Africa. A. yasumatsui was identified based on morphology and DNA sequence data. Plants infested by this scale insect showed symptoms of severe leaf chlorosis and necrosis. The presence of A. yasumatsui on South African Encephalartos species is of much concern and efforts should be made to manage this pest in the country.

The aim of the study was to investigate the antifungal activities of the selected plants used traditionally for the treatment of candidiasis. Leaves of five plant species (Ehretia rigida, Ximenia americana, Anthocleista grandiflora, Artabotry branchypetalus and Sarcostemma viminale) were extracted with distilled water and acetone. The latter were tested against six isolates of Candida species (Candida albicans, Candida parapsilosis, Candida glabrata, Candida tropicalis, Candida krusei and Cryptococcus neoformans). The antifungal activity was conducted using microdilution method. Clotrimazole and acetone were used as positive and negative controls respectively. The plant extracts were tested for the antioxidant activity using DPPH qualitative assay. Acetone extracts of A. grandiflora, X. americana and A. branchypetalus were moderatively active with MIC values ranging from 0.31 mg/ml to 0.63 mg/ml. Aqueous plant extracts had very weak activity against the test organisms with MIC values ranging from 0.63 mg/ml to 1.25 mg/ml. Acetone plant extracts inhibited the growth of the Candida species better than aqueous plant extracts. Minimum inhibitory concentrations (MIC) of the positive control (Clotrimazole) against the test organisms ranged from 0.04 to 0.08 mg/ml. Acetone plant extracts also showed high antioxidant activity than the aqueous plant extracts. The results of this study showed that some of the selected medicinal plants can be potential sources of antifungal agents and validate their use in the traditional medicine to some extent.

doi:10.1016/j.sajb.2015.03.168

doi:10.1016/j.sajb.2015.03.170

The interaction and co-existence of alien plant species Populus alba L. with native grass species

Assessment of potential invasiveness of Verbascum thapsus L. in South Africa

P.N. Nesengani, M.H. Ligavha-Mbelengwa Deparment of Botany, School of Mathematical and Natural Sciences, University of Venda, Private Bag X5050, Thohoyandou 0950, South Africa

Z. Ntantiso, T.P. Jaca Invasive Species Programme, South African National Biodiversity Institute, Private Bag X101, Pretoria 0001, South Africa

Populus alba is a tree species which is a fast grower that is distributed naturally on the bank of rivers in arid, and semi-arid regions and it is naturally found on a variety of soil types, being tolerant to pollution. It is geographically extended mainly in Asia and Africa. Populus alba is a member of the willow family (Salicaceae) that is native to Eurasia. The main objective of the study was to have clear understanding on how P. alba may affect or benefit the indigenous grass species. The study was conducted on a study site along the N1 south road where there were two patches of P. alba species, one on the left right hand side of the road N1 south and the one on the left. The Quadrat method was used to sample different

K.V. Nkuna, N.A. Masevhe School of Maths and Natural Sciences, Department of Botany, University of Venda, Private Bag X5050, Thohoyandou, South Africa

Verbascum thapsus (common mullein) is a hairy biennial herb with rosette leaves in the first year. It is native to Europe and naturalized in temperate areas of the world, including North America, Hawai'i, Australia, and New Zealand. The plant spreads through production of numerous seeds (up to 180,000) per plant, which are produced during the second year of growth. In South Africa, V. thapsus was first observed naturalised in Gauteng Province at Rietfontein, Bronberg Conservancy and has since been recorded in areas around northern Free State and Northern Cape Province. The species is not yet listed as invasive in the country; it is listed as a suspect candidate that needs evaluation. The aim of this study was to assess the invasiveness of V. thapsus in South Africa. Australian/New