| Yield retention of resistant wheat cultivars, severely infested with Russian wheat aphid, Diuraphis noxia (Kurdjumov), in South Africa | Tolmay, Vicki L. | 2005 |
KeywordsDamage, Diuraphis noxia, host plant resistance, Triticum aestivum, Yield AbstractRussian wheat aphid, Diuraphis noxia (Kurdjumov), has been a serious pest of wheat in South Africa since 1978. Wheat producers observed that resistant cultivars, developed for control of this aphid, differed in resistance and questioned whether insecticide treatment would be economically justifiable. This study was undertaken to confirm and quantify the observed differences in sixteen resistant cultivars under field conditions. A split-plot field trial with four replicates was planted near Bethlehem, South Africa. The yield of each aphid- infested plot was expressed as a percentage of the yield of the corresponding aphid-free plot giving percentage yield retained after infestation for each cultivar. The percentage yield retained varied in 2000 from 33.0% to 119%; in 2001 from 28.3% to 150.0% and in 2003 from 28.4% to 109.2 %. Cultivars were ranked and classified into more resistant and less resistant groups for each year and an AMMI analysis was conducted. Some cultivars compensated for D. noxia infestation with infested plots giving higher yield than aphid-free plots. It was shown that the level of resistance was not the same in all resistant cultivars and varied dramatically between cultivars and years when measured under severe D. noxia infestation. AuthorsTolmay, Vicki L. and van Deventer, CS Year Published2005 PublicationSouth African Journal of Plant and Soil LocationsDOI10.1080/02571862.2005.10634715 This article contributed by:
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| Yield loss of lentil caused by Uromyces viciae-fabae | Pretorius, Z.A. | 2008 |
KeywordsLens culinaris, loss assessment, rust AbstractYield loss in lentil (Lens culinaris Medik.) due to rust (Uromyces viciae-fabae [Pers.] J. Schröt) was determined by assessing crop and disease parameters at different growth stages and leaf canopy layers in field epidemics at Akaki, Ethiopia. The epidemics were created by inoculation of the rust-susceptible cultivar EL-142 with U. viciae-fabae and spraying plots with tebuconazole at different frequencies. The epidemics produced disease progress curves that varied significantly in the rate (rL ) of temporal progression and area under the disease progress curve (AUDPC). The rust epidemic, in particular between early flowering and early pod formation, had a significant influence on seed yield, pods per plant and seed mass. Mean seed yield losses up to 41.6% were recorded. The number of seeds per pod remained unaffected by the disease. The effect of rust on seed yield of lentil can be predicted with AUDPC and critical-point models using disease severity assessed on the upper canopy layer in the early flowering stage. Every 1% increase in rust severity reduced seed yield by 8.4%. Rust severity ≥ 4.7% at the critical early flowering stage significantly reduced seed yield, and hence, any measure that keeps severity below this threshold level would be advisable. AuthorsPretorius, Z.A. and Negussie, T.G. Year Published2008 PublicationSouth African Journal of Plant and Soil LocationsDOI10.1080/02571862.2008.10639892 This article contributed by:
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| Yield components of samples of two wild Mexican common bean (Phaseolus vulgaris L.) populations grown under cultivation | Bayuelo-Jiménez, J. S. | 1999 |
KeywordsPhaseolus vulgaris, wild common bean, growth habit, yield components, Mexico. AbstractThe common bean (Phaseolus vulgaris L.) is an annual crop legume with wild ancestors distributed from Mexico to northern Argentina. In Mexico, wild populations occur throughout this physiographically and climatically diverse country. Such a wide distribution of common bean populations suggests a large genetic variability with variants adapted to different environments with a wide range of morphological traits. In order to know the response of wild common bean to cultivation this study evaluates the yield components, actual yields and their relationship with the morphological traits, of two such wild bean populations. A sample of these populations from contrasting geographical regions, were grown together in an experimental field in the state of Mexico. They were statistically different in the expression of their growth habits. The two populations differed in leaf area, number of leaves per plant, length of main stem and number of main stem nodes, and number of pods and seeds per plant. All these differences contributed to statistically significant differences in yield. In addition, between populations with different growth habits, yield and yield components were statistically correlated with the same morphological traits. These results suggest that the differences observed in the two wild bean populations depend, at least in part, on the original habitat and that under cultivation, all these differences are likely to increase. AuthorsBayuelo-Jiménez, J. S., Peña-Valdivia, C. B. and Aguirre R., J.
Rogelio Year Published1999 PublicationSouth African Journal of Plant and Soil LocationsDOI10.1080/02571862.1999.10635011 This article contributed by:
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| Yield assessment of advanced wheat breeding lines the Winter Rainfall Region of South Africa. I. Homogeneity of the region | Marais, G. F. | 1985 |
KeywordsBreeding, specific and general adaptation, wheat AbstractThe major wheat-producing areas in the Winter Rainfall Region are geographically divided into the Rûens and Swartland. The question whether the Rûens and Swartland should be regarded as non-similar areas, each meriting its own wheat-breeding programme, is considered. Correlations between cultivar means obtained in the two regions, interaction variance components, the nature of patterns regarding yield at different flowering dates and the similarity in choice of cultivars by farmers in the two areas, all sėem to point to a high degree of similarity. It is concluded that it may not be worth while to conduct separate breeding programmes. S. Afr. J. Plant Soil 1985, 2: 130–134 AuthorsMarais, G. F. Year Published1985 PublicationSouth African Journal of Plant and Soil LocationsDOI10.1080/02571862.1985.10634153 This article contributed by:
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| Yield assessment of advanced wheat breeding lines in the Winter Rainfall Region of South Africa. II. Choosing representative trial sites | Marais, G. F. | 1985 |
KeywordsBreeding, trial sites, wheat, yield testing AbstractAn evaluation of the present system of testing of advanced wheat lines was made in terms of expected genetic gain from selection. Indications are that this system can function quite effectively if properly managed. The feasibility of substituting high potential test sites for low potential test sites in order to facilitate yield testing was also investigated. It was concluded that it may be more appropriate to select test sites on the basis of production intensities, predominant soil types and annual rainfalls. One such solution was derived and is proposed for implementation in the Winter Rainfall Region. S. Afr. J, Plant Soil 1984, 2: 135 −140 AuthorsMarais, G. F. Year Published1985 PublicationSouth African Journal of Plant and Soil LocationsDOI10.1080/02571862.1985.10634154 This article contributed by:
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| Yield and quality response of rose geranium (Pelargonium graveolens L.) to sulphur and phosphorus application | Sedibe, MM | 2012 |
Keywordsoil quality, phosphorus, rose geranium, sulphur AbstractSulphur and phosphorus are essential plant macronutrients. Sulphur is involved in the formation of chlorophyll, activation of enzymes and is part of coenzyme A. Phosphorus forms part of the structure of nucleic acids and phospholipids. Two separate studies were conducted to determine the effects of sulphur and phosphorus levels in nutrient solutions on yield and quality of hydroponically grown rose geranium as well as setting standards of sulphur and phosphorus amounts to be used in the production process. The effect of four levels of sulphur (0.36, 1.90, 3.44 and 4.98 mmol l−1) was investigated in the first study and in the second study four levels of phosphorus (0.1, 0.8, 1.5 and 2.2 mmol l−1) were also investigated. All treatments were assigned in a completely randomised block design with five replicates. The results of the first study showed a significant effect of sulphur on the number of branches, plant height and foliar fresh mass. Foliar fresh mass and oil yield peaked at the 3.44 mmol l−1 concentration. The second study showed that plant height and the number of branches was not affected significantly by phosphorus, but foliar mineral phosphorus, magnesium and potassium were affected. Oil yield of rose geranium increased linearly with increased phosphorus concentrations. Both the guaia-69-diene content and the citronellol:geraniol ratio were greater at the highest phosphorus level, which indicated that oil quality can be enhanced by using relatively high phosphorus concentrations in nutrient solutions. AuthorsSedibe, MM and Allemann, J Year Published2012 PublicationSouth African Journal of Plant and Soil LocationsDOI10.1080/02571862.2012.744108 This article contributed by:
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| Yield and quality of flue-cured tobacco (Nicotiana tabacum L.) as affected by calcium, magnesium, potassium and boron | Combrink, N.
J.J. | 1988 |
KeywordsBoron, magnesium, ripeness, texture, tobacco AbstractA field trial was carried out with flue-cured tobacco on a Shorrocks soil series at the Loskop research station. Different levels of K, Ca and Mg in the soil were obtained after two annual applications of these cations in the sulphate form. Averages for the three K levels in the top (300 mm) soil were 148,192 and 216 mg kg−1. The three Ca levels averaged 646,706 and 835 mg kg−1 and two Mg levels were 143 and 187 mg kg−1. The pH (water) varied between 5,3 and 5,4. The highest Ca level produced greener leaves with significantly more chlorophyll and higher nicotine levels when harvested. Both Ca and Mg increased leaf mass interactively. The higher Mg level adversely affected the texture of the cured leaf which was aggravated by the higher Ca levels. A single foliar application of boron (1 kg B ha−1) during the early flower bud stage increased the B content of the top leaves from 30,0 to 33,6 mg kg−1 and improved their texture. K applications did not significantly affect yield or quality, possibly due to a relatively high natural K content of the soil. AuthorsCombrink, N.
J.J. Year Published1988 PublicationSouth African Journal of Plant and Soil LocationsDOI10.1080/02571862.1988.10634279 This article contributed by:
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| Witloof chicory (Cichorium intybus L.) root vernalization by means of exogenously supplied gibberellic acid | König, R. | 2002 |
Keywordschicory, gibberellic acid, vernalization, witloof AbstractEndogenous gibberellic acid (GA) is known to play a pivotal role in the vernalization process of plants requiring a cold induction. In order to establish the effect of an exogenous GA application on the vernalization process of chicory roots, GA was applied to five cultivars (two ‘late’ types and three ‘early’ types) of witloof chicory (Cichorium intybus L.). GA was applied as leaf as well as root treatments, each at high and low concentrations. Chicon quality was subsequently measured and used as an arbitrary indicator for completed vernalization. Lateral root formation was monitored as an indicator for possible damage to the external cells of the main roots. Irrespective of GA concentration, no significant difference in chicon quality was observed with the leaf treatment, compared to the untreated control. Both root treatments, on the other hand, decreased chicon quality significantly, but, despite cultivar differences, had no effect on lateral root formation. Exogenous GA treatments, at the levels used in this study, did not enhance chicon quality and thus vernalization. AuthorsKönig, R. and Combrink, N.
J.J. Year Published2002 PublicationSouth African Journal of Plant and Soil LocationsDOI10.1080/02571862.2002.10634435 This article contributed by:
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| Winter cover crops effects on soil strength, infiltration and water retention in a sandy loam Oakleaf soil in Eastern Cape, South Africa | Mupambwa, HA | 2012 |
Keywordslupin, oats, plant available water, vetch, water infiltration rate AbstractThere is substantial evidence that cover crops increase soil fertility and plant nutrition but the few studies concerning soil physical properties are conflicting. This study determined the effects of monocultures of vetch (Vicia dasycarpa L.), lupin (Lupinus angustifolius L.), oats (Avena sativa L.) and bicultures of oats and vetch and a weedy fallow on the strength and water conservation properties of a hardsetting Oakleaf soil. Oats monoculture lowered the soil strength by 48.5%, whilst vetch and lupin increased soil strength by 43% and 31%, respectively, relative to the control. Bicultures decreased soil strength as the proportion of oats increased. Oats monoculture increased cumulative water infiltration relative to the control. Bicultures increased the water final infiltration rate by 105–163% compared to the control. Plant available water increased by 24–28% compared to the weedy fallow under monocultures. However, no significant differences were observed on plant available water after two rotations with bicultures compared to the weedy fallow. We concluded that oats monoculture reduced the strength and improved water conservation properties of the hardsetting soil but vetch and lupin monoculture worsened the deleterious effects of the hardsetting phenomenon. AuthorsMupambwa, HA and Wakindiki, IIC Year Published2012 PublicationSouth African Journal of Plant and Soil LocationsDOI10.1080/02571862.2012.722697 This article contributed by:
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| Winter cover crops and fertiliser effects on the weed seed bank in a low-input maize-based conservation agriculture system | Dube, E | 2012 |
Keywordsgrazing vetch, mulch effects, oat, problematic weeds AbstractThis study investigated the effects of grazing vetch (Vicia dasycarpa L.) and oat (Avena sativa L.) cover crops and fertiliser on the seed bank of some problematic weeds in a maize-based conservation agriculture system. Soil sampling for seed bank analysis was carried out at the 0–5 and 5–20 cm depths after four years of rotations. The winter cover crops reduced the seed-bank density of Digitaria sanguinalis (L.) Scop., Eleusine indica (L.) Gaertn., Amaranthus retroflexus L. and Datura stramonium L. in the 0–5 cm depth by 30–70%. Vetch was more effective on depleting the D. sanguinalis seed bank than oat. Fertiliser application reduced the A. retroflexus seed bank by 41.6% in the weedy fallow, but had no significant effect in plots grown to the cover crops. The winter cover crops did not significantly affect seed-bank weed species diversity. AuthorsDube, E, Chiduza, C, Muchaonyerwa, P, Fanadzo, M and Mthoko, TS Year Published2012 PublicationSouth African Journal of Plant and Soil LocationsDOI10.1080/02571862.2012.730637 This article contributed by:
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