| Variation of agronomic traits of potato somaclones produced by meristem culture | Rosenberg, Viive | 2007 |
KeywordsEstonia, meristem clones, potato, somaclonal variation AbstractFollowing a thermotherapy virus eradication procedure potato plantlets were multiplied as meristem clones in vitro. The agronomic traits of meristem clones were compared in field trials over three years. A total of 16 meristem clones of cultivar Agric dzeltenie and 10 of cultivar Juku were evaluated. There was a significant variation in the number and size of tubers per plant amongst clones. The yield of clones of cultivar Agric dzeltenie varied from 32.4 to 51.41 ha−1 and for cultivar Juku from 27.4 to 33.5 and 6.11 ha−1. Previous studies with other cultivars indicated that meristem clones may differ in starch content of tubers and in disease tolerance. It is possible to improve the agronomic traits of potato cultivars by selecting meristem clones with suitable characteristics. This phenomenon can be used in seed potato production programmes and in plant breeding. AuthorsRosenberg, Viive, Särekanno, Marje, Kotkas, Katrin, Vasar, Virge and Ojarand, Ann Year Published2007 PublicationSouth African Journal of Plant and Soil LocationsDOI10.1080/02571862.2007.10634788 This article contributed by:
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| Variation in the identification of Fusarium spp. in maize samples due to enumerator and growth medium | Flett, B.C. | 2008 |
KeywordsCarnation leaf agar, enumerator, Fusarium spp, Rose bengal-glycerine-urea agar AbstractFusarium spp. have variable phenotypic and morphological features when cultured on different media. Inaccurate identifications could result in variation in the quantification of Fusarium spp. associated with ear rot of maize when two or more researchers identify the same Fusarium isolates based on morphological characteristics. Two hundred and fifty kernels from maize samples collected from each of five localities were surface-sterilized and plated on selective rose Bengal-glycerine-urea (RbGU) medium from which isolates were subsequently transferred to split plates containing Carnation Leaf Agar (CLA) and Potato Dextrose Agar (PDA) for further identification. Three different enumerators independently identified and enumerated Fusarium spp. on RbGU and CLA/ PDA media to determine the relative frequency of Fusarium spp. within maize samples, to compare the accuracy of species identification on different media and to detect and quantify bias among enumerators (inter-enumerator reliability). It was concluded that enumerators were consistent in the identification and quantification of F. verticillioides and F. subglutinans on both RbGU and CLA/PDA media. F. proliferatum enumerations yielded an interaction between locality and enumerator with no significant differences for media. The significant locality x enumerator interaction for F. proliferatum suggests that enumerators had difficulty to distinguish between F. proliferatum and F. verticillioides. The use of RbGU and/or CLA/PDA media were eliminated as a possible source of variation in the identification of Fusarium spp. The inter-enumerator reliability study indicated that Fusarium spp. enumerations by three different enumerators were reliable and accurate and were not a source of variation in the quantification of Fusarium spp. associated with maize ear rot. AuthorsFlett, B.C., Mc Laren, N.W., Mc Donald, A.H. and van Rensburg, B. Janse Year Published2008 PublicationSouth African Journal of Plant and Soil LocationsDOI10.1080/02571862.2008.10639903 This article contributed by:
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| Variasie in lipied- en proteïeninhoud van sonneblomsaad en oliekoekmele in Suid-Afrika | Smith, G. A. | 1989 |
KeywordsChemical composition, lipid content, oilcake meal, protein, sunflower seed AbstractDie variasie in die chemiese samestelling van sonneblom- saad, wat uit verskillende areas aan oliepersers gelewer is, en die invloed daarvan op die samestelling van die geproduseerde oliekoekmele is in die studie ondersoek. Die ontleding van die sade het 'n betekenisvolle variasie in chemiese samestelling van die saad wat deur persers ontvang is, geopenbaar. Die resultate van hierdie studie dui daarop dat die persers wat doeltreffende prosesseringsprosedures toegepas het, in staat was om produkte met die gewenste chemiese samestelling te produseer. AuthorsSmith, G. A., Hayes, J. P. and Smith, Naomi Year Published1989 PublicationSouth African Journal of Plant and Soil LocationsDOI10.1080/02571862.1989.10634513 This article contributed by:
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| Variable tolerance of some crop species to atrazine in various soils | Reinhardt, C. F. | 1993 |
KeywordsAtrazine, carry-over, crop sensitivity, tolerance AbstractThe carry-over of atrazine (2-chloro-4-ethylamino-6-isopropylamino-1,3,5-s-triazine), which occasionally causes damage to susceptible crops grown in rotation with atrazine-treated maize (Zea mays L.), calls for a refinement of the specified recropping intervals. Bioassays were conducted in a glasshouse to evaluate, with nine soils, the tolerance to atrazine shown by dry beans (Phaseolus vulgaris L. cv. Teebus), grain sorghum (Sorghum bicolor (L.) Moench cv. NK222), oats (Avena sativa L. cv. SWK001), soybeans (Glycine max (L.) Merr. cv. Forrest) and sunflower (Helianthus annuus L. cv. S0222). Significant differences between the tolerance of test species in experiments where dry beans/sunflower and oats/soybean combinations were evaluated are inconsistent with the single recrop interval that is stipulated for all four species. The amount of atrazine that was required to elicit a significant response from a particular test crop varied from soil to soil. The variable availability of atrazine in different soils for uptake by crop species needs to be considered to limit the risk when a sensitive follow-up crop is selected for a soil in which the amounts of toxic atrazine residues are known. AuthorsReinhardt, C. F. and Nel, P. C. Year Published1993 PublicationSouth African Journal of Plant and Soil Locations- Bapsfontein, South Africa (-25.9956, 28.3802)
- Ermelo, Mpumalanga, South Africa (-26.518, 29.984)
- Nelspruit, Mpumalanga, South Africa (-25.4658, 30.9853)
- Kroonstad, Free State, South Africa (-27.65, 27.2333)
- Pietermaritzburg, KwaZulu-Natal, South Africa (-29.6006, 30.3794)
- Pretoria, Gauteng, South Africa (-25.7313, 28.2184)
- Viljoenskroon, Free State, South Africa (-27.2122, 26.9555)
- Vryheid, KwaZulu-Natal, South Africa (-27.7669, 30.7934)
- Warmbaths, Pivana, South Africa (-27.5333, 30.8667)
DOI10.1080/02571862.1993.10634668 This article contributed by:
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| Variability among barley landraces in response to waterlogging stress in the greenhouse | Assefa, A. | 2007 |
KeywordsBarley, dry matter, nutrients, waterlogging AbstractBarley production, in some parts of the Ethiopian central highlands, is constrained by seasonal waterlogging. The aim of this study was to investigate differences in growth, nutrient uptake and concentration under waterlogging stress between landraces varying in tolerance. A three week waterlogging treatment was done in the greenhouse and was compared with a free drainage treatment. Waterlogging reduced the total number of tillers per pot of the tolerant landraces Mage and Feleme by 43% and 48%, respectively compared to the control plants while a 23% reduction was seen for the susceptible landrace Feres Gama. Total shoot dry matter accumulation under waterlogged conditions was comparable for all three landraces. Tillers produced by Feres Gama had significantly less dry matter than Mage and Feleme, however. Differences between the susceptible and tolerant landraces in response to waterlogging were largely due to less dry matter accumulation of the tillers and slower growth in the susceptible landrace. Moreover, apparent differences were noticed in N concentration and uptake between the tolerant and susceptible landraces, the effect being less for the tolerant than the susceptible landraces. Difference in N concentration of shoots between the tolerant and susceptible landraces was also observed, though not comparable to that observed in P. AuthorsAssefa, A. and Labuschagne, M. T. Year Published2007 PublicationSouth African Journal of Plant and Soil LocationsDOI10.1080/02571862.2007.10634808 This article contributed by:
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| Validation of the soil evaporation subroutine of the SWB-2D model in a hedgerow peach orchard | Lobit, P | 2004 |
KeywordsHedgerow, micro-lysimeter, peach, radiant transmittance, soil evaporation AbstractThe SWB (Soil Water Balance) model, previously developed to estimate water use by agronomic crops, has been adapted to describe solar radiation interception and soil evaporation in hedgerow orchards. The distribution of solar radiation (Rs) at the soil surface is calculated by the difference between total incoming solar radiation and radiation intercepted by the canopy of the trees. Soil evaporation at different distances from the tree row is calculated as a function of daily potential evaporation, local estimates of Rs, air humidity and humidity of the top soil layer. The soil evaporation routine of SWB-2D was tested using measurements obtained with solarimeter tubes and micro-lysimeters installed across a row in a peach orchard. In an additional experiment to test the lysimeter technique, the micro-lysimeter readings in bare and grass-covered areas in an open field were compared to reference evapotranspiration values calculated by the weather station. Simulated Rs fitted the measurements well, though the dimensions of the tree canopy had to be adjusted to obtain the best fit. Simulated evaporation fitted the micro-lysimeter measurements well in the bare soil area, and the evolution of evaporation patterns during soil drying was reproduced well. In the grass-covered areas, the mulching effect of dormant grass and the continuing transpiration by the active grass should be taken into account in order to accurately simulate soil evaporation. AuthorsLobit, P, Mpandeli, N S, Annandale, J G, Jovanovic, N Z and du Sautoy, N Year Published2004 PublicationSouth African Journal of Plant and Soil LocationsDOI10.1080/02571862.2004.10635053 This article contributed by:
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| Utilization of initially-applied labelled ammonium nitrate by three successive crops | Botha, A.
D.P. | 1992 |
KeywordsLabelled ammonium nitrate, nitrogen balance sheet, utilization AbstractThe aim of the study was to compare N uptake from initially-applied NH4 + and NO3- ions and to compile a balance sheet for applied fertilizer N. In a pot experiment, maize, sorghum and sunflower plants were grown in succession, each for c. 6 weeks, to utilize the mineral N. The treatments were: NH4{NO3}, {NH4}NO3, {NH4}{NO3} and a zero N control, each replicated four times. The ions in brackets were labelled with 15N, Although the applied ammonium nitrate was labelled in three different ways, the same quantity of N was applied initially and similar quantities of total N and soil N were together taken up by the three crops. The N recoveries from the two individual ions, however, differed. Results indicated that on average 75.8% of the initially-applied labelled NH4 +-N was utilized by the vegetative tops of the three crops, this being significantly lower than the 85.9% of the labelled NO3-N utilized. The maize (1st) crop utilized 45.2%, the sorghum (2nd) crop 23.2% and the sunflower (3rd) crop 12.5% of the ammonium nitrate. When both NH4 + and NO3- ions were labelled the N recovery corresponded with the sum of the findings where the ions were separately labelled. The accumulated N uptake by the successive crops from the soil reserves was higher where the soil was fertilized with ammonium nitrate when compared with the controls. The balance sheet took the N in the planted seed and the mineralization of soil N into account. It appeared that the addition of ammonium nitrate stimulated the mineralization of humus in the fertilized pots. The total soil analysis at the end of the experiment indicated that, on average, 17.7% of the fertilizer N remained in the pot soil. Eventually 100%, on average, of the applied ammonium nitrate could be accounted for in the N balance. AuthorsBotha, A.
D.P., Pretorius, D. C., Johnson, J. C. and Kidson, M. V. Year Published1992 PublicationSouth African Journal of Plant and Soil LocationsDOI10.1080/02571862.1992.10634597 This article contributed by:
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| Utility of ear plots versus hill and row plots in wheat breeding programmes | Pakendorf, K. W. | 1988 |
KeywordsEarly generation, ear plots versus hill and row plots, wheat breeding, yield testing AbstractYield testing in early generations of wheat breeding programmes is limited by large numbers of lines and small amounts of seed. This paper compares yield testing using conventional row plots, hill plots and small single-ear plots. The effects of smaller plot size are compensated for by increasing the number of replications when moving from row plots, through hill plots to ear plots. Statistics derived from standard ANOVA's revealed small ear plots to be as useful as larger hill or conventional row plots in assessing the yield potential of lines. In spite of rather large genetic as well as environmental coefficients of variation, ear plots had a lower intra-class correlation coefficient than hill plots or row plots while the repeatability value of ear plots was higher than that of hill or row plots. Spearman rank correlation coefficients showed a highly significant correspondence in the ranking of trial entries in the three systems tested. AuthorsPakendorf, K. W. Year Published1988 PublicationSouth African Journal of Plant and Soil LocationsDOI10.1080/02571862.1988.10634243 This article contributed by:
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| Using the Nearest Neighbour method to substitute missing daily solar radiation data | Bezuidenhout, C. N. | 2002 |
Keywordssolar radiation, nearest neighbour method, missing meteorological data AbstractGround level solar radiation reflects the amount of energy that reaches the earth's surface and is utilised by people, animals and plants. Biological models often require such radiation records for long periods of time, however, a lack of radiation data is common to many countries. Consequently various methods were developed to estimate daily radiation from other meteorological measurements. These methods normally need site specific calibration, require a fixed amount of input variables and do not include uncertainties introduced by global climate change. In this paper an attempt was made to develop a station independent substitution method without sacrificing accuracy. Meteorological data from different climatic regions in South Africa were used to assess the suitability of the Nearest Neighbour (NN) method. This method is based on the re-occurrence of events similar to those in the past. Different statistical approaches were assessed to calibrate the distance equation. An attempt was made to find suitable weights, calibrated universally, for the distance equation that would still produce good estimates for individual stations. The universally calibrated NN method outperformed previously developed equations (locally calibrated) by as much as 20% and overcomes various shortcomings identified in these equations. More detailed analyses also confirmed that the NN approach generates more representative statistical distributions and estimates extreme instances of solar radiation more accurately. AuthorsBezuidenhout, C. N. Year Published2002 PublicationSouth African Journal of Plant and Soil LocationsDOI10.1080/02571862.2002.10634464 This article contributed by:
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| Using morphological characteristics to distinguish between male and female larvae and pupae of the groundnut leafminer, Aproaerema modicella (Deventer) (Lepidoptera: Gelechiidae) | den Berg, J.
Van | 2008 |
KeywordsAproaerema modicella, groundnut leaf miner, invasive pest AbstractAbstract The groundnut leafminer, Aproaerema modicella (Deventer) (Lepidoptera: Gelechiidae) is a well known groundnut pest in Asia. It was first reported in east Africa during 1998 after which it rapidly spread throughout East and southern Africa. The adult is a small brownish-grey moth and it difficult to distinguish between the different sexes even under a stereomicroscope. Research on pest behaviour is hampered by the fact that male and female moths cannot be distinguished. The aim of this study was to identify distinguishing morphological characteristics of male and female larvae and pupae that are visible with the naked eye or under a stereomicroscope. The presence of pink coloured gonads which are easily visible through the cuticle was a distinguishing characteristic of male larvae. The position of the male genital aperture is a useful distinguishing characteristic present in male pupae. It is situated further away from the proximal side of the last abdominal segment, compared to the aperture of oviduct and bursa copulatrix of the female. Authorsden Berg, J.
Van, Walt, A.
van der and Plessis, H.
Du Year Published2008 PublicationSouth African Journal of Plant and Soil LocationsDOI10.1080/02571862.2008.10639915 This article contributed by:
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