Booi S.,Agricultural Research Council ARC Infruitec Nietvoorbij |
Malan A.P.,Stellenbosch University
Acta Horticulturae | Year: 2013
The future banning of soil fumigants by 2015 is likely to have a negative impact on the South African stone fruit industry. The industry is currently dependent on a few high-chill imported commercial rootstocks that, in many cases, are not adapted to local soil and climatic conditions. Plant-parasitic nematodes are a severe problem worldwide, with serious economic implications for the fruit industry. Therefore, the continuous improvement and the development of crops with increased resistance or tolerance to pests and diseases, as well as to harsh environmental conditions is of importance. In South Africa the most important plant-parasitic nematodes on stone fruit rootstocks are Criconemoides xenoplax (ring nematode) and Meloidogyne javanica (root-knot nematode). Agricultural Research Council (ARC)-bred stone fruit hybrids were screened for nematode resistance or tolerance under controlled conditions during 2009/10 and 2010/11 at the ARC Infruitec-Nietvoorbij facility at Bien Donne Experimental Farm, Simondium, Western Cape. Screening was done on rooted cuttings in black nursery bags, in a complete randomised block design housed in a greenhouse to evaluate the effect of the two nematode species. Inoculum of C. xenoplax was produced using the peach cultivar 'Atlas' as host and for M. javanica the tomato cultivar 'Moneymaker'. A concentration of 2,000 J2 C. xenoplax in 100 ml soil, and 2,000 eggs M. javanica in water, was added to each plant. After a period of six months, C. xenoplax were extracted from the soil, using a sugar flotation technique and the number of nematodes per 250 g of soil determined. For M. javanica, the soil was washed from the roots and the roots were scored according to a gall index on a scale from 0 to 5. To date, the stone fruit rootstock breeding programme has bred very promising stone fruit rootstocks that are suitable for South African commercial growers and emerging farmers.
van der Merwe H.,Stellenbosch University |
Nieuwoudt H.,Stellenbosch University |
de Beer D.,Agricultural Research Council ARC Infruitec Nietvoorbij |
du Toit W.J.,Stellenbosch University
South African Journal of Enology and Viticulture | Year: 2012
Colour and phenolic content of red grapes are two of the most important constituents required to produce a quality red wine. In the Robertson grape growing area, difficulty is sometimes experienced with colour development of grapes. This is especially linked to location and most probably greatly influenced by season. Forty four vineyard blocks of the cultivars Pinotage, Merlot, Cabernet Sauvignon and Shiraz, were studied over 3 seasons primarily to focus on colour and phenolic content, but secondly on total soluble solids, titratable acidity and pH of the grapes. High performance liquid chromatography and spectrophotometric methods were used to determine various colour and phenolic parameters present at harvest. This data was used to indicate how colour and phenolic constitution of a part of the Robertson grape growing area was distributed in relation to various factors, such as cultivar and season. GPS points were used to map data for the blocks visually. Results showed variable colour and phenolic content for these grapes based on blocks and phenolic compounds investigated. Shiraz displayed a wider distribution of certain phenolic compounds over the three seasons than the other 3 cultivars. Seasonality had a great influence on these results, with outlying blocks being identified.
Joubert E.,Agricultural Research Council ARC Infruitec Nietvoorbij |
Viljoen M.,Matieland |
De Beer D.,Agricultural Research Council ARC Infruitec Nietvoorbij |
Malherbe C.J.,Agricultural Research Council ARC Infruitec Nietvoorbij |
And 2 more authors.
Journal of Agricultural and Food Chemistry | Year: 2010
Heat-induced changes in aspalathin, iso-orientin, and orientin content of ready-to-drink (RTD) green rooibos iced tea formulations were investigated. An organic-solvent-based aspalathin-enriched extract prepared from green rooibos was used "as-is" or encapsulated with ascorbic acid in a water-soluble nanomicelle-based carrier system. The common iced tea ingredients, ascorbic acid, and/or citric acid were added to the iced tea containing green rooibos extract. Only citric acid was added to the iced tea containing the nanomicelles. Heat treatments consisted of pasteurization (93 °C/5 min and 93 °C/30 min), normaltemperature sterilization (NTS; 121 °C/15 min), and high-temperature sterilization (HTS; 135 °C/4 min). Pasteurization had little or no effect on the flavonoid content. NTS and HTS induced significant losses in the flavonoids. The addition of citric and ascorbic acids improved the stability of the flavonoids, but encapsulation of green rooibos extract with ascorbic acid in nanomicelles did not offer additional stability. The only benefit of using the water-soluble nanomicelles was the improved clarity of the RTD product. Isoorientin and orientin contents were substantially less affected than aspalathin by the heat treatments, partially because of conversion of aspalathin to these flavones, which countered losses. 5-Hydroxymethylfurfural (HMF), a known dehydration product of hexoses under mild acidic conditions and also a degradation product of ascorbic acid, was observed in formulations containing citric and/or ascorbic acids. ©2010 American Chemical Society.
Allsopp E.,Agricultural Research Council ARC Infruitec Nietvoorbij |
Allsopp E.,Stellenbosch University |
Prinsloo G.J.,ARC Small Grain Institute |
Smart L.E.,Rothamsted Research |
Dewhirst S.Y.,Rothamsted Research
Arthropod-Plant Interactions | Year: 2014
A bioassay was developed to determine whether treatment with essential oils thymol, methyl salicylate and carvacrol can reduce the oviposition rate of western flower thrips (wft), Frankliniella occidentalis, on plum blossoms. Individual field-collected wft females were confined on single blossoms treated with three concentrations of essential oils applied in different suspensions: an aqueous 0.05 % Triton X-100 plus ethanol solution [ethanol/water/Triton (EWT)], an EWT plus Citrex® medium mineral oil and an aqueous 0.05 % Triton X-100 solution (water/Triton) plus Citrex®. The number of eggs laid per female over 24 h was compared to oviposition on untreated blossoms and those treated with control suspensions. A 10 % suspension of thymol significantly reduced oviposition rate by 85 % compared with blossoms treated with control suspension and untreated. Methyl salicylate concentrations of 10 and 1 % significantly reduced oviposition rate by 84 and 88 %, respectively, compared with the control suspension and, 89 and 85 %, respectively compared with the untreated. Carvacrol concentrations of 5, 1 and 0.1 % significantly reduced oviposition rate compared with untreated blossoms (84, 53 and 57 %), whilst the 5 % was also significantly different to the control suspension (69 % reduction). Suspension type had no significant effect on mean oviposition rate. We have shown that these essential oils are effective in reducing wft egg-laying when applied to fragrant flowers and have potential for inclusion in pest management strategies for this pest on plums. Further research is required to develop stable suspensions that provide an even deposit, more sustained release and that can reduce the phytotoxicity observed with the higher concentrations. © 2014, Springer Science+Business Media Dordrecht.
van Dyk M.M.,University of the Western Cape |
van Dyk M.M.,University of Pretoria |
Soeker M.K.,University of the Western Cape |
Labuschagne I.F.,Agricultural Research Council ARC Infruitec Nietvoorbij |
And 2 more authors.
Tree Genetics and Genomes | Year: 2010
In the Western Cape region of South Africa, dormancy release and the onset of growth does not occur normally in apple (Malus x domestica Borkh.) trees during spring due to the mild winter conditions experienced and fluctuations in temperatures experienced during and between winters. In this region, the application of chemicals to induce the release of dormancy forms part of standard orchard management. Increasing awareness of the environmental impact of chemical sprays and global warming has led to the demand for new apple cultivars better adapted to local climatic conditions. We report the construction of framework genetic maps in two F1 crosses using the low chilling cultivar 'Anna' as common male parent and the higher chill requiring cultivars 'Golden Delicious' and 'Sharpe's Early' as female parents. The maps were constructed using 320 simple sequence repeats, including 116 new markers developed from expressed sequence tags. These maps were used to identify quantitative trait loci (QTL) for time of initial vegetative budbreak (IVB), a dormancy related characteristic. Time of IVB was assessed four times over a 6-year period in 'Golden Delicious' x 'Anna' seedlings kept in seedling bags under shade in the nursery. The trait was assessed for 3 years on adult full-sib trees derived from a cross between 'Sharpe's Early' and 'Anna' as well as for 3 years on replicates of these seedlings obtained by clonal propagation onto rootstocks. A single major QTL for time of IVB was identified on linkage group (LG) 9. This QTL remained consistent in different genetic backgrounds and at different developmental stages. The QTL may co-localize with a QTL for leaf break identified on LG 3 by Conner et al. (1998), a LG that was, after the implementation of transferable microsatellite markers, shown to be homologous to the LG now known to be LG 9 (Kenis and Keulemans 2004). These results contribute towards a better understanding regarding the genetic control of IVB in apple and will also be used to elucidate the genetic basis of other dormancy related traits such as time of initial reproductive budbreak and number of vegetative and reproductive budbreak. © 2010 Springer-Verlag.
Booi S.,Agricultural Research Council ARC Infruitec Nietvoorbij
Acta Horticulturae | Year: 2014
Global warming is causing climatic changes that will pose significant difficulties to crop growth in many parts of the world. The South African stone-fruit industry is currently dependent on a few high-chill imported commercial rootstocks that in many cases are not adapted to local soil and climatic conditions. There is a need therefore to continue to improve stone-fruit rootstocks with increased tolerance to harsh environmental conditions such as poor drainage. The South African Agricultural Research Council (ARC) has a breeding and evaluation programme to address such problems. The main objectives of the programme are to breed low-chill stone-fruit rootstocks (peaches, plums, nectarines, apricots and interspecies hybrids) with special emphasis on resistance and/or tolerance to nematodes (root-knot and ring), drought, waterlogging, high pH soils and lime induced iron chlorosis. This report focuses on tolerance to waterlogging. Twelve ARC-bred stone-fruit rootstock hybrids were screened for waterlogging tolerance under controlled glasshouse conditions during 2009/10, 2010/11 and 2011/12 at the ARC Infruitec-Nietvoorbij facility at Bien Donné Experimental Farm, Simondium, Western Cape. Four hybrids were tolerant under these conditions and were promoted to Phase 2 for determination of rooting ability and grafting compatibility under nursery conditions. Two hybrids from the four promoted were included in a statistically designed orchard trial established in 2011 for evaluating production potential under field conditions. The stone-fruit rootstock breeding programme is thus continuing to breed very promising stone-fruit rootstocks suitable for South African commercial growers and emerging farmers.
PubMed | Agricultural Research Council ARC Infruitec Nietvoorbij
Type: Evaluation Studies | Journal: Journal of agricultural and food chemistry | Year: 2010
The effect of various pre-drying treatments and storage temperatures on the color (L*, a*, b*, chroma, and hue angle) and phenolic composition of green Cyclopia subternata was investigated. Pre-drying treatments, which included comminution+drying (T2), steaming (ca. 90-93 degrees C/60 s)+comminution + drying (T3), and comminution+steaming+drying (T4), had a detrimental effect (p<0.05) on the color parameters relative to the control (T1) (drying of intact leaves). All drying took place at 40 degrees C and 30% relative humidity (RH). Of the pre-drying treatments (T2, T3, and T4), the best retention of the green leaf color was observed for T3 (p<0.05). T2 reduced the SS and TP contents of the leaves (p<0.05) as well as the content of individual phenolic compounds, including mangiferin, isomangiferin, and eriocitrin. Scolymoside did not follow the same trend as the other compounds, with the intact leaves having the lowest content. It is postulated that oxidation of eriocitrin (eriodictyol-7-O-rutinoside) to scolymoside (luteolin-7-O-rutinoside) occurred with comminution and steaming. The phenolic composition of samples, subjected to T1 and T3 and a 6 month storage period at 0 and 30 degrees C, remained stable. Storage at 30 degrees C resulted in detrimental color changes, leading to the loss of the green leaf color irrespective of the pre-drying treatment.