Agricultural Research Council Biometry Unit

Pretoria, South Africa

Agricultural Research Council Biometry Unit

Pretoria, South Africa
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Laurie S.M.,Agricultural Research Council Roodeplaat Vegetable and Ornamental Plant Institute ARC Roodeplaat VOPI | Faber M.,Nutritional Intervention Research Unit | Calitz F.J.,Agricultural Research Council Biometry Unit | Moelich E.I.,Stellenbosch University | And 2 more authors.
Journal of the Science of Food and Agriculture | Year: 2013

Background: As eating quality is important for adoption of new varieties, nine orange-fleshed and three cream-fleshed sweet potato varieties were assessed for sensory characteristics, dry mass and free sugar content, instrumental texture and colour and consumer acceptability (n= 216) in a peri-urban South African setting. Results: Cream-fleshed varieties were higher in yellow-green colour and sweet potato-like flavour and lower in graininess. Orange-fleshed varieties were higher in pumpkin-like flavour, orange colour, discolouration and sucrose content. Partial least squares regression analysis showed that the most accepted varieties (Impilo, Excel, Resisto, 2001_5_2, Serolane, W-119 and Monate) were associated with sweet flavour, dry mass and maltose content, while the least accepted varieties (Beauregard, Khano and 1999_1_7) were associated with wateriness. Pearson correlation analysis highlighted correlations of sensory attributes yellow and orange with instrumental colour measurements (colour a* and colour b*), instrumental firmness with sensory firmness, dry mass with sensory wateriness, and maltose content with sensory sweet and sweet potato-like flavour. The varieties were clustered into three groups. Consumer acceptability for eating quality correlated with maltose content, dry mass and sweet flavour. Conclusion: Chemical and instrumental measurements were identified to evaluate key attributes and will be useful in the intermediate phases of sweet potato varietal development. © 2012 Society of Chemical Industry.


Lamprecht S.C.,Agricultural Research Council Plant Protection Research Institute | Tewoldemedhin Y.T.,Agricultural Research Council Plant Protection Research Institute | Hardy M.,Private Bag X1 | Calitz F.J.,Agricultural Research Council Biometry Unit | Mazzola M.,Tree Fruit Research Laboratory
European Journal of Plant Pathology | Year: 2011

Rhizoctonia spp. anastomosis groups (AGs) associated with canola and lupin in the southern and western production areas of the Western Cape province of South Africa were recovered during the 2006 and 2007 growing seasons and identified using sequence analyses of the rDNA internal transcribed spacer regions. The effect of crop rotation systems and tillage practices on the recovery of Rhizoctonia spp. was evaluated at Tygerhoek (southern Cape, Riviersonderend) and Langgewens (western Cape, Moorreesburg) experimental farms. Isolations were conducted from canola planted after barley, medic/clover mixture and wheat, and lupin planted after barley and wheat, with sampling at the seedling, mid-season and seedpod growth stages. In the 2006 study, 93. 5% of the Rhizoctonia isolates recovered were binucleate and 6. 5% multinucleate; in 2007, 72. 8% were binucleate and 27. 2% were multinucleate. The most abundant AGs within the population recovered included A, Bo, I and K, among binucleate isolates and 2-1, 2-2 and 11 among multinucleate isolates. Crop rotation sequence, tillage and plant growth stage at sampling all affected the incidence of recovery of Rhizoctonia, but certain effects were site-specific. The binucleate group was more frequently isolated from lupin and the multinucleate group from canola. AG-2-1 was only isolated from canola and AG-11 only from lupin. This study showed that important Rhizoctonia AGs such as AG-2-1, 2-2 and 11 occur in both the southern and the western production areas of the Western Cape province and that crop rotation consistently influences the incidence and composition of the Rhizoctonia community recovered from the cropping system. © 2011 KNPV.


Merwe M.,Tshwane University of Technology | Jooste P.J.,Tshwane University of Technology | Hoffman L.C.,Stellenbosch University | Calitz F.J.,Agricultural Research Council Biometry Unit
Journal of the South African Veterinary Association | Year: 2013

A study was conducted to compare the excision sampling technique used by the export market and the sampling technique preferred by European countries, namely the biotrace cattle and swine test. The measuring unit for the excision sampling was grams (g) and square centimetres (cm2) for the swabbing technique. The two techniques were compared after a pilot test was conducted on spiked approved beef carcasses (n = 12) that statistically proved the two measuring units correlated. The two sampling techniques were conducted on the same game carcasses (n = 13) and analyses performed for aerobic plate count (APC), Escherichia coli and Staphylococcus aureus, for both techniques. A more representative result was obtained by swabbing and no damage was caused to the carcass. Conversely, the excision technique yielded fewer organisms and caused minor damage to the carcass. The recovery ratio from the sampling technique improved 5.4 times for APC, 108.0 times for E. coli and 3.4 times for S. aureus over the results obtained from the excision technique. It was concluded that the sampling methods of excision and swabbing can be used to obtain bacterial profiles from both export and local carcasses and could be used to indicate whether game carcasses intended for the local market are possibly on par with game carcasses intended for the export market and therefore safe for human consumption. © 2013. The Authors. Licensee: AOSIS OpenJournals. This work is licensed under the Creative Commons Attribution License.


Bahramisharif A.,Stellenbosch University | Lamprecht S.C.,Agricultural Research Council Plant Protection Research Institute | Calitz F.,Agricultural Research Council Biometry Unit | McLeod A.,Stellenbosch University
Plant Disease | Year: 2013

Pathogenic oomycetes, including Phytophthora cinnamomi and several Pythium spp. (Pythium irregulare, P. mamillatum, P. myriotylum, and P. pyrilobum), cause serious damping-off problems in rooibos (Aspalathus linearis) nurseries. The management of these pathogens in organic nurseries is problematic, because phenylamide fungicides may not be used. Compost, or compost in combination with Pythium taxa that are nonpathogenic to rooibos (P. acanthicum, P. cederbergense, and Pythium RB II), were investigated as alternative management options. Compost was able to suppress damping-off caused by several oomycete isolates but there was within- and between-species variation among the 30 evaluated isolates. This phenomenon was observed using two compost batches (A and B) sourced from independent suppliers. Compost B significantly reduced damping-off caused by 60% of the isolates, whereas compost A controlled only 37% of the isolates. The pathogens that were more readily controlled by both composts included P. mamillatum and P. pyrilobum, whereas the composts were ineffective at suppressing damping-off caused by >62% of P. irregulare and >50% of P. myriotylum isolates. Based on the evaluation of one Phytophthora cinnamomi isolate, this pathogen may also be controlled by compost. Neither of the composts as a stand-alone treatment could suppress damping-off caused by a combination of pathogenic species (P. cinnamomi, Pythium irregulare, P. mamillatum, P. myriotylum, and P. pyrilobum). However, damping-off was significantly reduced when nonpathogenic Pythium taxa (P. acanthicum, P. cederbergense, and Pythium RB II) were combined with the composts. Similarly, dampingoff caused by a P. irregulare isolate that was not suppressed by either of the composts alone was significantly suppressed when the two composts were inoculated with the nonpathogenic Pythium taxa. © 2013 The American Phytopathological Society.


Joubert M.E.,Vine and Wine Research Institute of the Agricultural Research Council | Wooldridge J.,Vine and Wine Research Institute of the Agricultural Research Council | Booyse M.,Agricultural Research Council Biometry Unit
Journal of Plant Nutrition | Year: 2010

A survey of plantation-grown Cyclopia subternata showed that average concentrations of nitrogen, phosphorus, potassium, calcium and magnesium in the new top growth of mature seedlings and cuttings were 1.59, 0.09, 0.62, 0.32, and 0.17%, respectively. Respective removal rates of these elements at each harvest averaged 13.1, 0.7, 5.1, 2.6, and 1.4 g plant-1. These quantities were equivalent to. 28% to 45% of the total element in the plant. Concentrations in the top growth of sodium, manganese, iron, copper, zinc and boron averaged, respectively, 1459, 34, 143, 7, 9, and 30 mg kg-1. Old top growth dry mass and root dry mass increased with time. Peak new top growth yields from C. subternata plants derived from seedlings and cuttings differed by only 2.2%. At peak production, new growth constituted 15% of total seedling dry mass and 21% of total cutting dry mass. © Taylor & Francis Group.


Joubert M.E.,Vine and Wine Research Institute of the Agricultural Research Council | Wooldridge J.,Vine and Wine Research Institute of the Agricultural Research Council | Booyse M.,Agricultural Research Council Biometry Unit
Journal of Plant Nutrition | Year: 2010

Results from a five year survey of honeybush (Cyclopia genistoides) in the Cape Floral Kingdom, South Africa, showed that concentrations of nitrogen, phosphorus, potassium, calcium and magnesium in the top growth of mature plants grown from seedlings were 1.29, 0.05, 0.53, 0.22 and 0.09%, respectively. Removal rates at each harvest were 8.23, 0.32, 3.38, 1.40 and 0.57 g of the respective elements per plant. These quantities were equivalent to 48% to 61% of the total mass of each element in the plant. Concentrations in the top growth of sodium, manganese, iron, copper, zinc and boron were, respectively, 1423, 16, 172, 5, 12 and 23 mg kg-1. Seedlings of C. genistoides reached their peak mass around five years after planting, and attained higher dry masses in plantations than in the open veld. Mature, plantation-grown C. genistoides plants yielded around 638 g of top growth dry mass per plant at each harvest.© Taylor & Francis Group, LLC.


Wooldridge J.,Agricultural Research Council Infruitec Nietvoorbij | Joubert M.E.,Agricultural Research Council Infruitec Nietvoorbij | Booyse M.,Agricultural Research Council Biometry Unit
South African Journal of Plant and Soil | Year: 2012

Cyclopia (honeybush), a new and largely unstudied South African horticultural crop, was investigated by carrying out a reconnaissance-level survey of C. genistoides (Cg) populations. Four-year average total dry mass (DM) in plantation-grown Cg cuttings and seedlings, and wild (veld) plants were, respectively, 981, 1 261 and 269 g plant-1. Top growth, thick roots (≥5 mm diameter) and thin roots (<5 mm diameter) constituted 39%, 41% and 20% of total DM in the cuttings, 40%, 43% and 17% in the seedlings, and 51%, 36% and 13% in the wild plants. Total root starch content averaged 13 815 mg (cuttings), 26 771 mg (seedlings) and 5 085 mg (wild plants). Of this starch, 74-80% was located in the thick roots. Thick root:thin root starch content ratios averaged 1.95:1 in the plantations and 3.89:1 in the wild plants, whereas shoot DM:total root DM ratios averaged 0.66:1 in the plantations and 1.03:1 in the wild plants. Starch contents and concentrations were higher between January and March than May to July. To optimise yields and starch contents, Cg should be harvested in autumn rather than summer. Top growth yields per plant in Cg plantations, notably seedlings, exceed those from wild Cg plants. Copyright © Combined Congress Continuing Committee.


Laurie S.M.,Agricultural Research Council ARC Roodeplaat Vegetable and Ornamental Plant Institute | Booyse M.,Agricultural Research Council Biometry Unit
Euphytica | Year: 2015

Sweetpotato is a good source of energy, easy-to-grow and hardy and thus useful in contributing to food security. The current study aimed at identification of the best sweetpotato varieties for multiple desirable traits such as good yield, adaptability (including vine vigor) and tastiness (high dry mass content; taste). Ten South African sweetpotato varieties were evaluated during the period 2002/3–2007/8 at six locations each over two seasons. The sites regression model (SREG) of the genotype plus genotype by environment interaction (GGE) biplot analysis was performed with GenStat to determine stability and adaptability of the varieties. Subsequently, multiple trait selection was performed by using the ranking from Elston index selection. To enable inclusion of varietal stability in multiple trait selection, a stability value was calculated. High yielding varieties included Blesbok, Monate, Ndou and Letlhabula, of which Monate and Letlhabula had stable performance. The advantage, particularly for resource-poor farmers, of a specifically adapted, responsive variety such as Ndou, is the ability to respond to changes in the environment. Based on multiple trait selection varieties Ndou and Monate were recommended for production. The results present an innovative use of Elston index selection, including a stability value, in combination with GGE SREG for recommending varieties with multiple desirable traits. The recommended varieties are of significance for future use to improve food security. © 2015, Springer Science+Business Media Dordrecht.


Lamprecht S.C.,Agricultural Research Council Plant Protection Research Institute | Tewoldemedhin Y.T.,Agricultural Research Council Plant Protection Research Institute | Botha W.J.,Agricultural Research Council Plant Protection Research Institute | Calitz F.J.,Agricultural Research Council Biometry Unit
Plant Disease | Year: 2011

Thirty-three isolates of the Fusarium graminearum species complex obtained from diseased maize (Zea mays) crowns and roots in the Winterton district, KwaZulu-Natal province of South Africa were identified to species level. Their pathogenicity and virulence to maize 'PHI 32D96B' seedlings were determined under glasshouse conditions, with seedling survival and growth and crown and root rot as criteria. Phylogenetic analyses using the 3-O-acetyltransferase (Tri101) gene region sequences revealed the presence of F. boothii (2 isolates), F. graminearum sensu stricto (26 isolates), and F. meridionale (5 isolates) in the F. graminearum species complex associated with diseased maize crowns and roots. Pathogenicity results showed that F. boothii was the most and F. meridionale the least virulent of the three species. F. boothii and F. graminearum sensu stricto significantly reduced survival of seedlings and all three species caused significant reduction in growth and significantly more crown and root rot than the control (uninoculated). This is the first report of F. boothii, F. graminearum sensu stricto, and F. meridionale associated with diseased maize crowns and roots and their pathogenicity and virulence as soilborne pathogens on maize seedlings in South Africa. © 2011 The American Phytopathological Society.


Lamprecht S.C.,Agricultural Research Council Plant Protection Research Institute | Tewoldemedhin Y.T.,Agricultural Research Council Plant Protection Research Institute | Calitz F.J.,Agricultural Research Council Biometry Unit | Mazzola M.,Tree Fruit Research Laboratory
European Journal of Plant Pathology | Year: 2011

Several methods with potential for the management of Rhizoctonia diseases of canola and lupin including plant resistance, fungicide seed treatment and biological control using binucleate Rhizoctonia anastomosis groups (AGs) were evaluated under glasshouse conditions. Screening included the examination of resistance of eight canola and eight lupin cultivars/selections to damping-off and hypocotyl/root rot caused by the multinucleate Rhizoctonia solani AG-2-1, 2-2, 4 and 11. All canola cultivars were highly susceptible to AG-2-1, but Rocket, Spectrum and 44C11 were more resistant than the other cultivars. Spectrum and 44C73 were also more resistant to AG-4 than the other canola cultivars. On lupin, R. solani AG-2-2 and 4 were most virulent, and the cultivar Cedara 6150 and selection E16 were most resistant to AG-2-2; Cedara 6150, E16, Mandelup and Quilinock were more resistant to AG-4 than the other cultivars/selections. The Lupinus luteus selections, E80.1.1.2 and E82. 1. 1 were most susceptible to AG-2-2, 4 and 11. Seed treatment with the fungicides Cruiser OSR (a.i. difenconazole, fludioxonil, metalaxyl-M, thiamethoxam) and SA-combination (a. i. iprodione, metalaxyl, thiram) significantly increased survival of canola and lupin seedlings, decreased hypocotyl/root rot and improved the percentage of healthy seedlings, with the SA-combination being significantly more effective than Cruiser OSR. Application of the binucleate Rhizoctonia AGs (A, Bo, K and I) significantly increased the survival of lupin seedlings inoculated with R. solani AG-2-2 and 4, and AG-I and K significantly improved survival of canola in the presence of AG-4. This is the first report of the potential of binucleate AGs to protect canola and lupin seedlings against infection by multinucleate AGs. © 2011 KNPV.

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