ARC Biometry Unit

Stellenbosch, South Africa

ARC Biometry Unit

Stellenbosch, South Africa

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Van der Merwe M.,Tshwane University of Technology | Hoffman L.C.,Stellenbosch University | Jooste P.J.,Tshwane University of Technology | Calitz F.J.,ARC Biometry Unit
Meat Science | Year: 2013

Three game meat production systems used on game ranches in South Africa are reported on. System one is applied in the game export market and conforms to the hygiene requirements of the European Union (EU). System two and three entail game meat available on the local market not subjected to any regulation. System 2 however, implemented basic meat hygiene values.Measurements of pH, temperature, Aerobic Plate Count (APC), E. coli, Salmonella and S. aureus were subjected to a 3. ×. 2 factorial analysis of variance with factors that involve 3 system compliances in 2 classes of game animals in a completely randomised design.The measured bacteriological and quality differences between the three systems do not justify EU standards application on the local market but results indicated a significant compliance. ×. class interaction. © 2013 Elsevier Ltd.

van Zyl S.A.,Stellenbosch University | Brink J.-C.,Stellenbosch University | Calitz F.J.,ARC Biometry Unit | Coertze S.,Stellenbosch University | And 2 more authors.
Crop Protection | Year: 2010

Spray adjuvants have the potential to improve deposition by effecting uniform distribution of the active ingredient on plant surfaces. In order to study whether such a qualitative improvement of spray deposition would lead to improved disease control, a laboratory experiment was conducted on artificially inoculated grapevine (cv. Chardonnay) leaves. Prior to inoculation with Botrytis cinerea conidia in a spore settling tower, leaves were sprayed to pre-runoff with 1 mL of a mixture of fenhexamid, a fluorescent pigment, and one of 15 selected commercial adjuvants to manipulate the deposition quality of a specific quantity of spray. Following an incubation period of 24 h at high relative humidity, leaf discs were plated onto Petri dishes with paraquat-amended water agar and rated for development of B. cinerea from isolated leaf discs 11 d later. Spray deposition on leaves was assessed with a spray assessment protocol using fluorometry, photomicrography and digital image analyses. B. cinerea incidences on the upper and lower surfaces of water-sprayed leaves averaged 90.4% and 95.8%, respectively. Despite full spray cover of leaves, applications with fenhexamid alone did not completely prevent infection and resulted in 34.6% and 40.8% B. cinerea incidences on the upper and lower surfaces of leaves, respectively. Through the addition of certain adjuvants, B. cinerea incidences were significantly reduced (incidences of 2.9-17.1% and 10.0-30.8%, respectively), while some adjuvants did not differ from the fungicide only treatment, even though they might have improved spray deposition. In a histopathology study using epifluorescence microscopy, distinct differences were observed in conidium mortality (20.5% vs. 31.2%), germination (60.4% vs. 51.4%) and germ tube lengths (27.8 μm vs. 19.7 μm) between Hydrosilicote and Solitaire in combination with fenhexamid, even though both adjuvants effected similar quantitative and qualitative spray deposition. The study clearly demonstrated the potential of adjuvants to improve the bio-efficacy of a fungicide directly through improved deposition on grapevine leaf surfaces, although bio-efficacy might be influenced by adjuvant mode of action in some cases. © 2009 Elsevier Ltd. All rights reserved.

van Niekerk J.M.,Stellenbosch University | Calitz F.J.,ARC Biometry Unit | Halleen F.,ARC Infruitec Nietvoorbij | Fourie P.H.,Stellenbosch University | Fourie P.H.,Citrus Research International
European Journal of Plant Pathology | Year: 2010

Trunk disease pathogens of grapevines, viz. Phaeomoniella chlamydospora, Eutypa lata and several species in Botryosphaeriaceae, Phaeoacremonium and Phomopsis are known to infect fresh pruning wounds by means of air-borne inoculum released after rainfall or prolonged periods of high relative humidity. Recent surveys have demonstrated that most or all of these pathogens are present in climatically diverse grape growing regions of South Africa. However, the factors controlling spore dispersal of these pathogens in vineyards were largely unknown. To address this question, spore trapping was done in a Chenin Blanc vineyard in the Stellenbosch area, South Africa, for 14 weeks during the grapevine pruning period from June to mid-September of 2004 and 2005. Hourly recordings of weather data were done by a weather station in the row adjacent to the spore trap. Spores of E. lata and Phomopsis and species in Botryosphaeriaceae were trapped throughout the trapping periods of 2004 and 2005, with higher levels of trapped spores recorded in 2005. The spores of all three pathogens were trapped during or after periods of rainfall and/or high relative humidity. In neither of the 2 years were spores of Pa. chlamydospora or Phaeoacremonium spp. trapped. Results indicated that spore event incidence, as well as the amount of spores released during a spore event of above-mentioned pathogens, were governed by rainfall, relative humidity, temperature and wind speed prior to and during the spore events. © 2010 KNPV.

Spies C.F.J.,Stellenbosch University | Mazzola M.,U.S. Department of Agriculture | Botha W.J.,ARC PPRI | Van Der Rijst M.,ARC Biometry Unit | And 2 more authors.
Fungal Biology | Year: 2011

Pythium vexans fits into the internal transcribed spacer (ITS) clade K sensu Lévesque & De Cock (2004). Within clade K, P. vexans forms a distinct clade containing two enigmatic species, Pythium indigoferae and Pythium cucurbitacearum of which no ex-type strains are available. In South Africa, as well as in other regions of the world, P. vexans isolates are known to be heterogeneous in their ITS sequences and may consist of more than one species. This study aimed to investigate the diversity of South African P. vexans isolates, mainly from grapevines, but also citrus and apple using (i) phylogenetic analyses of the ITS, cytochrome c oxidase (cox) I, cox II, and β-tubulin regions and (ii) seven biometric oogonial parameters. Each of the phylogenies clustered P. vexans isolates into a single well-supported clade, distinct from other clade K species. The β-tubulin region was phylogenetically uninformative regarding the P. vexans group. The ITS phylogeny and combined cox I and II phylogenies, although each revealing several P. vexans subclades, were incongruent. One of the most striking incongruences was the presence of one cox subclade that contained two distinct ITS subclades (Ib and IV). Three groups (A-C) were subjectively identified among South African P. vexans isolates using (i) phylogenetic clades (ITS and cox), (ii) univariate analysis of oogonial diameters, and (iii) multivariate analyses of biometric oogonial parameters. Group A is considered to be P. vexans s. str. since it contained the P. vexans CBS reference strain from Van der Plaats-Niterink (1981). This group had significantly smaller oogonial diameters than group B and C isolates. Group B contained the isolates from ITS subclades Ib and IV, which formed a single cox subclade. The ITS subclade IV isolates were all sexually sterile or produced mainly abortive oospores, as opposed to the sexually fertile subclade Ib isolates, and may thus represent a distinct assemblage within group B. Although ITS subclade Ib included the P. indigoferae ex-type sequence, this group was considered to be P. vexans since South African isolates in this clade produced globose sporangia. Group C contained four apple isolates that were related to, but distinct from P. cucurbitacearum. Although P. vexans groups A-C might be distinct species, they are not described here as such due to (i) these groups only representing some of the known diversity in P. vexans, (ii) conflicting gene tree phylogenies preventing phylogenetic species identification, and (iii) sexually sterile isolates preventing the broad application of biometrical data. © 2010 The British Mycological Society.

van Zyl S.A.,Stellenbosch University | Brink J.-C.,Stellenbosch University | Calitz F.J.,ARC Biometry Unit | Fourie P.H.,Stellenbosch University | Fourie P.H.,Citrus Research International
Crop Protection | Year: 2010

Adequate spray deposition on susceptible grapevine tissue is an essential requirement for effective chemical control of economically important diseases, such as grey mould, powdery mildew and downy mildew. The objective of this study was to evaluate the potential of some agricultural adjuvants to improve foliar spray deposition. Deposition quantity and quality was assessed by means of a spray assessment protocol using fluorometry, photomicrography and digital image analyses. The visual droplet rating technique developed by G Furness, Australia, was also included in initial assessments. Both assessment protocols showed that spray deposition quantity increased with increasing spray volume applications of 27lha-1 to 581lha-1 with a motorised backpack mistblower, but decreased at 698lha-1, possibly due to run-off. Addition of selected spray adjuvants at 526lha-1 volume demonstrated improved deposition quantity and quality. Agral 90 (ethoxylated alkylphenol), BB5 (acidifier), Nu-film-P (terpene oil), and Solitaire (silicone/plant oil) significantly improved deposition on upper and lower leaf surfaces compared with the fenhexamid-only and water sprayed control. Break-thru S240 (organosilicone) and Villa 51 (alkylpolyethylene glycol ether) did not improve deposition quantity, although remarkably better deposition quality was obtained. An adjuvant concentration effect (within the registered concentration range) was evident at spray volumes of 502lha-1, especially those retained on the upper leaf surfaces. Agral 90 and Nu-film-P effected significant improvement of spray deposition at the higher concentrations (18ml and 50mlhl-1, respectively), but not at the lower concentrations (6ml and 20mlhl-1, respectively). Solitaire improved deposition at the lower concentration tested (50mlhl-1), whereas reduced deposition at the higher concentration (100ml per hl-1) was attributed to excessive spray run-off. No significant improvement of spray deposition was observed for both concentrations tested with Villa 51 (50 and 100mlhl-1). Spray mixtures with adjuvants Agral 90 and Solitaire yielded similar deposition values at 500lha-1 compared with the fenhexamid-only control at 720lha-1, but reduced deposition at the higher spray volume, possibly due to spray run-off. This study clearly demonstrated the potential of adjuvants to improve deposition quantity and quality, but highlights the necessity to match adjuvant concentrations and application volumes on the spray target to achieve maximum spray deposition. © 2010 Elsevier Ltd.

Van Heerden S.M.,ARC Animal Production Institute | Smith M.F.,ARC Biometry Unit
Food Chemistry | Year: 2013

The shoulder, loin and leg from P-class pork carcasses were used to determine the nutrient composition of both raw and cooked cuts. Significantly lower fat content were observed in the current study for the leg (5.21 g/100 g) and loin (6.99 g/100 g) compared to the shoulder cut (10.32 g/100 g). The overall percentage fat for all three cuts was less than 10% which is recommended by the South African Heart Mark. The cooked loin cut contained the most protein (27.50 g/100 g) of the three cooked cuts. When compared to other meat products (beef, mutton and chicken) it is clear that pork is a good source of B vitamins, especially vitamin B3. The cooked loin cut contained the least vitamin B1 (0.22 mg/100 g), B2 (0.02 mg/100 g) but the most vitamin B3 (7.09 mg/100 g), of the three cooked cuts. The 100 g cooked shoulder, loin and leg cuts provide on average 40.11% protein, 5.19% magnesium, 3.37% calcium, 24.29% phosphorus, 18.22% zinc, 22.33% iron and 22.50% vitamin B1, 2.57% vitamin B2 and 42.6% vitamin B 3 of Recommended Daily Allowances for males, age 25-50. Energy from a 100 g portion provides 5.81% of the Recommended Daily Allowances. To conclude, the pork cuts are undoubtedly a good source of nutrients that is required for good health because it is high in protein, have a low fat content and are a nutrient-packed choice for the family and compares favourably with the fat, energy, and cholesterol content of many other meats and poultry. © 2013 Elsevier Ltd. All rights reserved.

Minnaar P.P.,ARC Infruitec Nietvoorbij | Booyse M.,ARC Biometry Unit
South African Journal of Enology and Viticulture | Year: 2011

Various factors affect the polyphenol compound concentrations of red grapes. These include cultivar, vineyard location, viticultural practices, microclimate, soil type and winemaking processes. Polyphenol compound concentrations of young and market-ready Cabernet Sauvignon, Pinotage and Shiraz wines were examined for the purpose of discrimination between grape cultivars. Thirty-five individual polyphenol compounds were quantified using a HPLC-DAD method. Stepwise discriminant analysis (SDA) was used to select a subset of discriminatory variables. In addition, data was grouped and investigated by canonical discriminant analysis, which showed that polyphenol concentrations can be used to discriminate among grape cultivars, young wines and market-ready wines. Flavonol, flavanol and anthocyanin patterns were used as a basis for differentiation of young wines, while flavanols and phenolic acids were used for differentiation of market-ready wines. Discriminant analysis performed at 95% significance level revealed a 100% categorisation of market-ready and young wines in terms of cultivar and 77.85% categorisation of a combination of market-ready and young wines in terms of grape cultivar. This illustrates the validity of polyphenols for studies pertaining to grape cultivar discrimination.

North M.S.,ARC Infruitec Nietvoorbij | De Kock K.,ARC Infruitec Nietvoorbij | Booyse M.,ARC Biometry Unit
Acta Horticulturae | Year: 2014

Rest Breaking Agents (RBA) are used to reduce the negative effects of insufficient winter chilling. Their effectiveness depends on application date, concentration, chemistry and cultivar. In a four year study, RBA were applied five to six times between early August and late September to single-tree plots within mature commercial Royal Gala (RG) and Granny Smith (GS) apple orchards on the same farm. The results from the final year are presented here. Either Dormex®/oil (0.5%/4% v/v), Symphony® (16% N), Oil (5%), Oil/Oil (5%/5% one week later), GAN/Partner® (5%/2%) or Oil/Urea (5%/5% m/v) were applied using motorized knapsack sprayers. Control trees were left untreated. Bud break (BB) on one-year-old pre-marked shoots and fruit/tree and kg/tree were recorded. In GS, Oil and Oil/Urea on the second date (25/8/11); Symphony®, Oil/Oil, GAN/Partner® and Oil/Urea on the third date (7/9/11); DM/Oil, Symphony and GAN/Partner® on the fourth date (21/9/11) and GAN/Partner® on the fifth date (27/9/11) improved BB relative to the control. No RBA affected yield. Trees receiving the first application (10/8/11) had more fruit/tree than the control. In RG, Symphony®, Oil/Oil and Oil/Urea treatments had higher BB than the control. Higher BB occurred after the third application (7/9/11) than after the first (10/8/11), fourth and fifth applications. In the first harvest, DM/Oil and Oil/Oil treatment trees had higher kg/tree, and the Oil/Urea treatment lower kg/tree than the control. Neither RBA nor application date had any effect on total fruit/tree, kg/tree or fruit size. Although some treatments promoted BB, the final yield of either cultivar was not affected.

Laurie S.M.,Agricultural Research Council ARC Roodeplaat Vegetable and Ornamental Plant Institute | Booyse M.,ARC Biometry Unit | Labuschagne M.T.,University of the Free State | Greyling M.M.,Agricultural Research Council ARC Roodeplaat Vegetable and Ornamental Plant Institute
Crop Science | Year: 2015

Vitamin A deficiency is a serious health problem in South Africa, as in several parts of the world. One strategy to combat micronutrient deficiency is through biofortification, particularly through orange-fleshed sweetpotato [Ipomoea batatas (L.) Lam]. Previously, a shortage existed in South Africa of orange-fleshed genotypes with a combination of high dry mass, good yield, and good taste. Local cream-fleshed parents and orange-fleshed US introductions were used in the local polycross program. This study aimed at testing the agronomic performance, stability, and genetic diversity of newly developed orange-fleshed genotypes. Twelve entries, nine with orange flesh color, were evaluated at four sites for two seasons in multienvironment trials and the data was subjected to ANOVA and genotype plus genotype-by-environment interaction (GGE) biplot analysis. Simple-sequence repeat (SSR) analysis of the 12 entries was done followed by hierarchical clustering. Two of the orange-fleshed cultivars were recommended for production and plant breeders’ rights were registered for these. Cultivar Impilo produced stable, high root yield similar to the commercial control cultivar Beauregard; while the elite breeding line Purple Sunset (2001_5_2) had high yield and specific adaptability. Both displayed average dry mass and acceptable taste. The genetic analysis indicated relatedness of most new genotypes with the cream-fleshed parents used in the polycross program. The improved cultivars offer considerable yield advantage above US introductions previously recommended for combating vitamin A deficiency. © Crop Science Society of America.

van Heerden S.M.,ARC Animal Production Institute | Morey L.,ARC Biometry Unit
Journal of Food Measurement and Characterization | Year: 2014

The aim of this study was to determine a selected group of nutrients in raw and cooked C-age, fat code 2, bovine offal and to evaluate it as a potential source of nutrients such as protein and iron. Samples of the different raw and cooked C-age, fat code 2 bovine offal parts were analysed by accredited laboratories. Cooking affected mainly the nutrients such as moisture, protein, fat, ash and energy as well as the micronutrient values, which were higher in the cooked offal cuts. Some cuts of offal (heart, lungs and spleen) are as lean as or leaner than chicken meat. The biggest difference could be attributed to the difference in fat content between the cuts, for example, the tongue is very high in fat with 23.30 g/100 g and therefore has the highest kJ (1,157 kJ) content of the six cuts of offal. The spleen had the highest iron content of 36.6 mg/100 g. Significantly lower fat contents were observed in the lungs (2.53 g/100 g), heart (6.7 g/100 g) and the spleen (3.20 g/100 g) cuts when compare to the values in the 1999 version of the South African Medical Research Council's Food Composition Tables. The heart, intestine and spleen are also an important source of iron and compare favourable to beef. The heart also contained the highest zinc content of all the cuts. Offal containing primary food components which have high potential in human nutrition such as high protein content and can therefore is recommended as a good low cost nutritious product. © 2014 Springer Science+Business Media New York.

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