Thesis (MSc .(Plant Production)) -- University of Limpopo, 2016 / Delayed fruit harvest (DFH) or on-tree-fruit storage is a strategy being considered to extend the harvest season of late maturing ‘Reed’ avocado. However, avocado fruit growth beyond physiological maturity is accompanied by alterations in chemical and physical properties. Thus, the study aimed to investigate the effects of delayed harvest on tree productivity, mineral nutrition and post-harvest quality of late maturing ‘Reed’ avocado and further to evaluate the fruit quality response to varying ripening temperature regimes. As treatments, fruit were harvested early, mid and late in the season, with one month apart from each harvest during 2013 and 2014 seasons. Yield and fruit size were recorded at harvest. During each harvest time, two sets of fruit samples were collected to determine the fruit nutritional content while the second set was cold stored at 5.5°C for 28 days. After storage, fruit were ripened at 16, 21 or 25°C and evaluated for post-harvest disorders, pathological diseases and fruit physico-chemical properties. Yield dropped from 42 to 12 kg/tree from early to late harvest during 2013, while treatments showed no effect during 2014. Furthermore, treatments had no effect on fruit size during both seasons. Phosphorus content decreased by 40 and 23% from early to late harvest time during 2013 and 2014 seasons, respectively. Similar decreasing patterns were observed for K, Ca and Mg content. Zinc content remained constant during 2013; however, mid-season fruit maintained higher zinc levels during 2014 season when compared to early and late harvest time. Protein content was constant for early and mid-season fruit but significantly decreased during the late harvest in both seasons. Moisture content decreased from 74.0 to 65.0% from early to late harvest during both seasons. Starch, oil and ash content were high during late harvest time in both seasons; while crude fibre was high during the mid-harvest time when compared with early and late harvest time. Internal chilling injury increased with maturity and ripening temperature. In both seasons, higher temperatures induced higher anthracnose incidences during early and mid-harvest compared with late harvest time. Similarly, vascular browning was high on fruit ripened at 16°C during early and mid-harvest time but decreased on late harvest fruit during 2013. However, low ripening temperatures induced high incidences of vascular browning during 2014 season. Stem-end rot was high on fruit ripened at 16°C than 21 and 25°C during 2014 season. xvi Physico-chemical quality parameters showed similar behaviour in both seasons. Fruit lightness increased with ripening time regardless of ripening temperature during the early harvest, but remained constant during mid and late harvest. Hue angle (h0) and Chroma (C*) values were slightly reduced during ripening. Fruit ripened at 25°C had the highest respiration rate and reached a climacteric peak earlier (day 2) than fruit ripened at 21 and 16°C (day 4). Fruit firmness and weight loss were high and rapid at 25°C followed by 21 and 16°C regardless of the harvest time. Delayed harvest had no effect on yield and fruit size. Generally, nutritional content of avocado fruit increased with fruit maturity. Furthermore, fruit maturity played a major role in the response of fruit to ripening temperature. Higher temperature enhanced fruit ripening, but was conducive for development of post-harvest diseases. Keywords: Harvesting time, nutrition, yield, fruit size, ripening temperature, post-harvest quality

Call number: LD2668 .T4 1986 D52 / Master of Science / Animal Sciences and Industry

Thesis (MScAgric)--Stellenbosch University, 1992. / One microfiche copy / ENGLISH ABSTRACT: The possibility of harvesting grapes at an earlier stage of maturity, based on differences in glucose and fructose concentration which influence the sweetness of grapes, was investigated. Although differences between cultivars were found the extent was not such that a specific cultivar could be selected in order to harvest at a lower sugar concentration, but with the same sweetness. Certain characteristics of table and wine grape cultivars with respect to anatomical composition and skin penetration resistance (SPR) were also investigated in order to ascertain the extent to which grapes would resist external damage, and to what extent turgor and skin thickness contributed to SPR. Daily variances in SPR confirm that not only skin strength, but also the turgor of the grape berry contributed to SPR. Skin penetration resistance seems to be a good criterion of the extent to which cultivars would resist external damage, because it is based on the toughness of the skin and the turgor of the berry. / AFRIKAANSE OPSOMMING: Die moontlikheid van vroeer oes op grond van verskille in die glukose- en fruktosekonsentrasie wat 'n invloed op die soetheid van druiwe mag he, is ondersoek. Daar is gevind dat die verskille wat tussen cultivars voorkom nie van so 'n grootte-orde is dat 'n spesifieke cultivar geselekteer kan word ten einde by 'n laer totale suiker, maar by dieselfde soetheidsgraad, te kan oes nie. Verder is sekere eienskappe van tafel- en wyndruifcultivars t.o.v. anatomiese samestelling en doppenetrasieweerstand (DP\V) ondersoek om die moontlike weerstand teen eksterne beserings en die mate waartoe turgor en dopdikte 'n invloed daarop mag uitoefen, _vas te stel. Daaglikse variasie in DPW het bevestig dat die DPW nie alleen afhanklik is van dopsterkte nie, maar ook van die turgor van die korrel. Doppenetrasieweerstand blyk 'n goeie maatstaf te wees vir die mate waartoe cultivars weerstand hied teen sekere eksterne beserings omdat dit gebaseer is op dopsterkte en turgor van die korrel.

Call number: LD2668 .T4 1986 S64 / Master of Science / Animal Sciences and Industry

Thesis (M.Sc. (Plant Production)) -- University of Limpopo, 2014 / Wild medlar (Vangueria infausta subsp. infausta) is a popular indigenous fruit available and consumed by rural communities in Limpopo Province, South Africa. Inadequate post-harvest practices in indigenous fruit plants including V. infausta fruit forms major constrains in expanding their production. There is scanty information documented on neither objective nor subjective harvesting indices of indigenous fruit plants consumed by locals in sub-Saharan Africa. Thus, the objective of this study was to determine the effect of harvesting time on physico-chemical properties and selected nutritional composition of V. infausta fruit. Fruits were harvested twice, where two harvesting times were regarded as treatments and each tree as replication. The reduction for fruit weight, sugar content and sugar/acid ratio was highly significant (P ≤ 0.05), whereas for average fruit diameter, seed weight, acid ratio and pH content this may imply that the listed parameters are treatment which was non-significant (P ≤ 0.05). The treatment reduced P, K, Mn and Fe by 33%, 18%, 3% and 7%, respectively. On the other hand, treatments had no effect on N and Ca. The reduction of phosphorus was highly significant (P ≤ 0.05), whereas for N, K, Ca, Mn and Fe treatment impact was non-significant (P ≤ 0.05). Similarly, the treatment consistently reduced moisture content and increased dry matter and crude protein of V. infausta by 76%, 300% and 7%, respectively. The reduction of moisture content, increase in dry matter was highly significant (P ≤ 0.05), whereas crude protein treatment impact was non-significant (P ≤ 0.05). The data indicated that the best time to harvest V. infausta fruit was during January when fruits were cosmetically appealing and not wrinkled. This study demonstrated that there was less variation in some measured objective harvesting indices of V. infausta fruit harvested at two harvesting time. More work would be required to do physico-chemical properties and selected mineral elements analysis from wide growth habitat for conclusive recommendations.

Thesis (M. Sc. Agriculture (Soil Science)) -- University of Limpopo, 2016. / Canola (Brassica napus) is an important oil crop which is not well grown in Limpopo Province. Planting date is identified as a critical management decision in canola production for enhanced biological and economic returns as it has direct influence on the growing condition at which the crop is exposed to. The objective of the study was to determine the impact of planting date on growth, grain yield, oil content and economic returns on canola production as a winter crop option in the province. The study was conducted at two climatically diverse locations; the University of Limpopo experimental farm at Syferkuil and an Ofcolaco farmers’ field in 2013 and 2014. Canola was planted at four different dates (April, May, June and July) and (March, April, May) during 2013 and 2014 growing seasons, respectively, in a randomised complete block design (RCBD) under four replications, using AG-Muster cultivar. Weather parameters were obtained from Agricultural Research Council and University of Limpopo experimental farm. Plant parameters measured were days to seedling emergence, flowering and physiological maturity, plant height, number of main and sub branches, dry matter at onset of flowering and crop residues after threshing, number of pods per plant, number of seeds per pod, unshelled and shelled weight, and grain yield. The results revealed that, days to seedling emergence responded significantly (P≤0.01) and (P≤0.05) to planting date at both locations and years except in 2014 at Syferkuil. Plant height was significantly influenced by planting date in 2013 at both locations but in 2014, the effect was significant at maturity and flowering at Syferkuil and Ofcolaco respectively. At Ofcolaco, planting date influenced days to 50% flowering, physiological maturity and plant height in both growing seasons. The influence of planting date on days to flowering and physiological maturity was significant (P≤0.01) at both locations and seasons. Canola dry matter accumulation at flowering responded significantly (P≤ 0.01) to planting date only at Syferkuil in 2013 across seasons and locations whereas residue after seed threshing responded significantly at both locations and seasons. Grain yield was significantly (P≤0.01) influenced by planting dates at all locations and seasons ranging from 292 to 2983 kg ha-1. At Syferkuil, planting canola not later than April resulted in higher grain yield whereas at Ofcolaco, planting between April and May produced the highest grain yield. The number of pods per 2 plant influenced grain yield more than the other yield components studied and regarding weather variables, minimum temperature was found to be most important in influencing growth and grain yield of canola. Oil yield ranged from 155 to 539 kg ha-1 at Syferkuil, in 2013 whilst in 2014, the range was 252 to 614 kg ha-1. At Ofcolaco, significant response of oil yield to planting dates was observed in both seasons. Economic returns at Syferkuil ranged from -R6213.00 to +R2130.00 whereas at Ofcolaco the range was +R793.00 to +R6555.00. The study revealed that Ofcolaco appeared to be better suited for canola production compared to Syferkuil due to higher grain yield and positive economic returns at the former. Keywords: canola; grain yield; oil yield; plant density, planting dates, weather parameters. / The National Research Foundation (NRF) through the Risk and Vulnerability Science Centre (RVSC). VLIR-IUC Programme.

Thesis (MscAgric (Viticulture and Oenology))--University of Stellenbosch, 2007. / A common phenomenon in most South African vineyards, especially in the Western Cape region, is that of within vineyard variation. This variation phenomenon is caused by an array of controllable and non-controllable factors that interact with each other to affect vine vigour. Controllable factors can be managed by the grape grower, while the non-controllable factors have to be managed in the planning process in order not to negatively affect productivity or product quality. The main goal of any grape grower is to optimise vine performance in an attempt to achieve the best possible yield while at the same time allowing vines to optimally ripen grapes towards optimal wine quality. A grape grower has to use every possible means and technique available to him in order to manage his vineyards in such a manner as to achieve this goal. In the past, it was difficult to visualize the extent and distribution of vigour variation in vineyards, but with modern technological improvements in the field of remote sensing, grape growers are able to identify and specify different vigour levels within a vineyard. When remote sensing is applied in a vineyard, the grape grower can identify certain areas that may need more specific attention than others. Consequently, managerial decisions based on detailed information can be made in an attempt to improve the general condition and performance of a vine. Not only can the acquired information be used to plan managerial actions throughout the season, but it can also be used to plan and devise harvest strategies. Some areas in a vineyard may be at a certain point in the ripening process and need to be harvested, while grapes from other areas still need to develop the wanted flavours. One managerial action applied at véraison by some grape growers, is that of crop thinning. Different vigour areas can now be subjected to various crop thinning actions in an attempt to determine the best crop load for a vigour level. With this in mind, two studies were launched to firstly investigate the interaction between vine vigour and harvest dates; and secondly to investigate the interaction between vine vigour and crop load and how their combined interaction might influence a vine’s characteristics, grape composition and wine quality. Vigour variation was firstly identified through multispectral aerial imagery, and then visually verified by visits to the experimental vineyards. The multispectral aerial image was then “orthorectified” in order to produce a classified multispectral image. The image was classified through different colour codes that were assigned to the different vigour levels to clearly distinguish between them. A series of vegetative and reproductive measurements were conducted to try and establish if any correlations could be obtained of the interaction between vine vigour, different harvest dates and crop loads. In order to verify differences in vine vigour, underlying causes were also determined through soil analyses of which chemical analysis, bulk density, porosity, as well as root penetration and distribution were determined. Vegetative measurements that were conducted for both studies indicated good correlations between the different vigour levels and the image classifications. The results also identified the effect that topping (mechanical or manual) had on the main and lateral leaf areas. Reproductive measurements throughout the season, in the form of berry sampling, showed changes in berry composition and accentuated the effects of the different treatments, which could also be confirmed through sensorial analysis of the wines. The results also emphasized the need to not only make use of one of two chemical parameters to identify grape ripeness, but to incorporate a number of parameters, such as sugar, pH and acid levels. From the varying grape chemical characteristics, a wine style can be identified that might carry the approval of the winemaker for the production of a specific type of wine. Soil studies of both vineyards also gave important evidence for the causes of vigour variation. The data collected will hopefully provide grape growers with information that will enable them to make educated decisions concerning grape production and how vigour, in conjunction with different harvest dates and crop loads, will enable them to produce fruit of good quality and, so doing, improve their financial position.

Thesis (M. Sc. (Horticulture)) -- University of Limpopo, 2018 / ‘Hass’ avocado fruit changes skin colour from green to purple and then black during ripening. However, markets importing South African avocado fruit have been complaining about the ‘Hass’ skin colour not changing to purple/black during ripening. Thus, the study aimed to investigate the effect of tree girdling, harvest time and ripening temperature on ‘Hass’ avocado fruit skin colour development during ripening. The mature ‘Hass’ avocado fruit were harvested from girdled and non-girdled trees during early (April), mid- (May) and late (June) harvest times. Upon arrival, in the laboratory fruit were cold stored at 5.5°C for 28 days. After storage, fruit were ripened at 25, 21 and 16°C for 8, 6 and 4 days, respectively. After withdrawal from clod storage fruit were evaluated for skin colour development, ripening and physiological disorders (chilling injury). Fruit from girdled trees showed high maturity (low moisture content) when compared with fruit from non-girdled trees during early and mid-harvest. With respect to skin colour development, the results indicate that skin eye colour development of fruit from girdled and non-girdled trees minimally increased from emerald green (1) to olive green (3) across all harvest times, ripening temperature and ripening duration. However, late season fruit from non-girdled trees improved to purple (4) when ripened at 21°C when compared with fruit from girdled trees. In terms of objective colour, lightness, hue angle and chroma decreased for fruit from girdled and non-girdled trees, across all harvest times, ripening temperature and ripening duration. Lightness and hue angle of fruit from girdled trees were slightly reduced when compared with fruit from non-girdled trees, throughout all harvest times, ripening temperature and duration. Early and mid-season fruit harvested from girdled trees showed rapid decrease of chroma when compared with fruit from non-girdled trees, throughout ripening temperature and x duration. In terms of softening, fruit from girdled trees showed higher firmness loss and ripening percentage within 6 (16°C) and 4 (21 and 25°C) days when compared with fruit from non-girdled trees during early and mid-harvest, whereas, late harvest fruit from girdled trees reached higher ripening percentage and firmness loss within 4 days throughout ripening temperatures. With respect to cold damage, late harvested fruit from girdled trees showed higher external chilling injury when compared with non-girdled trees, throughout ripening temperature. In general, girdling treatment improved fruit maturity, ripening rate and firmness loss. However, the incidence of variable skin colouring of ‘Hass’ avocado fruit during ripening was also prevalent in early harvested fruit from girdled tree, irrespective of ripening temperature. Keywords: girdling, harvest time, physiological disorder, ripening temperature, variable colouring

Thesis (M.Sc. (Horticulture)) --University of Limpopo, 2018 / ‘Hass’ avocado fruit changes skin colour from green to purple and then black during ripening. However, markets importing South African avocado fruit have been complaining about the ‘Hass’ skin colour not changing to purple/black during ripening. Thus, the study aimed to investigate the effect of tree girdling, harvest time and ripening temperature on ‘Hass’ avocado fruit skin colour development during ripening. The mature ‘Hass’ avocado fruit were harvested from girdled and non-girdled trees during early (April), mid- (May) and late (June) harvest times. Upon arrival, in the laboratory fruit were cold stored at 5.5°C for 28 days. After storage, fruit were ripened at 25, 21 and 16°C for 8, 6 and 4 days, respectively. After withdrawal from clod storage fruit were evaluated for skin colour development, ripening and physiological disorders (chilling injury). Fruit from girdled trees showed high maturity (low moisture content) when compared with fruit from non-girdled trees during early and mid-harvest. With respect to skin colour development, the results indicate that skin eye colour development of fruit from girdled and non-girdled trees minimally increased from emerald green (1) to olive green (3) across all harvest times, ripening temperature and ripening duration. However, late season fruit from non-girdled trees improved to purple (4) when ripened at 21°C when compared with fruit from girdled trees. In terms of objective colour, lightness, hue angle and chroma decreased for fruit from girdled and non-girdled trees, across all harvest times, ripening temperature and ripening duration. Lightness and hue angle of fruit from girdled trees were slightly reduced when compared with fruit from non-girdled trees, throughout all harvest times, ripening temperature and duration. Early and mid-season fruit harvested from girdled trees showed rapid decrease of chroma when compared with fruit from non-girdled trees, throughout ripening temperature and x duration. In terms of softening, fruit from girdled trees showed higher firmness loss and ripening percentage within 6 (16°C) and 4 (21 and 25°C) days when compared with fruit from non-girdled trees during early and mid-harvest, whereas, late harvest fruit from girdled trees reached higher ripening percentage and firmness loss within 4 days throughout ripening temperatures. With respect to cold damage, late harvested fruit from girdled trees showed higher external chilling injury when compared with non-girdled trees, throughout ripening temperature. In general, girdling treatment improved fruit maturity, ripening rate and firmness loss. However, the incidence of variable skin colouring of ‘Hass’ avocado fruit during ripening was also prevalent in early harvested fruit from girdled tree, irrespective of ripening temperature. Keywords: girdling, harvest time, physiological disorder, ripening temperature, variable colouring

Made available in DSpace on 2017-07-10T17:37:33Z (GMT). No. of bitstreams: 1 Idiana Marina Dalastra.pdf: 417569 bytes, checksum: 7aadf5ff85c0cf188731924d8a749c19 (MD5) Previous issue date: 2009-12-09 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / In the several options of fruits species with good perspectives for the organic production, it can stand out the fig (Ficus carica L.) as one of the most promising, mainly in relation to production of destined green figs the industrialization, front to possibility of aggregation of values in the final product, in the industrialization process. The objective of this work was to verify the effect of pruning time and number of productive branches on production of the Roxo de Valinhos by production of green figs, in the subtropical region, under organic culture. The experiment using four year-old plants, with spacing 3 x 2 m, in Quatro Pontes-PR (24º35 42 South latitude and 53º59 54 West longitude, altitude of 472 m and Cfa Koppen climate, with annual maximum medium temperature of 28.5ºC and minimum of 16.6ºC). They settled two experiments, with the design utilized was randomized blocks with four blocks and three plants of parcel, and the first related the pruning time: April, May, June, July, August and September; and second related the number of productive branches: 6, 9, 12, 15, 18, 21 and 24. The referring data the phenology of the plants, as well as of the vegetative development and cropping cycles of 2007/2008 were collected. There were yield differences between pruning times; the July and August pruned plants presented higher yields, among the December to February months, with production pick in January. The highest green fig yield (2,949.55 g for plant) and dear productivity (4,916.9 kg for ha) was observed in the treatment which had plants conducted with 18 and 21 productive branches / Dentre as várias opções de espécies frutíferas com boas perspectivas para a produção orgânica, pode-se destacar a figueira (Ficus carica L.) como umas das mais promissoras, principalmente em relação à produção de figos verdes destinados a industrialização, devido à possibilidade de agregação de valores no produto final, no processo de industrialização. O objetivo deste trabalho foi verificar o efeito da época de poda e do número de ramos produtivos sobre a produção da figueira Roxo de Valinhos para a produção de figos verdes, cultivada em condições subtropicais sob cultivo orgânico. Para a realização dos experimentos utilizou-se plantas de quatro anos de idade, com espaçamento 3 x 2 m, localizadas em Quatro Pontes-PR (24º35 42 latitude Sul e 53º59 54 longitude Oeste, altitude de 472 m e clima Cfa Köppen, com temperatura média máxima anual de 28,5ºC e mínima de 16,6ºC). Instalaram-se dois experimentos, em delineamento em blocos ao acaso, com quatro blocos e três plantas úteis por parcela, sendo o primeiro relacionado à época de poda: abril, maio, junho, julho, agosto e setembro; e o segundo com diferentes números de ramos produtivos: 6, 9, 12, 15, 18, 21 e 24. Foram mensurados os dados referentes à fenologia das plantas, bem como o desenvolvimento vegetativo e produção durante o ciclo 2007/2008. Houve diferenças de produção entre as épocas de poda; plantas podadas em julho e agosto apresentaram maiores produções, escalonadas entre os meses de dezembro a fevereiro, com pico de produção em janeiro. A maior produção (2.949,55 g por planta) e produtividade estimada (4.916,9 kg por ha) de figos verdes foram obtidas quando as plantas foram conduzidas com 18 e 21 ramos produtivos