Nineteen Phaeoacremonium species are currently known in South Africa. These have been reported from grapevines, fruit trees, fynbos twig litter and arthropods. In other countries some of these ...Phaeoacremonium species are also known from hosts such as European olive, quince
and willow that commonly occur in the Western Cape Province of South Africa, where most South African records of Phaeoacremonium have been made. The aim of this study was to investigate the species diversity and host-range of Phaeoacremonium in the Western Cape Province of South
Africa by characterising 156 isolates collected from 29 woody hosts. Phylogenetic analyses of combined actin and beta-tubulin datasets allowed for the identification of 31 species among the 156 isolates, including 13 new species and 3 known species that had not been recorded in South Africa
previously. The new Phaeoacremonium species include P. album, P. aureum, P. bibendum, P. gamsii, P. geminum, P. junior, P. longicollarum, P. meliae, P. oleae,
P. paululum, P. proliferatum, P. rosicola and P. spadicum. All previous records of P. alvesii in South Africa were re-identified as P. italicum, but both species were recovered during this survey. A total of 35 described
Phaeoacremonium species are now known from South Africa, more than double the number reported from any other country. This high diversity reflects the high diversity of indigenous flora of the Cape Floral Region, a biodiversity hotspot mainly situated in the Western Cape Province. Paraphyly
and incongruence between individual phylogenies of the actin and beta-tubulin regions complicated species delimitation in some cases indicating that additional phylogenetic markers should be investigated for use in Phaeoacremonium phylogenies to prevent misidentifications and the introduction
of vague species boundaries.
Arthropod-mediated dispersal of pathogens is known in many cropping systems but has never been demonstrated for grapevine trunk disease pathogens. Arthropods from vineyards were screened for the ...presence of pathogens associated with Petri disease and esca using cultural and molecular techniques. The ability of the most abundant pathogen-carrying species to inoculate healthy grapevine vascular tissues was also determined. Millipedes and ants were allowed to associate with a DsRed- Express-transformed Phaeomoniella chlamydospora, after which they were exposed to freshly pruned healthy grapevines under controlled conditions and wounds were monitored for subsequent infection. In addition, the possibility of millipede excreta, commonly found on pruning wounds in the field, to act as inoculum source was determined. A diverse arthropod fauna was associated with declining grapevines and many of these carried trunk disease pathogens. However, spiders, the ant Crematogaster peringueyi, and the millipede Ommattoiulus moreleti were the most abundant pathogen carriers. The ant and millipede species fed on pruning wound sap and effectively transmitted trunk disease pathogens. Millipede excreta contained viable spores of Phaeomoniella chlamydospora and may serve as an inoculum source. Numerous arthropods, including beneficial predators, are potential vectors of grapevine trunk disease pathogens. Our results highlight the need for an integrated approach, including targeted management of ants and millipedes at the time of pruning, to limit the spread of grapevine trunk diseases.
Persimmon trees with dieback symptoms and cankers were observed in three production areas in Western Cape Province in South Africa. Isolations were made from diseased branches, cankers, and pruning ...wounds as well as fungal fruiting bodies on dead branches and old pruning wounds. Several trunk disease pathogens were identified based on morphological characteristics and by molecular methods, including Diaporthe eres, D. infecunda, Eutypella citricola, E. microtheca, Phaeoacremonium parasiticum, P. scolyti, P. australiense, P. minimum, Fomitiporia capensis, Fomitiporia sp., Fomitiporella sp., and Inocutis sp., which were isolated from persimmon for the first time in the world. Other first reports from persimmon in South Africa include D. foeniculina, D. ambigua, D. mutila, Diaporthe sp., Neofusicoccum australe, N. parvum, Diplodia seriata, and Eutypa lata. Pathogenicity tests conducted with all species, except the basidiomycetes, confirmed their status as possible persimmon pathogens. This is the first study to determine and identify fungi associated with diseased persimmon in South Africa. The knowledge gained in this study forms the basis for further research to determine the impact of these fungi on persimmon productivity.
Trunk disease fungal pathogens reduce olive production globally by causing cankers, dieback, and other decline-related symptoms on olive trees. Very few fungi have been reported in association with ...olive dieback and decline in South Africa. Many of the fungal species reported from symptomatic
olive trees in other countries have broad host ranges and are known to occur on other woody host plants in the Western Cape province, the main olive production region of South Africa. This survey investigated the diversity of fungi and symptoms associated with olive dieback and decline in
South Africa. Isolations were made from internal wood symptoms of 145 European and 42 wild olive trees sampled in 10 and 9 districts, respectively. A total of 99 taxa were identified among 440 fungal isolates using combinations of morphological and molecular techniques. A new species of
Pseudophaeomoniella, P. globosa, had the highest incidence, being recovered from 42.8 % of European and 54.8 % of wild olive samples. This species was recovered from 9 of the 10 districts where European olive trees were sampled and from all districts where wild olive trees were
sampled. Members of the Phaeomoniellales (mainly P. globosa ) were the most prevalent fungi in five of the seven symptom types considered, the only exceptions being twig dieback, where members of the Botryosphaeriaceae were more common, and soft/white rot where only
Basidiomycota were recovered. Several of the species identified are known as pathogens of olives or other woody crops either in South Africa or elsewhere in the world, including species of Neofusicoccum, Phaeoacremonium, and Pleurostoma richardsiae. However, 81 of
the 99 taxa identified have not previously been recorded on olive trees and have unknown interactions with this host. These taxa include one new genus and several putative new species, of which four are formally described as Celerioriella umnquma sp. nov., Pseudophaeomoniella globosa
sp. nov., Vredendaliella oleae gen. & sp. nov., and Xenocylindrosporium margaritarum sp. nov.
Extracts of plant species, used traditionally to treat malaria, have been extensively investigated for their activity against Plasmodium intraerythrocytic asexual parasites in search of new ...antimalarial drugs. However, less effort has been directed towards examining their efficacy in blocking transmission. Here, we report the results of the in vitro screening of extracts from eight selected plant species used traditionally to treat malaria in South Africa for activity against Plasmodium falciparum NF54 early and late stage gametocytes. The species used were Khaya anthotheca, Trichilia emetica, Turraea floribunda, Leonotis leonurus, Leonotis leonurus ex Hort, Olea europaea subsp. Africana, Catha edulis and Artemisia afra.
To investigate the activities of extracts from plant species traditionally used for malaria treatment against P. falciparum gametocytes.
Air-dried and ground plant leaves were extracted using acetone. Primary two point in vitro phenotypic screens against both early and late stage gametocytes were done at 10 and 20µg/ml followed by full IC50 determination of the most active extracts. Inhibition of gametocyte viability in vitro was assessed using the parasite lactate dehydrogenase (pLDH) assay.
Of the eight crude acetone extracts from plant species screened in vitro, four had good activity with over 50–70% inhibition of early and late stage gametocytes’ viability at 10 and 20µg/ml, respectively. Artemisia afra (Asteraceae), Trichilia emetica (Meliaceae) and Turraea floribunda (Meliaceae) were additionally highly active against both gametocyte stages with IC50 values of less than 10µg/ml while Leonotis leonurus ex Hort (Lamiaceae) was moderately active (IC50<20µg/ml). The activity of these three highly active plant species was significantly more pronounced on late stage gametocytes compared to early stages.
This study shows the potential transmission blocking activity of extracts from selected South African medicinal plants and substantiates their traditional use in malaria control that broadly encompasses prevention, treatment and transmission blocking. Further studies are needed to isolate and identify the active principles from the crude extracts of A. afra, T. emetica and T. floribunda, as well as to examine their efficacy towards blocking parasite transmission to mosquitoes.
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This study presents a novel framework for the design of reinforced concrete (RC) structures which aims at ensuring that future RC structures have the lowest possible carbon footprint, energy use and ...impact on the environment. The key focus of the study is on RC structures where there is often a lack of grasp of materials aspects, and environmental aspects of construction. In the proposed framework, a set of quantifiable design parameters and variables (binder type, concrete grade, diffusivity, concrete cover depth, area of steel in the structural component) are selected with respect to a set of performance measures which cover the functionality and availability of the structure to the user during its service life. The outputs generated from the framework are optimised material types and properties which not only meet the design performance requirements but also lead to minimised life-cycle environmental impacts. A RC beam is used to demonstrate the proposed design methodology. The application of the framework for design in the material specifications of the RC beam showed a reduced volume of materials in construction compared to the current materials and structures design practice.
Natural steel corrosion of reinforced concrete (RC) structures is a slow process which researchers find necessary to accelerate in laboratory tests to obtain needed damage in a short time. ...Regrettably, there is no standard procedure for accelerating steel corrosion in RC specimens. Researchers therefore continue to use various techniques to accelerate it. Unfortunately, structural damage and rate of steel corrosion are dependent on the accelerated corrosion technique used. Despite that, results obtained by researchers are applied by structural engineers and asset managers to in-service structures. This paper reviews previous techniques used to accelerate steel corrosion. Where possible it proposes standard procedures to accelerate steel corrosion. In other instances it points out needed further research. One of the procedures recommended in the paper is to contaminate selected faces of RC specimens with chlorides, as opposed to immersing samples in NaCl solution or adding chlorides to concrete mixes. It is also recommended to allow specimens to sufficiently dry during steel corrosion so as to promote steel corrosion.
The concept of structural health monitoring has been the subject of research over the last few years, particularly in civil and structural engineering where ageing infrastructure is of major concern. ...These studies have led to initiatives towards the development and deployment of new sensing technologies. Owing to the harsh environments found in the construction industry, and the large size of civil engineering structures, such sensors should be robust, rugged, easy to use and economical. Fiber Bragg grating (FBG) sensors offer a viable such sensing approach with a number of advantages over traditional sensors. These include immunity to electromagnetic interference, light weight, small size, multiplexing capabilities, ease of installation and durability. This paper reports some results from a multi-disciplinary research program on FBG sensors involving the School of Civil and Structural Engineering and the School of Electrical and Electronic Engineering at Nanyang Technological University in Singapore. Novel FBG strain sensors have been developed and deployed on highway bridges to measure dynamic strain, static strain, and temperature. Results of these studies indicate that, if properly packaged, FBG sensors can survive the severe conditions associated with the construction environments of civil infrastructure.
To show the application of the chloride conductivity index test in service life prediction (SLP) using both the deemed-to-satisfy and probabilistic approaches to performance-based durability design. ...It is desirable to adopt a performance-based approach with respect to durability design of reinforced concrete (RC) structures. This is based on the perception that the durability of RC is achieved when the limiting value from an established test method is met. In South Africa, the durability index (DI) approach has been developed, which permits performance-based specifications for durability of RC. This approach involves the application of a test method together with a SLP model. This integrated approach links material properties directly with the expected service life of RC structures and environmental conditions. Two DIs are relevant to degradation processes in RC: the chloride conductivity index which is related to chloride ingress, and the oxygen permeability index related to carbonation. The study presented here focuses on the application of the chloride conductivity index as the main input parameter of a SLP model concerned with chloride-induced reinforcement corrosion. The methodology and output of the SLP model as applied in the deemed-to-satisfy approach are compared with those of the probabilistic approach. Both approaches are exemplified using a concrete pier cast in situ in a marine environment. The performance-based durability specifications from the deemed-to-satisfy approach are found to be more conservative compared to those of the probabilistic approach.
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