Submitted in fulfillment of the requirements for the Degree of Master of Applied Science in Chemistry, Durban University of Technology, Durban, South Africa, 2016. / This study involves the development of a sensitive electrochemical biosensor for the determination of capsaicin extracted from chilli pepper fruit, based on a novel signal amplification strategy. The study therefore, seeks to provide a sensitive electro-analytical technique to be used for the determination of capsaicin in food and spicy products. Electrochemical measurements using cyclic voltammetry (CV) and differential pulse voltammetry (DPV) modes were utilized in order to understand the redox mechanism of capsaicin and to test the performance of the developed biosensor supported with computational techniques. In this work two different enzymes, Phenylalanine ammonia lyase (PAL) and Glucose oxidase (GOx) were used for electrode modifications respectively. For this purpose three different types of working electrodes namely: glassy carbon electrode (GCE), platinum electrode (Pt-E) and gold electrode (Au-E) were used and their performances were compared. For the first time, the three electrodes were modified with PAL and GOx enzymes on multiwalled carbon nanotubes used in this study and characterized by attenuated total reflectance infrared spectroscopy, transmittance electron microscopy and thermo-gravimetric analysis supported by computational methods. The comparison of the results obtained from the bare and modified platinum electrodes revealed the sensitivity of the developed biosensor with modified electrode having high sensitivity of 0.1863 µg.L-1 and electron transfer rate constant (ks) of 3.02 s-1. To understand the redox mechanism completely, adsorption and ligand-enzyme docking simulations were carried out. Docking studies revealed that capsaicin formed hydrogen bonds with Glutamates (GLU355, GLU541, GLU586), Arginine (ARG) and other amino acids of the hydrophobic channel of the binding sites which facilitated the redox reaction for detection of capsaicin. These results confirm that the PAL enzyme facilitated the electron transfer from the capsaicin ligand, hence improving the biosensing response. Our results suggest potential applications of this methodology for the determination of capsaicin in the food industry. / M

Bibliography: leaves 162-198. This thesis investigates the mechanism(s) involved in the protection of Capsicum seedlings by two isolates of BNR against the damping-off fungus, P.u. sporangiiferum. Emphasis is placed on ecological attributes of the antagonists in relation to the pathogen, in conditions resembling those of the nursery environment for which biological control is intended. It is proposed that competition for resources, such as the host tissues with exudate-rich infection sites and the organic residue in the potting mix, is the principal factor influencing the interactions between P.u. sporangiiferum and BNR. It is also suggested that BNR isolates employ at least three strategies to exert competitive advantage over P.U. sporangiiferum. It is postulated that the ability of BNR to capture and utilise resources, in the presence of a potential competitor, is the principal attribute of these biocontrol agents that brings about a sucessful control of P.u. sporangiiferum in nursery potting mix.

Pepper plants (Capsicum annuum L.) were grown in field and a greenhouse in Arizona to determine the effects of water stress, root temperature, and exogenously applied growth regulators on cytokinin production and the resulting growth. Research showed that vegetative plants were significantly higher in cytokinin activity and growth parameters than fruiting plants. Also, in root-pruned fruiting plants, cytokinin activity was less than that of intact fruiting plants. In vegetative plants, the competition between removed sinks and the rest of the shoot was reduced and, hence, more cytokinin came from the roots to the shoots. Besides, additional carbohydrates were available and recycled to the roots. In respect to temperature effect, elevating temperature from 15 to 30°C had a pronounced effect of increasing the growth rate and cytokinin activity. The measured parameters declined when temperature exceeded 30°C. Temperatures between 25 and 30°C were found to be optimum. Under experimental conditions, growth regulators (Cytex® and Burst®) applied to the soil or foliage had no significant effect on growth rates or cytokinin activity in roots. Also, applying Burst® or kinetin to the nutrient medium had inconsistent and statistically nonsignificant effects on photosynthesis and transpiration.

No description available.

No description available.

Pepper (Capsicum annuum L.) is an important vegetable crop grown and consumed worldwide. Potato virus Y (PVY) is a globally economically important pathogen which significantly reduces the yield and quality of cultivated pepper. The virus is considered as a major limiting factor to the economic production of pepper in the province of KwaZulu-Natal (KZN) in the Republic of South Africa (RSA). Many applied practices to control the spread of PVY are ineffective to mitigate the losses incurred by many farming communities across the KZN province. Therefore, the objectives of this study was to determine the full genome sequence of a PVY isolate from KZN, to identify resistance alleles in commercially available pepper varieties in KZN and to develop a pepper hybrid variety with resistance to PVY using a molecular breeding strategy The first part of the study was conducted to determine the first full genome sequence of a PVY isolate (JVW-186) infecting pepper from KZN. The complete genome sequence of JVW-186 was assembled from overlapping RT-PCR clones using MEGA 5 software. Individual ORFs were identified using the nucleotide data base NCBI and aligned using CLUSTALW. RDP4 software was used to identify recombination junctions in the sequence alignment of JVW-186. CLC Main Workbench 6 software was used to determine the nucleotide sequence similarity of recombinant and non-recombinant fragments of JVW-186 in conjunction with ten PVY parental isolates. Based on sequence data, virus morphology and the coat protein size as determined by SDS-PAGE analysis, the identity of the isolate JVW-186 was confirmed as PVY. Phylogenetic trees were constructed from all recombinant and non-recombinant segments of the sequence by the maximum likelihood method using MEGA 5 software. The full length sequence of JVW-186 consisted of 9700bp. Two ORF’s were identified at position 186 and 2915 of the sequence alignment encoding the viral polyprotein and the frameshift translated protein P3N-PIPO, respectively. RDP4 software confirmed two recombination breakpoints at position 343 and 9308 of the sequence resulting in four segments of the genome. At each recombination event, a 1021-bp fragment at the 5’ end in the region of the P1/HC-Pro protein and a 392-bp fragment in the region of the coat protein shared a high sequence similarity of 91.8 % and 98.89 % to the potato borne PVYC parental isolate PRI-509 and the PVYO parental isolate SASA-110 respectively. The non-recombinant fragment 1 clustered within the C clade of PVY isolates; however the large 7942-bp fragment 3 did not cluster within any of the clades although it shared > 80% nucleotide sequence similarity to other PVY isolates used in this study. Our results suggest that isolate JVW-186 is a novel recombinant strain of PVY that could have evolved due to the dynamics of selection. The second part of the study aimed to evaluate different pepper lines for resistance to PVY. Two recessive alleles (pvr21 and pvr22) located on the pvr2-elF4E locus are known to confer resistance to the virus. To this end, six pepper lines were challenged with PVY infected Nicotiana tabacum cv. Xanthi leaf material using mechanical inoculation under greenhouse conditions. Each line was assessed for resistance to PVY by visual screening for disease severity and quantitative enzyme linked immunosorbent assay (ELISA) for virus load. Pepper lines were further characterized using tetra-primer ARMS-PCR (amplification refractory mutation system polymerase chain reaction) to identify and differentiate the presence of homozygous/heterozygous resistance alleles that confer PVY resistance. Evaluations revealed two resistant pepper lines (Double Up and Cecelia) and varying levels of susceptibility in the other four pepper lines challenged with PVY. The most susceptible pepper line was Benno, although high levels of susceptibility were observed in three other lines (IP, Mantenga and Excellence). The pvr2+ allele was positively identified in all the susceptible pepper lines using the T200A tetra-primer which confirms that the presence of this allele is dominant for PVY susceptibility. Double Up and Cecelia were genotyped homozygous pvr21/pvr21 and pvr22/pvr22 respectively, and remained asymptomatic throughout the trial which indicates that these alleles confer resistance to the isolate of PVY used in this study. The information generated in this study can be incorporated into breeding programs intended to control PVY on pepper in KZN. The final part of the study focused on the development of resistant varieties as the best alternative to manage PVY diseases on pepper. Homozygous F2 pepper lines were developed from local germplasm carrying PVY resistance genes (pvr21 and pvr22) using marker assisted selection (MAS). The F1 progeny was obtained by crossing a homozygous pvr21 (resistant) ‘Double Up’ cultivar with a heterozygous susceptible (pvr2+/pvr22) ‘Benno’ cultivar. F1 and F2 generations were assessed for the presence of PVY resistance/susceptibility alleles (pvr2+/pvr21/pvr22) at the pvr2-elF4e locus using the tetra primer amplification refractory mutation system – polymerase chain reaction (ARMS-PCR) procedure. Negative selection was carried out using the tetra-primer T200A marker to detect the pvr2+ (susceptible) allele. All F1 progeny displaying the pvr2+ allele were eliminated from further study. All 302 plants belonging to 29 F2 families expressing homozygous recessive traits were tested via mechanical inoculation for their response to PVY infection and resistance to PVY was confirmed in all selected families based on symptomatology in greenhouse house screens using double antibody sandwich enzyme linked immunosorbent assay (DAS-ELISA). These results show that ARMS-PCR can be used to successfully screen pepper genotypes for alleles that confer PVY resistance thereby contributing to the improvement of pepper production using molecular breeding approaches. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2013.

The main objective of this work is to investigate whether the time required to dry red peppers in the diffusion controlled period can be reduced. For this purpose, the possibility of microwave drying in this period was studied. As comparison parameters the drying rates and color of the products were selected. The conventional drying was conducted under constant external drying conditions with air at 60 0C and 3.5 % RH and 1.0 m/s velocity in a batch dryer. For the microwave drying a domestic microwave oven with three power levels, 286, 397 and 560 W was used. Pre-experiments were done to obtain an insight on the possibility of moisture distribution within the structure of the red peppers and electrical field distribution inside the oven cavity. The non-uniformity due to the latter effect was tried to be overcome by designing and installing a six blade impeller into the bed having the symmetrical pair of blades fixed at three levels. Samples for the microwave drying experiments were prepared by drying the peppers from approximately 90% of moisture to 20% in 7 hours in the conventional dryer at 600C and then cutting them into pieces about 1x1 cm. Thus prepared samples were dried further in the microwave oven to 14% moisture content without and with the agitator. To compare the results, the effective diffusivity coefficients were calculated for all of the methods and parameters to enable the aimed comparison. These indicated that by using microwave drying, the drying time can be reduced by about 120 times. Further, by mixing the uniformity of drying and the drying rate could be improved. Considering color of the product, there was no significant difference with respect to the fresh samples after all operations.

Bibliography: leaves 162-198. / x, 198 leaves, [12] leaves of plates : ill. [some col.] ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / This thesis investigates the mechanism(s) involved in the protection of Capsicum seedlings by two isolates of BNR against the damping-off fungus, P.u. sporangiiferum. Emphasis is placed on ecological attributes of the antagonists in relation to the pathogen, in conditions resembling those of the nursery environment for which biological control is intended. It is proposed that competition for resources, such as the host tissues with exudate-rich infection sites and the organic residue in the potting mix, is the principal factor influencing the interactions between P.u. sporangiiferum and BNR. It is also suggested that BNR isolates employ at least three strategies to exert competitive advantage over P.U. sporangiiferum. It is postulated that the ability of BNR to capture and utilise resources, in the presence of a potential competitor, is the principal attribute of these biocontrol agents that brings about a sucessful control of P.u. sporangiiferum in nursery potting mix. / Thesis (Ph.D.)--University of Adelaide, Dept. of Crop Protection, 1997

The vermicomposting of coffee grounds shows great promise for urban areas and university campuses. Several studies have examined using coffee grounds as a substrate for vermicomposting, however, little is known about its effect on plant growth, yield and quality. Therefore, two studies were conducted to assess these effects on greenhouse spinach and field grown bell peppers. Coffee vermicompost (VC) was utilized in a greenhouse spinach study over two spring growing seasons (2011 and 2012). Coffee VC was added to a 1:1:1 (peat, soil, sand) medium by volume (0, 25, 50 and 75%) in 4.5 L clay pots and seeded with `Bloomsdale Longstanding' spinach (Spinacia oleracea). Growth parameters evaluated were fresh leaf weight (FLW), leaf area (LA), spinach plant height, number of leaves, fresh leaf ascorbic acid (AA) and dry leaf nitrate (DLN). In 2011, the highest FLW, LA, number of leaves, AA and nitrate content were seen at the 75% VC application rate. Many parameters were correlated: The FLW and the VC application rate (r=0.41, P<0.0001); the AA content in leaves and the VC application rate (r=0.60, P<0.0001); and the AA and nitrate content in leaves (r=0.45, P=0.011). In 2012, the greatest FLW, height and number of leaves were observed at the 50% VC application rate; the highest nitrate content at 75% VC application rate, with no difference in AA content. A field study was conducted over three seasons (2009–-2011) to compare four treatments (coffee VC, dairy compost, standard fertility (SFT) and no treatment) for their effects on growth, yield, and AA content of bell peppers. Coffee VC and dairy compost were applied to beds at the rate of 22 t/ha and SFT was applied as 212 kg/ha 12:12:12 (N:P:K). Parameters evaluated were total number and weight of marketable and cull (unmarketable) pepper fruits, plant height, leaf chlorophyll index, and fresh fruit AA content. There were no differences detected for pepper fruit yields or AA content, however, plant height and chlorophyll index were greater for the VC and SFT treatments than for the compost and control treatments. These results indicated that coffee VC can improve the yield of greenhouse spinach and that the AA content does not decrease with higher VC application rates, even as nitrate content increases. Results of the bell pepper field study indicated that the coffee VC treatment produces similar growth, yield and AA content as SFT.

Made available in DSpace on 2014-12-02T11:16:48Z (GMT). No. of bitstreams: 0 Previous issue date: 2013-11-08Bitstream added on 2014-12-02T11:21:32Z : No. of bitstreams: 1 000793445_20161108.pdf: 44300 bytes, checksum: 1104528202f640b31f6181c040666115 (MD5) Bitstreams deleted on 2016-11-16T11:41:25Z: 000793445_20161108.pdf,. Added 1 bitstream(s) on 2016-11-16T12:24:07Z : No. of bitstreams: 1 000793445.pdf: 794571 bytes, checksum: b0bf9d63d28d7da0a2034c160d31312e (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / O presente trabalho teve como objetivos avaliar o efeito antioxidante de extratos de pimentas vermelhas in natura do gênero Capsicum e medir a estabilidade oxidativa do óleo de soja adicionado do extrato de pimenta; além de avaliar a retenção dos tocoferóis, naturalmente presentes no óleo de soja, durante os testes de estocagem acelerada em estufa e em temperatura ambiente. Nos extratos hidroalcóolicos liofilizados das pimentas Malagueta, Cumari, Bode e Dedo-de-moça, foram avaliados a atividade antioxidante por meio dos sistemas DPPH· (2,2-diphenyl-1- picrylhydrazyl), β-caroteno/ácido linoleico, FRAP (Ferric Reducing Antioxidant Power) e ABTS·+ (2,2- azino-bis-3- ethylbenzo-thiazoline-6-sulfonic acid), os teores de compostos fenólicos, carotenoides totais e ácido ascórbico. Os tratamentos: Controle (óleo de soja), TBHQ100 (óleo de soja + 100 mg/kg de TBHQ), TBHQ200 (óleo de soja + 200 mg/kg de TBHQ), BHA100 (óleo de soja + 100 mg/kg de BHA), BHA200 (óleo de soja + 200 mg/kg de BHA), Extrato100 (óleo de soja + 100 mg/kg de compostos fenólicos totais de pimenta Malagueta) e Extrato200 (óleo de soja + 200 mg/kg de compostos fenólicos totais de pimenta Malagueta), foram submetidos ao teste acelerado em estufa (60ºC/20 dias) e ao teste em temperatura ambiente (28ºC/9 meses). Os tratamentos foram analisados por meio das medidas de índice de peróxidos, dienos conjugados, índice de estabilidade oxidativa, teores de tocoferóis e ganho de massa (60ºC/30 dias). Os resultados obtidos das determinações analíticas foram submetidos à análise de variância e as diferenças entre as médias foram testadas a 5% de probabilidade pelo teste de Tukey. As pimentas são boas fontes de ácido ascórbico, carotenoides e compostos fenólicos. Estes compostos conferem às pimentas propriedades antioxidantes, mesmo que sejam submetidos a processos de estresse oxidativo. Os extratos da pimenta Malagueta adicionados ao óleo de soja como ... / This study aimed to evaluate the antioxidant capacity of extracts from red peppers of the genus Capsicum in nature and measure the oxidative stability of soybean oil added of pepper extract, as well as evaluating the resistance of tocopherols naturally present in soybean oil during the accelerated storage tests in stove and at room temperature. In the lyophilized hydroalcoholic extracts of Malagueta, Cumari, Bode, and Dedo-de-moça, the antioxidant activity, by means of antioxidant systems DPPH· (2,2-diphenyl-1-picrylhydrazyl), β-carotene/linoleic acid, FRAP (Ferric Reducing Antioxidant Power), and ABTS·+ (radical 2,2-azinobis-3-ethylbenzothiazoline-6- sulfonic acid), and also the levels of phenolics, total carotenoids, and ascorbic acid were evaluated. Treatments: Control (soybean oil-free antioxidants), TBHQ100 (soybean oil + 100 mg/ kg TBHQ), TBHQ200 (soybean oil + 200 mg/kg TBHQ), BHA100 (soybean oil + 100 mg/kg BHA), BHA200 (soybean oil + 200 mg/kg BHA), Extract100 (soybean oil + 100 mg/kg of total phenolic compounds of Malagueta), and Extract200 (soybean oil + 200 mg/kg of total phenolic compounds of Malagueta) were subjected to the accelerated storage test (60°C/20 days) and to the test at room temperature (28°C/9 months). The treatments were analyzed by measuring the peroxide value, conjugated dienes, oxidative stability index, levels of tocopherols, and mass gain (60ºC/30 days). The results of analytical determinations were subjected to analysis of variance and differences between means were tested at 5% probability by Tukey test. The peppers are good sources of ascorbic acid, carotenoids, and phenolic compounds. These compounds provide the peppers with antioxidant properties, even if they are subjected to oxidative stress conditions. Chilli pepper extracts added to soybean oil as natural antioxidants were capable of reducing the changes suffered by soybean oil during the storage process, thus being able to be natural ...