| A genetic study of the gametocidal effect of the Lr19 translocation of common wheat | Prins, R. | 1999 |
KeywordsSegregation distortion, responder chromosomes, Sd1, Sd2 AbstractThe Lr19 translocation is preferentially transmitted to the progeny of a heterozygote due to the actions of at least two genes, Sd1 and Sd2 (new designation). However, only Sd2 occurs in the recombinant, Lr19-149, and often causes self-elimination of the recombined translocated segment in heterozygotes. The degree of segregation distortion is determined by the interaction of the Sd genes with polygenes (responder genes) on various wheat chromosomes. In this study suspected responder alleles derived from ‘Inia 66’ or ‘Indis’ (chromosomes 2A, 2B, 3B, 5B, 5D and 6D) appeared mostly to be partially dominant to overdominant over the ‘Chinese Spring’ derived alleles. A specific allele may not necessarily hafe-tfoe same effect (suppression or enhancement) in different genetic backgrounds. Responder genes may not fully compensate for the absence of a homologue in a hemizygote which may then produce effects quite different from those of the homo- and heterozygotes. AuthorsPrins, R. and Marais, G. F. Year Published1999 PublicationSouth African Journal of Plant and Soil LocationsDOI10.1080/02571862.1999.10634838 This article contributed by:
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| A growth model for sugar-cane based on a simple carbon balance and the CERES-Maize water balance | Inman-Bamber, N. G. | 1991 |
KeywordsGrowth model, harvest age, sugar-cane, simulation AbstractThe economic optimum harvest age for sugar-cane depends to a large extent on how rates of photosynthesis and respiration change with age. A simple model of the carbon balance in which a constant photosynthetic efficiency was assumed, accounted to a large extent for dry matter accumulation by cv. NCo376 grown under irrigation. Rain-fed crops of this cultivar were simulated by linking the model of the carbon balance to the CERES-Maize water balance routine. The combined model was validated with data from a comprehensive growth analysis experiment undertaken by staff of the SASA Experiment Station in the 1960's. Dry matter accumulation was explained satisfactorily without changing the coefficients for gross photosynthesis (Pg = 0.082 PAR MJ m−2), maintenance (0.242 Pg) or growth respiration (0.003 × total phytomass). Leaf area index and leaf appearance data indicated that the assumptions regarding leaf area development were valid. The observed fluctuations in water content of the top 300 mm of soil were well explained by the CERES-maize water balance but the gypsum block resistance readings in deeper layers indicated the presence of water that on some occasions was not explained by the model. It was concluded that the sucrose accumulation rate on many farms may have declined because of the recent reduction in the age at harvest in the sugar industry. AuthorsInman-Bamber, N. G. Year Published1991 PublicationSouth African Journal of Plant and Soil LocationsDOI10.1080/02571862.1991.10634587 This article contributed by:
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| A multivariate approach to a specific problem of grouping maize cultivars | Smith, Marie F. | 1990 |
KeywordsAcid tolerance classification, cluster analysis, maize cultivars, multivariate techniques, principal components analysis AbstractThe use of multivariate techniques in the analysis of multivariate problems is illustrated by comparing the results of univariate and multivariate techniques applied to the problem of establishing the nutritional requirements of, and the acid tolerance differences between maize cultivars. Forty-eight maize cultivars were statistically separated into three groups, tolerant, intermediate and intolerant, using a univariate approach. A principal components analysis was then carried out to study the grouping at a multivariate level. The variates included were grain yield, plant height and ten leaf chemical analyses: Al, Mg, P, Ca, K, Mn, Zn, Fe, N and Cu. A non-hierarchical classification was applied to classify cultivars into the three tolerance classes. The univariate method resulted in different groupings for each variate under study, while the multivariate approach ensured one single classification of all cultivars into the three groups. AuthorsSmith, Marie F. Year Published1990 PublicationSouth African Journal of Plant and Soil LocationsDOI10.1080/02571862.1990.10634561 This article contributed by:
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| A preliminary investigation of the potential for maize - legume intercropping in semi-arid area of Sidamo region, Ethiopia. II. Legume response | Alemseged, Y. B. | 1996 |
KeywordsAnnual legumes, intercropping, maize, perennial legumes, semi-arid AbstractAn intercropping trial of maize (Zea mays) with two dual-purpose and two forage legumes was undertaken at Dembela Wacho in the Sidamo region of Ethiopia during the 1987 growing season. The objective was to explore the potential of intercropping in order to improve food security, provide high-quality livestock feed and improve soil stability within the existing Borana cropping system. The legumes examined were two annual dual-purpose legumes, cowpeas (Vigna unguiculata) and lablab (Lablab purpureus), and two forage legumes, cassia (Cassia rotundifolia) and centro (Centrosema schottii). The other treatments imposed were four maize planting densities (0, 20, 35 and 50 thousand plants per hectare) and two legume planting times (at maize planting and 20 days later). Cowpeas produced 55% more grain than lablab. Maize planting density did not affect legume grain yield, but monoculture legume grain yield was about twice that of the intercropped ones. Monoculture cowpea grain yield was reduced by 44% when the planting time was delayed by 20 days while the reduction of lablab was only 12%. On the other hand, lablab grain yield was reduced by 56% due to delayed sowing in the intercrop situation. The dry matter yield of cowpeas and lablab was significantly higher than that of cassia and centro. Monoculture legume dry matter yield was significantly higher than the intercropped legume dry matter yield in all cases. The annual combined maize and legume grain and dry matter yields were higher than those in monoculture, thus showing yield advantages for intercropping. The perennial forage legumes did not appear to reduce maize yield when sown at the same time, suggesting that this practice could be a useful strategy in the last year of a cereal cropping cycle to prevent future soil erosion. AuthorsAlemseged, Y. B., King, G. W., Coppock, L. R. and Tothill, J. C. Year Published1996 PublicationSouth African Journal of Plant and Soil LocationsDOI10.1080/02571862.1996.10634388 This article contributed by:
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| A preliminary investigation of the potential for maize - legume intercropping in the semi-arid area of Sidamo region, Ethiopia. I. Maize response | Alemseged, Y. B. | 1996 |
KeywordsAnnual legumes, intercropping, maize, perennial legumes, semi-arid AbstractAn intercropping trial involving four legumes, three maize planting densities and two legume planting times was undertaken at Dembela Wacho in the Sidamo region of Ethiopia during the 1987 growing season. The objective was to explore the potential of intercropping maize (Zea mays) with legumes within the existing Borana cropping system. The legumes examined were cowpeas (Vigna unguiculata), lablab (Lablab purpureus), cassia (Cassia rotundifolia) and centro (Centrosema schottii). In an ‘average’ growing season for the area, maize grain yield decreased by about 30% when intercropped with both cowpeas and lablab. The effect of cassia and centro was not significant. Legume planting time showed a significant effect on maize grain yield only when the legumes were cowpeas and lablab. Maize grain yield increased by 43% and 36% for cowpeas and lablab respectively when planted 20 days after the maize was sown. Maize planting density had a significant effect on maize grain yield in that yield increased with increased plant population. However, the increase in grain yield was not proportional to the maize planting density. The dry matter yield followed the trend of the grain yield. These results showed that intercropping was more advantageous than sole cropping of maize. Delaying the planting time of cowpeas and lablab after that of maize is recommended, while cassia and centro could be planted together with maize. The best maize planting density under the given conditions was about 55 000 plants ha−1. AuthorsAlemseged, Y. B., King, G. W., Coppock, L. R. and Tothill, J. C. Year Published1996 PublicationSouth African Journal of Plant and Soil LocationsDOI10.1080/02571862.1996.10634387 This article contributed by:
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| A preliminary study of the pollen of Mangifera indica L. cv. Haden in South Africa | de Wet, Esmé | 1986 |
KeywordsPollen, Anacardiaceae, Mangifera, mango dehiscence AbstractThe effect of temperature and light intensity on the dehiscence of anthers of Mangifera indica L. cv. Haden and on the in vitro germination, stainability and viability of mango pollen grains was studied. Pollen of two mango cultivars grown in South Africa was compared, viz. Haden, a shy bearer, and Sensation, a prolific cultivar. Temperature had a marked effect on the tempo of anther dehiscence, irrespective of the light intensity. A 30% sucrose solution yielded the highest mean percentage germination and pollen tube length in both cultivars. The percentage aborted pollen was 31,3% in Haden and 24,5% in Sensation. Pollen from anthers at the moment of dehiscence showed the highest percentage viability of 56,1% in Haden and 81,1% in Sensation. Authorsde Wet, Esmé and Robbertse, P. J. Year Published1986 PublicationSouth African Journal of Plant and Soil LocationsDOI10.1080/02571862.1986.10634197 This article contributed by:
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| A preliminary study to determine water stress tolerance in wild melon (Citrullus Lanatus L.) | Modi, A.T. | 2010 |
KeywordsCitrullus Lanatus, drought tolerance, indigenous crop, pot trial AbstractCommon wild melon (Citrullus Lanatus L.) is an indigenous crop that can contribute to the alleviation of food insecurity as it is an easy-to-grow food source with the potential for processing. The objective of this study was to test the potential of three landraces of common wild melon (‘Brown’, ‘Dark-Brown’ and ‘Very Dark-Brown’, respectively named for seed colour) for drought tolerance under controlled conditions in a glasshouse. Three media (sand, pine bark and a 1:1 mixture of sand and pine bark) were used to grow plants under three water regimes [75%, 50% and 25% Field Capacity (FC)]. Plant growth (height) was determined until plants reached approximately 50% flowering, at which stage biomass was determined. There were significant differences (P < 0.01) between landraces with respect to drought tolerance, as determined by plant growth and biomass. The mixture of sand and pine bark provided the best opportunity (P < 0.05) to grow wild melon under controlled environment conditions compared to sand or pine bark alone. The results of this study will be used as indicator for treatments to be used in a follow-up field experiment where wild melon will be grown during different seasons of the year in Pietermaritzburg, South Africa. AuthorsModi, A.T. and Zulu, N.S. Year Published2010 PublicationSouth African Journal of Plant and Soil LocationsDOI10.1080/02571862.2010.10640004 This article contributed by:
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| A procedure for determining the minimum bulk density of soils | Da C. Nhantumbo, A.
D.J. | 2001 |
Keywordsbulk density, determination soil bulk density, minimum bulk density, soil minimum compactness AbstractThe purpose of this study was to establish a procedure and develop equipment for determining the minimum bulk density of soils. Six soils with silt-plus-clay contents varying between 8 and 41% were selected. The determination consisted of pouring the soil samples into moulds 100 mm high with 106 and 158 mm diameters from three different falling heights, viz. 150, 300 and 450 mm. The uniformity of packing of the soil particles was varied by including or excluding a sleeve equipped with a wire mesh in the procedure. A mould 106 mm in diameter and 100 mm high attached beneath a 150 mm long sleeve which had a wire mesh with 6.5 mm openings fitted 20 mm from the top, was found to be the apparatus producing the most reliable results. It has also been recommended that oven dried soil passed through a 2 mm sieve should be used. AuthorsDa C. Nhantumbo, A.
D.J. and Bennie, A.
T.P. Year Published2001 PublicationSouth African Journal of Plant and Soil LocationsDOI10.1080/02571862.2001.10634401 This article contributed by:
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| A proposed mechanism for the volatilization of ammonia from fertilized neutral to alkaline soils | Du Preez, C. C. | 1986 |
KeywordsAmmonia volatilization, buffer capacity, cation exchange capacity, nitrogenous fertilizers AbstractAmmonia volatilization from five soils, ranging in clay content from 7,6 to 49,9%, were determined after pH values of the soils were adjusted to 8,0. Ammonium sulphate, limestone ammonium nitrate, urea, monoammonium phosphate and diammonium phosphate were applied on the soil surface at levels equivalent to 0,15, 30, 60,120 and 240 kg N ha−1. After a contact period of three days ammonia losses were determined. Ammonia was lost from all soils under all treatments, losses increasing with increasing levels of application. Loss of ammonia from the various fertilizers was ranked as follows: LAN < MAP < (NH4)2)SO4 < DAP < urea. Surprisingly, ammonia losses increased with an increase in clay content or cation exchange capacity of the soil. The apparently anomalous role of the cation exchange complex of the soils to ammonia volatilization can be ascribed to the buffer capacity of the soils. An explanation for the volatilization mechanism is proposed. S. Afr. J. Plant Soil 1986, 3: 31–34 AuthorsDu Preez, C. C. and Burger, R.
du T. Year Published1986 PublicationSouth African Journal of Plant and Soil LocationsDOI10.1080/02571862.1986.10634182 This article contributed by:
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| A quality assurance strategy for wheat (Triticum aestivum L.) where growth environment predominates | van Lill, D. | 1997 |
KeywordsWheat quality, genotype x, environment, multivariate. AbstractThe variation in the processing quality of South African winter wheat cultivars over growth environments is detrimental to its market value. Variation in protein content has previously been identified as a primary contributor to this variation and should therefore be considered in the interpretation of quality data presented during the cultivar release procedure. The aim of the study was to analyse such effects on the interpretation of quality data of advanced wheat lines. Our results indicated a distinctive segregation between entries having higher (≥10%) and lower (<10%) flour protein contents for the three critical phases of commercial processing. The incorporation of a range of localities where both protein levels are sufficiently represented, appeared to be of more importance than the number of harvest seasons over which the entry is evaluated. Finally, multivariate statistical techniques were used to compute user-friendly models for the objective characterisation of variation in milling and rheological quality of wheat lines. The interpretation of genotypic and environmentally related variation was also improved through graphical presentations. The application of these models within the context of deregulation of the wheat industry, is also demonstrated. Authorsvan Lill, D. and Smith, Marie F. Year Published1997 PublicationSouth African Journal of Plant and Soil LocationsDOI10.1080/02571862.1997.10635105 This article contributed by:
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