Agricultural Research Council Infruitec Nietvoorbij

Stellenbosch, South Africa

Agricultural Research Council Infruitec Nietvoorbij

Stellenbosch, South Africa
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Lamprecht R.L.,Stellenbosch University | Maree H.J.,Stellenbosch University | Maree H.J.,Agricultural Research Council Infruitec Nietvoorbij | Stephan D.,Stellenbosch University | Burger J.T.,Stellenbosch University
Virus Genes | Year: 2012

The complete sequences of RNA1 and RNA2 have been determined for a South African isolate of Grapevine fanleaf virus (GFLV-SAPCS3). The two RNAs are, respectively, 7,342 and 3,817 nucleotides in length, excluding the poly(A) tails. RNA1 has a large open reading frame (ORF) of 6,852 nucleotides and a 50-UTR and a 30-UTR of 243 and 244 nucleotides, respectively. RNA2 encodes for an ORF of 3,330 nucleotides and has the highest nucleotide identity (90.4 %) with GFLV-F13. The full length nucleotide sequence of GFLV-SAPCS3 RNA1 had the highest nucleotide identity (86.5 %) to the French isolate GFLV-F13. The 50- and 30-UTRs of GFLV-SAPCS3 RNA2 are 272 nucleotides and 212 nucleotides (nt) in length, respectively. The GFLV-SAPCS3 RNA2 50-UTR is 32-53 nt longer compared to other GFLV isolates. The GFLV-SAPCS3 RNA2 50-UTR is also more closely related to GFLV-GHu and Arabis mosaic virus (ArMV) isolates than to other GFLV isolates. Putative intra- and interspecies recombination events between GFLV and ArMV isolates involving GFLV-SAPCS3 RNA1 and RNA2 were investigated. Recombination analysis software has indicated that the GFLV-SAPCS3 50-UTR might have evolved from a recombinational event between GFLV-F13-type and ArMV-Ta-type isolate. © Springer Science+Business Media, LLC 2012.

Daniel C.K.,Stellenbosch University | Daniel C.K.,Agricultural Research Council Infruitec Nietvoorbij | Lennox C.L.,Stellenbosch University | Vries F.A.,Agricultural Research Council Infruitec Nietvoorbij
Postharvest Biology and Technology | Year: 2014

Curative and protective applications of garlic extracts and clove oil directly or through volatile exposure were tested in vivo for potential to inhibit decay caused by postharvest pathogens Botrytis cinerea, Penicillium expansum and Neofabraea alba on three apple cultivars, 'Granny Smith', 'Golden Delicious' and 'Pink Lady'. Curative application of the extracts by direct exposure proved to be more effective than a protective application for decay management of B. cinerea and P. expansum on all three cultivars. The efficacy of garlic extracts and clove oil, individually, as well as a combination treatment, did not differ significantly (. P<. 0.05) from each other; however, all treatments significantly (. P≤. 0.05) reduced decay when compared to the control treatments. Direct exposure of fruit that were artificially inoculated with N. alba, to the extracts, did not result in any inhibition compared to the control treatments. Exposure of inoculated fruit to the volatiles of the extracts did not inhibit postharvest decay on any of the apple cultivars, and in some cases, resulted in increased lesion diameters. This study demonstrated that the curative application of garlic extracts has the potential to reduce postharvest decay caused by B. cinerea and P. expansum, when applied directly to the fruit. © 2014.

Mutawila C.,Stellenbosch University | Halleen F.,Agricultural Research Council Infruitec Nietvoorbij | Mostert L.,Stellenbosch University
BioControl | Year: 2015

In the protection of grapevine pruning wounds from trunk pathogen infection, fungicides provide mainly short term protection while biocontrol agents provide mainly long term protection. The integration of fungicide and biological wound protection could provide better wound protection, but is limited by the susceptibility of the biocontrol agents to the fungicides. Stable benzimidazole resistant mutants were generated by gamma irradiation (250 Gy) from three wild-type Trichoderma Pers. isolates (UST1, UST2 and T77) shown to provide wound protection. The wild-type Trichoderma isolates were found to be naturally resistant to thiophanate methyl while mycelial growth was completely inhibited by 2.5 μg ml−1 of benomyl and carbendazim. There was no reduction in biological fitness and in vitro antagonist activity for mutants generated from UST1 and UST2 while the mutant from T77 had reduced fitness and antagonistic activity compared to its wild type. The wild type and the mutant of UST1 were further tested in the field and significantly (P < 0.001) reduced pruning wound infection by Phaeomoniellachlamydospora (W. Gams, Crous, M.J. Wingf. & Mugnai) Crous & W. Gams, when applied alone and in combination with thiophanate methyl and carbendazim, respectively. The combination of the mutant UST1 with carbendazim gave the highest reduction of infection compared to the rest of the treatments when P. chlamydospora was inoculated 24 h after pruning. The Trichoderma transformants generated in this study can be applied in combination with benzimidazole fungicides for a more effective and sustainable wound protection. © 2014, International Organization for Biological Control (IOBC).

Tounekti T.,Gabes University | Joubert E.,Agricultural Research Council Infruitec Nietvoorbij | Joubert E.,Stellenbosch University | Hernandez I.,University of Barcelona | Munne-Bosch S.,University of Barcelona
Critical Reviews in Plant Sciences | Year: 2013

Tea, prepared from the leaves of Camellia species, has one of the highest contents of flavonoids among common food and beverage products. Tea consumption has moved beyond its pleasant flavor and cultural significance since a number of health promoting properties have been ascribed to this widespread beverage (e.g., anticancer, antiobesity and hypotensive effects). The major bioactive compounds in tea are catechins (flavan-3-ols), a group of flavonoids that include, among others, (-)-epicatechin (EC), (-)-epigallocatechin (EGC), (-)-epicatechin-3-gallate (ECG), and (-)-epigallocatechin-3-gallate (EGCG). These compounds are also the precursors of theaflavins and thearubigins, oxidation products responsible for the taste and colour of certain tea types such as black tea. The composition of the tea leaf, and thus tea quality, is influenced by many pre-harvest factors such as the genetic make-up of the plant, region of production, horticultural and harvesting practices, and environmental conditions. Once harvested, processing, brewing, and storage conditions influence the phenolic composition and quality of tea infusions as well. In the present review we aim at outlining our current knowledge about means to increase the catechin content of teas, a cornerstone for improving the health-promoting properties of this beverage. © 2013 Copyright Taylor and Francis Group, LLC.

Beelders T.,Stellenbosch University | Kalili K.M.,Stellenbosch University | Joubert E.,Stellenbosch University | Joubert E.,Agricultural Research Council Infruitec Nietvoorbij | And 2 more authors.
Journal of Separation Science | Year: 2012

Rooibos tea is an unique beverage prepared from unfermented and fermented plant material of the endemic Cape fynbos plant, Aspalathus linearis. The well-known health-promoting benefits of rooibos are partly attributed to its phenolic composition. Detailed investigation of the minor phenolic constituents of rooibos is, however, hampered by the limitations associated with conventional HPLC methods used for its analysis. In this study, the applicability of comprehensive two-dimensional liquid chromatographic methods for the in-depth analysis of rooibos phenolics was investigated. Phenolic compounds were separated according to polarity by hydrophilic interaction chromatography (HILIC) in the first dimension, whilst reversed-phase liquid chromatography (RP-LC) provided separation according to hydrophobicity in the second dimension. Ultraviolet photodiode array and electrospray ionisation mass spectrometry were used to identify phenolic compounds. Comprehensive HILIC × RP-LC demonstrated its applicability for the analysis of a diverse range of phenolic compounds in unfermented and fermented rooibos samples, in which large qualitative differences in the phenolic composition were established. The combination of these orthogonal separations provided a significant improvement in resolution, as exemplified by practical peak capacities in excess of 2000 and 500 for off-line and on-line methods, respectively. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Bester R.,Stellenbosch University | Jooste A.E.C.,Plant Protection Research Institute | Maree H.J.,Stellenbosch University | Maree H.J.,Agricultural Research Council Infruitec Nietvoorbij | Burger J.T.,Stellenbosch University
Virology Journal | Year: 2012

Background: Grapevine leafroll-associated virus 3 (GLRaV-3) is the main contributing agent of leafroll disease worldwide. Four of the six GLRaV-3 variant groups known have been found in South Africa, but their individual contribution to leafroll disease is unknown. In order to study the pathogenesis of leafroll disease, a sensitive and accurate diagnostic assay is required that can detect different variant groups of GLRaV-3. Methods. In this study, a one-step real-time RT-PCR, followed by high-resolution melting (HRM) curve analysis for the simultaneous detection and identification of GLRaV-3 variants of groups I, II, III and VI, was developed. A melting point confidence interval for each variant group was calculated to include at least 90% of all melting points observed. A multiplex RT-PCR protocol was developed to these four variant groups in order to assess the efficacy of the real-time RT-PCR HRM assay. Results: A universal primer set for GLRaV-3 targeting the heat shock protein 70 homologue (Hsp70h) gene of GLRaV-3 was designed that is able to detect GLRaV-3 variant groups I, II, III and VI and differentiate between them with high-resolution melting curve analysis. The real-time RT-PCR HRM and the multiplex RT-PCR were optimized using 121 GLRaV-3 positive samples. Due to a considerable variation in melting profile observed within each GLRaV-3 group, a confidence interval of above 90% was calculated for each variant group, based on the range and distribution of melting points. The intervals of groups I and II could not be distinguished and a 95% joint confidence interval was calculated for simultaneous detection of group I and II variants. An additional primer pair targeting GLRaV-3 ORF1a was developed that can be used in a subsequent real-time RT-PCR HRM to differentiate between variants of groups I and II. Additionally, the multiplex RT-PCR successfully validated 94.64% of the infections detected with the real-time RT-PCR HRM. Conclusion: The real-time RT-PCR HRM provides a sensitive, automated and rapid tool to detect and differentiate different variant groups in order to study the epidemiology of leafroll disease. © 2012 Bester et al.; licensee BioMed Central Ltd.

Myburgh P.A.,Agricultural Research Council Infruitec Nietvoorbij
South African Journal of Plant and Soil | Year: 2015

Estimating soil evaporation (Es) is an important part of modelling vineyard evapotranspiration for irrigation purposes. Furthermore, quantification of possible soil texture and trellis effects is essential. Daily Es from six topsoils packed into lysimeters was measured under grapevines on slanting and vertical trellises, respectively. Following irrigation, cumulative soil evaporation (ΣEs) from the bare, untilled soils over 14-day drying cycles was plotted against cumulative reference evapotranspiration (ΣETo) to determine Es transition from the constant rate stage (Stage 1) to the falling-rate stage (Stage 2). During Stages 1 and 2, rate of Es is determined by atmospheric conditions and soil properties, respectively. Slopes of ΣEs vs square root of ΣETo plots in Stage 2 provided the input constant (β value) for each soil. In Stage 1, ΣEs was almost equal to ΣETo but the ratio varied as grapevine canopies developed. The β values varied between 2.15 ± 0.09 mm0.5 and 4.68 ± 0.14 mm0.5. The β values were best related to clay content (R2 was 0.7861 and 0.5108 for horizontal and vertical canopies, respectively). The vertical trellis seemed to have a windbreak effect that tended to reduce Es compared to the slanting trellis. Therefore, clay content and trellis orientation effects on β need to be considered. © 2015 © Southern African Plant & Soil Sciences Committee.

Myburgh P.A.,Agricultural Research Council Infruitec Nietvoorbij | Howell C.L.,Agricultural Research Council Infruitec Nietvoorbij
South African Journal of Plant and Soil | Year: 2014

A pot experiment was carried out to determine the sodium (Na) absorption ability of halophytic fodder beet (Beta vulgaris L. Brigadier) irrigated with water enriched to Na levels found in winery wastewater. Treatments comprised (1) soil without plants irrigated with untreated water or (2) Na-enriched water, and (3) fodder beet irrigated with untreated water or (4) Na-enriched water. Irrigation with Na-enriched water did not affect fresh or dry matter production of fodder beet compared to irrigation with untreated water. Fodder beet absorbed 38% of the Na applied through the irrigation water compared to soil without plants. Since the bulk of the plant can be harvested for fodder, Na will be removed more effectively compared to crops where roots remain in the soil. Therefore, this halophyte holds promise as an interception crop to reduce Na accumulation where winery wastewater is used for irrigation. © 2014 © Southern African Plant and Soil Sciences Committee.

Mulidzi A.R.,Agricultural Research Council Infruitec Nietvoorbij
Water Science and Technology | Year: 2010

The rationale for using constructed wetlands for treating wastewater is that wetlands are naturally among the most biological active ecosystem on earth. The aim of the study was to determine the impact of shorter retention time on the performance of constructed wetland in terms of Chemical Oxygen Demand (COD) and other elements removal. The application of wastewater with retention time of seven days as well as the evaluation of water quality after treatment at Goudini experimental wetland was carried out throughout the year. The results had shown an overall average COD removal of 60% throughout the year. Results also showed reasonable removal of other elements namely; potassium, pH, nitrogen, electrical conductivity, calcium, sodium, magnesium and boron from the wastewater by constructed wetlands. The results showed low COD removal during July until September after which it improved tremendously. The reason for low COD removal during first three months could be attributed to the fact that there was no gradual increase of wastewater application to the wetlands i.e. from 4,050 litres per day to 8,100 litres per day. The results had showed that constructed wetland as a secondary treatment system is effective in terms of COD and other elements removal from winery and distillery wastewater. COD removal throughout the year was 60% with seven days retention time. When compared with previous studies that showed 80% COD removal within 14 days retention time, therefore the 60% removal is very critical to wine industries as more wastewater will be applied to the system. © IWA Publishing 2010.

Tolmay V.L.,Agricultural Research Council Small Grain Institute | Booyse M.,Agricultural Research Council Infruitec Nietvoorbij
South African Journal of Plant and Soil | Year: 2016

Resistance-breaking biotypes of Diuraphis noxia have been reported in both the USA and South Africa where commercial cultivars with genetic resistance to this pest have been deployed. The need to identify novel Russian wheat aphid (RWA) resistance for deployment against new biotypes of RWA has driven the recent re-evaluation and characterisation of resistance in landraces of bread wheat from germplasm collections worldwide. Twenty-three genotypes already in use in a South African pre-breeding programme were evaluated with the extended spectrum of South African RWA biotypes, while four genotypes not yet tested with South African RWA were screened with RWASA1, RWASA2, RWASA3 and RWASA4 for the first time. Five accessions, namely PI 94355, PI 243781, PI 361836, PI 626580 and the check CItr 2401, were resistant to all four South African RWA biotypes. The previously unused accessions PI 094355 and PI 243781 will be incorporated into the programme. The sixth accession resistant to RWASA4, namely PI 366518, is susceptible to RWASA2 and RWASA3 and may possibly be unique, meriting emphasis in pre-breeding activities. The use of multiple, distinct resistance genes, including those with a moderate resistance reaction, is seen as the most responsible strategy for the stewardship of genetic resistance to RWA in bread wheat. © 2016 Southern African Plant & Soil Sciences Committee

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