1,721,019 research outputs found
Comparison of the Contents of Bioactive Compounds and Quality Parameters in Selected Mango Cultivars
Full text linkMango cultivars Tommy Atkins, Zill, Peach, Sabre, Rosa and Phiva were analyzed for their quality parameters (fruit weight, flesh color chroma, L, h0, total soluble solid [TSS]/titratable acidity [TA], firmness), bioactive compounds (total phenols, carotenoids, ascorbic acid, antioxidant activity) and polyphenol oxidase (PPO) activity. Cv. Sabre showed highest total phenolic content (76.43 mg gallic acid/100 g FW), carotenoids (9.90 mg/100 g of FW), ascorbic acid content (69.71 mg/100 g of FW) and antioxidant activity (1.2 mg of gallic acid/g of FW), whereas cv. Peach mango contained lower bioactive compounds. Multivariate principal component analysis analysis showed higher concentration of bioactive compounds in cv. Sabre mango, whereas cv. Tommy Atkins was firm and heavier. Cv. Rosa and Phiva were moderately rich in bioactive compounds and lower in fruit weight and firmness, whereas cv. Peach was higher in TSS/ TA. The PPO activity was higher in cvs. Rosa and Zill.Instituto de Tecnología de AlimentosFil: Sellamuthu, Periyar Selvam. Tshwane University of Technology. Department of Crop Science. Postharvest Technology Group; SudáfricaFil: Denoya, Gabriela Inés. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Tecnología de Alimento. Laboratorio de Compuestos Proteicos; ArgentinaFil: Sivakumar, Dharini. Tshwane University of Technology. Department of Crop Science. Postharvest Technology Group; SudáfricaFil: Polenta, Gustavo Alberto. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Tecnología de Alimento. Laboratorio de Compuestos Proteicos; ArgentinaFil: Soundy, Puffy. Tshwane University of Technology. Department of Crop Science. Postharvest Technology Group; Sudáfric
Evaluation and selection of 20 sorghum [Sorghum bicolor (L.) Moench] genotypes for drought tolerance
Full text linkDissertation (MInstAgrar)--University of Pretoria, 2010.A field study was conducted at ARC - Grain Crops Institute, Potchefstroom Experimental Farm and at Taung Crop Production Center during 2006/07 summer growing season. Twenty sorghum genotypes were planted in two separate blocks, under full irrigation and rain fed conditions with plot size of 4 rows x 5 m x 0.9 m giving a density of 55 555 plants ha-1. The experiment was laid out in a randomised complete block design replicated three times. The irrigated block received scheduled irrigation from planting until maturity, while the rain fed block received irrigation prior to germination only. Agronomic traits measured were plant height, stem diameter, biomass, flowering date, panicle exertion, panicle length, leaf area, grain yield, and thousand seed mass at Potchefstroom and Taung experiments. Drought susceptibility index (DSI) was quantified using the formula: DSI = [1 - (Ydi/ Ypi)]/ [1 - (YD/YP)] and %yield reduction (%YR) was calculated using the formula: %YR = (Ypi –Ydi)/ Ypi x 100. Significant variations among genotypes with regard to grain yield (GYLD), plant height (PH), panicle length (PL), biomass (BM), stem diameter (SD), panicle exertion (PEx), and 1000 seed mass (TSM) were observed at Potchefstroom under rain fed conditions, while under irrigated conditions significant variations were only observed for GYLD, PH, PL, BM, days to 50% flowering (DF), SD, leaf area (LA), PEx and TSM. At Potchefstroom genotypes varied significantly with regard to PH, PL, BM, DF, SD, LA, PEx and TSM under rain fed conditions, while under irrigated conditions genotypes varied with all traits measured with exception of harvest index (HI) and relative water content (RWC). At Potchefstroom, soil water deficits significantly affected GYLD, PH, HI, PEx and RWC, while at Potchefstroom soil water deficits significantly affected GYLD, PH, SD, LA, PEx, TSM and RWC. Genotypes varied with their level of resistance/ susceptibility to soil water deficits at both Potchefstroom and Taung. Some remarkable correlations among traits measured were observed under rain fed and irrigated conditions and across the treatments at both Potchefstroom and Taung. At Potchefstroom, significant correlation was only observed between drought susceptibility index (DSI) and PH under rain fed conditions, while at Potchefstroom negative and significant correlation was only observed between DSI and GYLD under rain fed conditions. At Potchefstroom, GYLD under rain fed significantly related to GYLD under irrigated conditions and across the treatments. However, GYLD under irrigated conditions significantly related to GYLD across the treatments. At Potchefstroom, GYLD under rain fed conditions significantly correlated with GYLD across soil water regimes, while GYLD under irrigated conditions significantly correlated with GYLD across the treatments. Genotypes that exhibited the combination of high yield potential and resistant traits were recommended. Genotypes that exhibited high resistant traits with low yield potential were recommended for breeders to incorporate those traits into susceptible genotypes with high yield potential.Plant Production and Soil Scienceunrestricte
Mulching, plant population density and indigenous knowledge of wild ginger (Siphonochilus Aethiopicus)
No full textDissertation (M Inst Agrar (Plant Production: Agronomy))--University of Pretoria, 2007.Please read the abstract in the section 00front of this documentPlant Production and Soil ScienceM Inst Agrarunrestricte
Response of fever tea (Lippia Javanica)to fertigation frequency, growth medium and propagation method
Full text linkDissertation (MSc (Horticulture))--University of Pretoria, 2007.Fever tea is one of the important medicinal plants belonging to the family Verbenaceae. The leaves of the plant are used as a remedy to treat malaria, stomach pains, colds and fever. There are different clones of Lippia species available with different medicinal value. Therefore, the purpose of this study was to determine protocols for propagation of fever tea so as to multiply an ideal clone. Vegetative propagation of this plant species by stem cuttings, requirements for seed germination and response of fertigation frequencies and growing medium to growth, yield and quality has not been studied. In this study, factors influencing effective propagation of fever tea were studied. Those factors were: cutting position (apical vs. basal), media (pine bark vs. sand), hormone (seradix No. 2 vs. no hormone) light and temperature requirement for fever tea seed germination and effect of fertigation frequencies (0.4 L/day, 1L/day, 2L/day, 2L/2nd day and 2L/week) and growing media (pine bark vs. sand) on growth, oil yield and oil quality. In vegetative propagation by stem cuttings, measurements made were number of roots per rooted cutting, fresh mass, stem circumference and number of leaves and the rate of rooting during four consecutive sampling dates (5, 10, 15 and 20 days after planting). Apical cuttings rooted earlier by 5 days than basal cuttings at 10 days but at 15-20 days after establishment, both cuttings had good rooting. Fresh mass was not affected by cutting position and rooting media, but cuttings performed slightly better when propagated in pine bark medium than sand medium. Basal cuttings resulted in thicker stems and more leaves as compared to apical cuttings. Seradix No.2 (0.3% IBA) hormone increased the fresh mass, stem circumferences, root number and leaf numbers on both apical and basal cuttings. For the establishment of fever tea stem cuttings, both apical and basal cuttings can be used but pine bark is the ideal medium. The cuttings can be ready for transplanting in 15-20 days after establishment and Seradix No. 2 (0.3% IBA) promotes rooting of fever tea cuttings. The ideal combination of light and temperature for seed germination of fever tea was investigated. Germination was tested at constant temperature regimes (15, 20, 25 and 30¨¬C with continuous light or dark period and alternating temperatures of 20:30 and 16L: 8D (light: dark) combinations respectively. Seeds started to germinate after 8 days from incubation and the last germination was observed at 30 days from incubation. Germination percentages increased at 20-30 constant temperatures and 20/30 alternating temperatures but the difference amongst them was not significant. Higher germination of 86% were achieved when seeds were exposed to continuous light than alternating light and dark. Seeds failed to germinate in continuous darkness. Fever tea seeds were positively photoblastic. The effect of fertigation frequency and growing medium on the growth, yield and quality of fever tea were investigated in a tunnel. Treatments used were five fertigation frequencies (0.5L/day, 1L/day, 2L/day, 2L/2nd day, and 2L/week) and two growing media (pine bark and sand). Measurements made were plant height, stem circumference and number of branches at 8, 16 and 32 weeks after planting. At 8 weeks after planting all fertigation frequencies improved fever tea growth except fertigation frequency of 2L/week. All the fertigation frequencies were ideal to sustain the growth and development of fever tea plants except 2L/week. At 16 weeks after planting there were interactive effects between fertigation frequencies and the growing medium for the plant height of fever tea. Plants fertigated with 2L/day grown in sand media grew taller than all the other fertigation frequencies. At 32 weeks after planting there was a significant effect on the plant height from the main effects of fertigation frequency and growing medium. Plants fertigated with 2L/day were significantly the tallest followed by plants fertigated with 0.5L/day, 1L/day, 2L/2nd day and 2L/week. When plants were younger better plant growth was obtained in pine bark media. Stem circumference and number of branches of fever tea were significantly affected by fertigation frequency and growth medium. At 16 and 32 weeks after planting, plants grown in sand media had thicker stems and more branches as compared to plants grown in pine bark media. The essential oil of fever tea was extracted using hydro-distillation. Fertigation frequency did not affect oil yield. Plants grown in pine bark media yielded more oil than plants grown in sand medium. Microscopical studies using scanning electron microscope were investigated to determine the development of oil glands and trichomes on the abaxial (upper) and adaxial (lower) surfaces of the leaves as affected by fertigation frequency and the growing medium. There were no significant effects on the number of oil glands and trichomes developed on both surfaces of the leaves. Pine bark medium resulted in larger oil glands than sand medium regardless of the treatments, and pine bark also yielded more oil percentages than sand medium. Based on this investigations for commercial production of fever tea essential oil pine bark media is recommended. Chemical compounds of fever tea oil were also not affected by fertigation frequency or growth medium. In this study the chemical compounds detected from essential oils of fever tea were monoterpenes (i.e. ¥á-pinene, sebinen, 1.8 cinede, myrcene, ipsenone and ipsedienone) and the sesquiterpenes (i.e. ¥â-caryophyllene and germacrene-D). Compounds that gave the smallest chemical percentages and the shortest time to be detected were ¥á-pinene, sebinen, 1.8 cinede, myrcene, ipsenone and ipsedienone. Compounds found with the highest chemical percentages with highest peaks were ¥â-caryophyllene and germacrene-D.Plant Production and Soil Scienceunrestricte
Seasonal patterns of vegetative growth and photosynthesis in mango (Mangifera Indica L.) trees
Full text linkDissertation (MInst Agrar (Horticulture))--University of Pretoria, 2006.Shoot growth and leaf photosynthesis of 6-7 year-old, field-grown mango (Mangifera indica L. cv ‘Kent’) trees subjected to the following irrigation regimes were monitored during the season of 2002/2003: Co, control (±95% of field capacity, FC); DI-1 and DI-2, continuous deficit irrigation (±79% and ±69% of FC, respectively); RDI, regulated deficit irrigation (like Co except that irrigation water was withheld for 2 weeks in Dec 2002/Jan 2003 during the final stage of fruit growth); and Co-F, farm control, full irrigation when soil moisture was lower than -10 KPa). During the post-harvest flushes in 2002 and 2003, Co-F shoots showed 56% more shoot volume and dry mass than Co indicating that a large amount of irrigated water was used for such vigorous growth. There were no significant differences in the number of flowering canes between all irrigation treatments during the flowering flush in 2002. However, the pattern of decreasing numbers of flushing terminals and shoot numbers was concurrent with decreasing amounts of irrigation water applied (Co-F>Co>RDI>DI-1>DI-2). The results indicated that part of the irrigation water applied to Co-F was used for vigorous vegetative growth; while in the DI-2 treatment severe shoot growth reduction seemed to seriously hinder productivity. Midday leaf assimilations in well-irrigated ‘Kent’ mango trees in the field during winter and spring amounted to (4.5 ± 0.6 and 5.9 ± 0.3 µmol CO2 m-2 s-1, respectively) and were lower than in autumn and summer (6.4 ± 1.8 and 11.1 ± 0.8 µmol CO2 m-2 s-1, respectively). Differences in mean photosynthetic (Pn) rates between the three field-grown and well-irrigated cultivars, ‘Kent’, ‘Keitt’ and ‘Heidi’, were not significant except for January and April 2003. Young leaves (<25 DABB, days after bud break) photosynthesized only to a small extent in winter and summer at midday (0.2 ± 0.9 and 0.4 ± 0.3 µmol CO2 m-2 s-1, respectively). However, high Pn rates at midday were reached in leaves aged 90-180 DABB in summer (10.3 ± 2.0 µmol CO2 m-2 s-1) and maintained at leaves that were older than 365 DABB (10.4 ± 0.7 µmol CO2 m-2 s-1), while those in winter were lower for both leaf age groups (3.2 ± 0.6 and 3.5 ± 0.8 µmol CO2 m-2 s-1, respectively). In field-grown ‘Kent’ mango trees, water deficit reduced significantly the photosynthetic capacity in the irrigation treatment DI-2 across the entire year, especially during late spring and early summer, in comparison to the Co-F treatment, while differences between the treatments Co, DI-1, and RDI were negligible (in the range of 7.0-7.3 µmol CO2 m-2 s-1) across the entire year. Generally, the Co-F treatment maintained slightly higher photosynthetic rates (7.9 ± 3.2 µmol CO2 m-2 s-1) over the entire year than the other treatments showing that they received more water. Nevertheless, DI-2 maintained reasonable rates (6.5 ± 1.7 µmol CO2 m-2 s-1), even though they were severely stressed indicating that those trees apparently adapted to low water regimes by increasing their water use efficiency.Plant Production and Soil Scienceunrestricte
Growth, yield and quality of tomatoes (Lycopersicon Esculentum Mill.)and lettuce (Lactuca Sativa L.) as affected by gel-polymer soil amendment and irrigation management
Full text linkDissertation (MSc (Horticulture))--University of Pretoria, 2005.Tomato and lettuce are amongst the most important fresh vegetables used in South Africa. However, growth, yield and quality of tomato and lettuce are constrained by water shortage and poor productivity of sandy soil. In South Africa, large parts of the agricultural land are in a semi-arid region and water is becoming scarcer and more costly. Recognizing the fundamental importance of water-holding amendments like gel-polymers to enhance water use efficiency and soil physical properties, this study was carried out to investigate the effects of pure gel-polymer and fertiliser-fused gel-polymer soil amendments across five irrigation intervals on growth, yield and quality of tomato (Lycopersicon esculentum Mill.) and lettuce (Lactuca sativa L.). The response of tomato growth, yield and quality to irrigation interval and gel-polymer soil amendments (pure gel-polymer and fertiliser fused gel-polymer) was conducted in a tunnel. The gel-polymer treatments were: control (sandy soil), two pure gel-polymer levels (8 and 16 g-20 L-1 sandy soil, equivalent to 400 g and 800 g-m-3) and two fertiliser fused gel-polymer levels (20 and 40 g-20 L-1 sandy soil, equivalent to 1 kg and 2 kg-m-3). Irrigation was either applied once daily or every second, third, fourth or fifth day, equivalent to 0.8, 1.25, 1.45, 1.88 and 2.29 L of water per 20 L bag of sand. Fruit mass, fruit diameter, fruit number, plant height, stem diameter, number of trusses, root fresh and dry mass, total soluble solids, fruit juice pH and titratable acidity were determined. Neither irrigation interval nor gel-polymer amendments had an influence on tomato quality (total soluble solids, pH and titratable acidity). Generally, plant yield, height, stem diameter, number of trusses, and root fresh and dry mass were increased with gel-polymer amendments compared to pure sandy soil. Regardless of irrigation interval, both fertilizer-fused gel-polymer levels appeared to be effective in improving plant growth and yield compared to pure gel-polymer, which gave good results only at the higher level of application. The study revealed that gel-polymer amendments increased productivity of tomato on a sandy soil. Similarly, the response of lettuce growth, yield and quality to gel-polymers and irrigation intervals was investigated under a tunnel conditions. The gel-polymer treatments were: control, two pure gel-polymer levels (4 and 8 g-10 L-1 sandy soil, equivalent to 400 g and 800 g-m-3) and two fertilizer-fused gel-polymer levels (10 and 20 g-20 L-1 sandy soil, equivalent to 1 kg and 2 kg-m-3). Irrigation was either applied daily or every second, third, fourth or fifth day, equivalent to 0.63, 0.83, 1.04, 1.25 and 1.46 L per 10 L plastic bags. Measurements were made of fresh head mass, head height, head circumference, head diameter, stem diameter, fresh root mass, dry root mass and dry head mass. The dried head samples were analysed for percentage tissue calcium and nitrogen. Lettuce grown on sandy soil amended with higher level of pure gel-polymer (Stock 8) and both fertiliser fused gel-polymer levels (Aqua 10 and 20) resulted in significantly higher fresh and dry head mass, head circumference, head diameter, head height, stem diameter, and fresh and dry root mass as compared to low level of pure gel-polymer (Stock 4) and sandy soil without gel-polymer (control). All irrigation intervals did not have an effect on growth, yield and quality of lettuce except at irrigation interval of every third day, which significantly lowered head circumference. Gel-polymer did not have a significant effect on percentage calcium and nitrogen concentration in the leaf tissue. Growing lettuce in soil amended with higher pure gel-polymer (Stock 8) level and both fertiliser-fused gel-polymer (Aqua 20 and Aqua 40) would likely be economically advantageous for a grower due to improved growth and higher yield of good quality lettuce.Plant Production and Soil Scienceunrestricte
Growth, anatomy, quality and yield of wild ginger (Siphonochilus aethiopicus) in response to nitrogen nutrition, fertigation frequency and growing medium
No full textDissertation (MSc (Plant Production))--University of Pretoria, 2004.Please read the abstract in the section 00front of this document.Plant Production and Soil Scienceunrestricte
Response of cabbage (Brassica Oleracea Var Capitata) transplants to nitrogen, phosphorus and potassium nutrition
Full text linkDissertation (MSc (Agric))--University of Pretoria, 2006.Please read the abstract in the dissertationPlant Production and Soil Scienceunrestricte
Essential oil yield and composition of rose-scented geranium (Pelargonium sp.) as influenced by harvesting frequency and plant shoot age
Full text linkDissertation (MSc(Agric) (Agronomy))--University of Pretoria, 2007.No abstract availablePlant Production and Soil ScienceMSc(Agric)unrestricte
Seedling quality, plant growth and fruit yield and quality of tomato (Solanum lycopersicum L.) in response to Trichoderma harzianum and arbuscular mycorrhizal fungi
Full text linkThesis (PhD)--University of Pretoria, 2012.Existing evidence suggested that nursery inoculation with Trichoderma harzianum and arbuscular mycorrhizal fungi (AMF) could reduce deleterious effects of biotic and abiotic stresses and improve seedling quality, fruit yield and quality of tomato (Solanum lycopersicum L.). However, studies of their combined inoculation on seedling growth, fruit yield and quality of tomato plants are not well-documented. Experiments were carried out to investigate the combined effect of T. harzianum and AMF on tomato crop performance under various conditions. When combined with a T. harzianum and AMF mixture, seaweed extract from Ecklonia maxiama inhibited AMF root colonisation of tomato seedlings. Treating seedlings with a mixture of T. harzianum and AMF reduced the incidence of Verticillium wilt in tomato grown in a nethouse at early season, with negligible effect on fruit yield. Further investigations were initiated to find out whether T. harzianum and AMF were efficient when applied as a mixture or alone, at different inoculation times. Co-inoculation with T. harzianum and AMF (Glomus mosseae) improved seedling growth and development, except when both fungi were simultaneously applied two weeks after sowing. When the seedlings were allowed to grow up until full harvest in a greenhouse, both fungal inoculants increased total yield and marketable yield, but these increases were not significant. Furthermore, inoculation with AMF increased the percentage of extra-large fruit. Field experiments conducted under commercial tomato production confirmed greenhouse studies. Inoculation of tomato with T. harzianum and AMF, either alone or in combination increased early fruit yield (four first harvesting weeks). Throughout the studies, percentage AMF root colonisation in seedlings and plants remained low, despite nursery inoculation. Field experiments investigated the effects of AMF-inoculated transplants combined with biochar-amended soils on AMF root colonisation and their resultant effects on overall crop performance and microbial community structure. Biochar had no effect on AMF root colonisation, and also when combined with AMF, it had no influence on tomato productivity. Interestingly, biochar altered the fungal community while AMF might have influenced the bacterial community such as plant-growth promoting rhizobacteria, which are associated with improved plant growth, nutrient uptake and disease control in the rhizosphere. These benefits could contribute to improved yield and fruit quality. In conclusion, although the results were variable, there was a clear indication that T. harzianum and AMF can play an important role in tomato production.Plant Production and Soil Scienceunrestricte
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