ARC Small Grain Institute

Bethlehem, South Africa

ARC Small Grain Institute

Bethlehem, South Africa
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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.

Oelofse R.M.,ARC Small Grain Institute | Labuschagne M.T.,University of the Free State | van Deventer C.S.,University of the Free State
Journal of Cereal Science | Year: 2010

Bread wheat elite lines and F4 populations were evaluated to determine the influence of genotype and environment on variation in sodium dodecyl sulphate (SDS) sedimentation, and the relation between SDS sedimentation and other quality characteristics. Nine intermediate hard red wheat elite lines and two checks were evaluated for three years over eight locations, and six F4 populations and two hard red wheat checks were evaluated at three locations. In both sets of material, the genotype and location main effect, and genotype × location interaction were highly significant. The genotype component contributed 85.96% of the total variation in SDS sedimentation in the F4 material, and the genotype × location component only 12.87%. In the elite material the contribution of genotype was high enough to make effective selection for SDS sedimentation possible. The genotype × year effect was large, indicating that testing genotypes across years may be more important than across locations. SDS sedimentation was significantly positively correlated with protein content and mixograph development time, and negatively with yield. Selection of higher SDS sedimentation may lead to overly strong dough and lower yields. Therefore a careful approach should be taken in the selection process, balancing the different objectives in a breeding program. © 2010 Elsevier Ltd. All rights reserved.

Ramakuwela T.,ARC Small Grain Institute | Hatting J.,ARC Small Grain Institute | Laing M.D.,University of KwaZulu - Natal | Hazir S.,Adnan Menderes University | Thiebaut N.,ARC Central Office
Journal of Nematology | Year: 2015

Entomopathogenic nematode species differ in their optimum storage temperature; therefore, we conducted a study on the survival and infectivity of the recently described Steinernema innovationi from South Africa at five storage temperatures (5°C, 10°C, 15°C, 20°C, and 25°C) over 84 d using 20,000 infective juveniles (IJ) in 25 ml aqueous suspension containing 0.1% formalin. Our results showed that survival was highest and most stable at 15°C, ranging from 84% to 88% after 84 d. Infectivity of IJ against Galleria mellonella larvae was >90% for all temperatures except for 5°C at which survival decreased to 10% after 84 d. In addition, we stored 2.5 million IJ on a sponge formulation in 15 ml of 0.1% formalin solution for 84 d at the optimum 15°C followed by 2 wk storage at 25°C. Storage of the IJ on a sponge formulation for 14 d at 25°C post 15°C storage for 84 d did not have a detrimental effect on IJ survival (87%) or infectivity to G. mellonella (95%). © The Society of Nematologists 2015.

Preharvest sprouting (PHS) has been recognised as the primary cause of low falling numbers (FNs) in wheat. From recent research it is clear that there are a number of additional causes of low FNs, including late maturity α-amylase. FNs of certain cultivars have varied considerably from year to year and across environments in the wheat producing areas of the Free State Province. In this study we aimed to determine whether climatic conditions could contribute to unexpectedly low FNs. Eleven cultivars were planted over a 5 year period in five different locations in the Free State Province. Total rainfall, minimum and maximum temperatures and growing degree days were determined during six environmental periods. Results from this study indicated that rainfall during the later stages of grain filling and grain maturity had a negative effect on the FNs of 7 of the 11 cultivars, while maximum temperatures during these growing periods were positively correlated with FN in 8 of the 11 cultivars. Minimum temperatures just prior to harvest could also determine the FNs of certain cultivars. Principal component analysis identified three groupings of cultivars varying in the frequency of low FNs experienced over the 5 years of the study. It is clear from this study that rainfall just prior to harvest, and therefore PHS, was not the major factor responsible for the low FNs obtained during this study. © 2012 Springer Science+Business Media B.V.

Dube E.,ARC Small Grain Institute | Fanadzo M.,Cape Peninsula University of Technology
Food Security | Year: 2013

Cowpea (Vigna unguiculata [L.] Walp.) is consumed by many subsistence farmers across the African continent as a cheap source of quality protein. Harvest of cowpea leaves as a vegetable as well as grain from the same plant (dual-purpose) is a primary goal for farmers, which allows them to exploit the nutritional benefits of both. The leaves are consumed in a variety of traditional dishes, or dried for use in the dry season. However, leaf harvest practices by farmers are among the leading causes of poor grain yield and quality. These negative effects can extend to reduction in other benefits of cowpeas such as nitrogen fixation and soil organic matter improvement. This paper critically reviews the effects of leaf harvesting practices on cowpea crops and options available to subsistence farmers to mitigate the negative effects. Recommendations on appropriate timing, duration and intensity of leaf harvesting are then provided, together with agronomic strategies for maximising benefits. Information gaps are also highlighted with the aim of guiding future research programmes for the improvement of the food productivity of cowpea. © 2013 Springer Science+Business Media Dordrecht and International Society for Plant Pathology.

Ramakuwela T.,ARC Small Grain Institute | Hatting J.,ARC Small Grain Institute | Laing M.D.,University of KwaZulu - Natal | Hazir S.,Adnan Menderes University | Thiebaut N.,ARC Central Office
Biocontrol Science and Technology | Year: 2016

Low-cost mass production of entomopathogenic nematodes (EPNs) is an important prerequisite towards their successful commercialisation. This study evaluated six low-cost solid substrate media for in vitro mass production of Steinernema innovationi. Cost analysis was undertaken and an estimated retail price was calculated. This was then compared to the costs of commercial EPN products currently on the market. The highest yield of infective juveniles (IJs) was obtained from a medium containing a puree of house fly, Musca domestica, larvae+ 0.15 g canola oil, (781,678 ± 221 IJs/5 g medium). This medium also had the lowest number of adults remaining in the medium and dead IJs (<10%) at the time of harvest (Day 28). The estimated retail price (R243.27 per 50 million IJs) for S. innovationi produced with our solid culture system was considerably lower than the market price for other Steinernema species products sold by E∼nema, BASF corporation, Koppert, BioBest and Natural Insect Control. The production system developed in this study offers a competitive technology to produce EPN products without having to invest in large-scale liquid fermentation equipment, by using a relatively cheap production medium and simple solid culture growing conditions using Erlenmeyer flasks. © 2016 Agricultural Research Council, South Africa.

Jankielsohn A.,ARC Small Grain Institute
Journal of Economic Entomology | Year: 2016

Russian wheat aphid Diuraphis noxia (Kurdjumov) has spread from its native area in central Asia to all the major wheat-producing countries in the world to become an international wheat pest. Because the Russian wheat aphid is a serious threat to the wheat industry in South Africa, it is important to investigate the key factors involved in the distribution of Russian wheat aphid biotypes and in the changes of the Russian wheat aphid biotype complex in South Africa. There are currently four known Russian wheat aphid biotypes occurring in South Africa. Russian wheat aphid samples were collected from 2011 to 2014 during the wheat-growing season in spring and summer and these samples were screened to determine the biotype status. RWASA1 occurred predominantly in the Western Cape, while RWASA2 and RWASA3 occurred predominantly in the Eastern Free State. Following the first record of RWASA4 in 2011, this biotype was restricted to the Eastern Free State. The surveys suggest that the Russian wheat aphid bioype complex was more diverse in the Eastern Free State than in the other wheat production areas. There was also a shift in Russian wheat aphid biotype composition over time. The Russian wheat aphid biotype complex is dynamic, influenced by environmental factors such as host plants, altitude, and climate, and it can change and diversify over time causing fluctuation in populations over sites and years. This dynamic nature of the Russian wheat aphid will continue to challenge the development of Russian wheat aphid-resistant wheat cultivars in South Africa, and the continued monitoring of the biotypic and genetic structure, to determine genetic relatedness and variation in different biotypes, of Russian wheat aphid populations is important for protecting wheat. © The Authors 2016. Published by Oxford University Press on behalf of Entomological Society of America.

Jankielsohn A.,ARC Small Grain Institute
Journal of Economic Entomology | Year: 2011

Russian wheat aphid, Diuraphis noxia (Kurdjumov) (Hemiptera: Aphididae) was recorded for the first time in South Africa in 1978. In 2005, a second biotype, RWASA2, emerged, and here we report on the emergence of yet another biotype, found for the first time in 2009 The discovery of new Russian wheat aphid biotypes is a significant challenge to the wheat, Triticum aestivum L., industry in South Africa. Russian wheat aphid resistance in wheat, that offered wheat producers a long-term solution to Russian wheat aphid control, may no longer be effective in areas where the new biotypes occur. It is therefore critical to determine the diversity and extent of distribution of biotypes in South Africa to successfully deploy Russian wheat aphid resistance in wheat. Screening of 96 Russian wheat aphid clones resulted in identification of three Russian wheat aphid biotypes. Infestations of RWASA1 caused susceptible damage symptoms only in wheat entries containing the Dn3 gene. Infestations of RWASA2 caused susceptible damage symptoms in wheat entries containing Dn1, Dn2, Dn3, and Dn9 resistant genes. Based on the damage-rating scores for the seven resistance sources, a new biotype, which caused damage rating scores different from those for RWASA1 and RWASA2, was evident among the Russian wheat aphid populations tested. This new biotype is virulent to the same resistance sources as RWASA2 (Dn1, Dn2, Dn3, and Dn9), but it also has added virulence to Dn4, whereas RWASA2 is avirulent to this resistance source. © 2011 Entomological Society of America.

Kutu F.R.,University of Limpopo | Asiwe J.A.N.,ARC Small Grain Institute
African Journal of Agricultural Research | Year: 2010

The productivity of different maize-dry bean intercrop systems (single and double rows of dry bean planted between two maize rows at low and high bean population) was assessed in 2006/07-08 seasons at different fertilizer application regimes (unfertilized control, low, adjusted low and optimum). Sole maize and dry bean plots were included as checks and together with the intercrop systems, they constituted the main treatment while the fertilizer regimes constituted the sub treatment. Treatments were arranged as a split plot design with three replications. There was a significant season x fertilizer interaction effect on maize grain and total biomass yields, and a significant season x cropping system interaction on dry bean grain yield. Grain yield for both crops were significantly (P<0.001) higher in 2007/08 with the highest maize grain yield of 2644 kg ha-1 obtained at optimum fertilizer rate. Dry bean grain yield of 875 and 829 kg ha1 obtained in 2007/08 at optimum and adjusted low fertilizer rates, respectively were comparable. The highest mean grain yield of 2101 kg ha-1 for maize and 728 kg ha-1 for dry bean across the two seasons were obtained in single-bean row intercrop planted at low and high population, respectively. The single dry bean row intercrop system gave the highest productivity based on the total LER values and thus appears the most appropriate for small-scale farmers. © 2010 Academic Journals.

Tolmay V.L.,ARC Small Grain Institute | Jankielsohn A.,ARC Small Grain Institute | Sydenham S.L.,ARC Small Grain Institute
Journal of Applied Entomology | Year: 2013

Host plant resistance can effectively manage Russian wheat aphid (Diuraphis noxia) Kurdjumov (Homoptera: Aphididae) in areas where it is an economically important pest of wheat. However, biotypes of D. noxia virulent on wheat containing resistance gene Dn4 have been reported in both the United States and South Africa. Thirty wheat genotypes, including susceptible Yuma, resistant CItr2401, as well as 25 genotypes containing Dn4 and three genotypes containing Dny were planted under greenhouse conditions in Bethlehem, South Africa, and screened with D. noxia biotype RWASA3. RWASA3 caused susceptible damage symptoms in MTRWA92-145, Ankor, Halt, Bond CL, 18FAWWON-SA 262, Prowers99, 18FAWWON-SA 264, Hatcher, Yumar, Corwa and Thunder CL all reported to contain the Dn4 resistance gene. Genotypes PI586956, Stanton and 18FAWWON-SA 257, containing the Dny-resistance gene were susceptible to RWASA3. Similarly, coinciding development of virulence to resistance genes Dn4 and Dny was reported in the United States. However, in this study, 13 Dn4-containing genotypes showed moderate resistance when screened with RWASA3 alluding to a more complex biotype-gene-interaction. These findings could indicate that Dn4 and Dny may be related and possibly share a similar or common resistance factor. Further studies will be aimed at explaining these results investigating the possibility of an allelic cluster or series for Dn4, possibly including Dny. © 2012 Blackwell Verlag, GmbH.

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