Tesi sul tema "Cultivated"

Pesticides are widely used for preventing crop losses due to pest attack. In Bangladesh, the food safety and health of farmers are being compromised as a result of poor regulation concerning usage of pesticides in food production. The aim of this study was to identify and quantify pesticides applied on cucumber crops in Bangladesh. A method for extraction and clean-up was developed to allow the quantification of four pesticides by GC-ECD in vegetable samples, specifically cucumber. The accuracy of the method was validated using recovery and its precision by studying the standard deviation and relative standard deviation. Analysis of cucumber samples obtained in the field showed no traces of the target pesticides. The results indicate that different types of chemicals are used on the examined crops. It is also believed that the growth habit of cucumber may affect the exposure to pesticides. To overcome the health hazards, restrictions regarding the types and quantities of chemicals used on the fields need to be implemented. Further studies would benefit from being executed in a controlled environment, and monitoring of which substances that are applied at which amounts.

The objective of our design was to create a chemical plant that uses cultivated algae grown on site in order to produce a biofuel as an alternative energy source. Currently there is a push for sustainable energy sources and biologically produced fuels are attractive due to their near net-zero carbon emissions. Algae provides a valuable source of energy due to its growth rate and sustainability. Chemical engineering principles were utilized in design; a supercritical carbon dioxide extractor for the triglycerides in the algae cells, base catalyzed transesterification reaction in continuously stirred reactors in series and separation processes at the end in order to produce a high grade biofuel for consumer applications. Emphasis on environmental consideration also went into the design, such as the use of carbon dioxide for both the growth of the algae and solid extraction process and methanol used for the transesterification and liquid extraction, allowing for easy recycle and further reducing the environmental footprint the product fuel will have.

Yield losses due to wild species are relevant for a variety of cropping systems worldwide, e.g., in the case of rice weeds they can reach 60%. However, in the broader sense, wild species may also have positive effects on cropping systems for their capability to provide environmental benefits. In fact, they are fundamental to maintain high levels of biodiversity and, in the context of grassland communities, they are crucial for the provision of ecosystem services like those involved with pollination and recreational experiences. A quantitative understanding of the complex and dynamic interactions among species within agro-environmental systems is thus crucial to better analyze, for instance, the possible effects of climate change on community dynamics and to timely define effective adaptation strategies. In this context, the aim of this thesis was the development of new models for the simulation of the interaction between cultivated and wild species. Biophysical models are powerful tools to analyze the interactions between plants and environmental variables as well as to optimize crop management. However, one of their main weakness is the lack of algorithms for simulating the interactions between cultivated and wild species. The few examples available that consider these interactions are mainly related to fungal pathogens, whereas approaches considering weeds, insects and multi-species plant communities are extremely rare and insufficiently validated. To fill this gap, this PhD Thesis focused on the modelling of three categories of communities of increasing complexity: crop-weed (two plant species), grasslands (multi-species plant communities) and crop-insect-insect predators (different kingdoms). For the three categories, agroecosystems of worldwide importance were identified as case studies: paddy rice (chapter 2), grasslands (chapter 3 and 4) and olive trees (chapter 5). In particular, in chapter 2 a new model was developed for simulating the interaction between rice and two weeds (barnyardgrass and red rice); chapter 3 and 4 are focused on the extension of a model for the simulation of plant community dynamics in the context of mountain grassland systems, with case studies in temporary grasslands in the Apennine and in natural pastures in the Alps. The third chapter, in particular, focuses on the definition of strategies for adapting 9 grasslands management to climate change by explicitly considering their floristic composition, whereas the fourth chapter presents initial results on the effects of grazing and climate change on the productivity and floristic composition of pasture communities. Chapter 5 shows a new model of interactions among olive trees, the olive fruit fly (Bactrocera oleae (Rossi, 1790)) and its predators, whereas chapter 6 refers to the general conclusions of the researches carried out in this PhD Thesis. Although the new models developed in this work are process-based to reflect the complexity of interactions occurring in agroecosystems, they assume simplified descriptions of biophysical processes through a limited number of parameters to make them usable in operational contexts.

Alimentar a la futura población en crecimiento en un contexto de cambio climático exige nuevos enfoques y herramientas de mejora genética para desarrollar nuevas variedades de cultivos que sean resilientes y eficientes en el uso de los recursos. Entre las hortalizas, la berenjena (Solanum melongena) es reconocida como un cultivo importante y como tal está incluida en el Anexo 1 del Tratado Internacional sobre los Recursos Fitogenéticos para la Alimentación y la Agricultura, que incluye 34 cultivos considerados como los más relevantes para la humanidad. Antes del inicio de esta tesis, se disponía de pocas herramientas genéticas y genómicas para la mejora genética de la berenjena, las cuales se revisan en un capítulo introductorio. Asimismo, hemos reconocido la importancia de los parientes silvestres de la berenjena, que apenas se han utilizado en la mejora genética de la misma. A este respecto, para hacer un uso más eficiente de los parientes silvestres en la mejora genética, propusimos un enfoque ambicioso, llamado "introgressiomics", que consiste en un desarrollo sistemático y masivo de materiales que lleven introgresiones de parientes silvestres (CWR), los cuales generalmente son una fuente inexplorada e desaprovechada de variación genética. Los trabajos realizados en esta tesis están relacionados con la aplicación de este enfoque a la berenjena. En este marco, los objetivos generales de la tesis son el desarrollo de la información y herramientas genéticas y genómicas en el acervo genético de la berenjena, utilizando un enfoque multidisciplinario y multifacético para la mejora genética en el desarrollo de nuevas variedades mejoradas y resistentes usando especies relacionadas como fuente de variación. Concretamente, en el primer capítulo de esta tesis, secuenciamos el transcriptoma de dos especies relacionadas con la berenjena, la silvestre Solanum incanum y la especie cultivada africana S. aethiopicum, que tienen un gran interés en la mejora genética de la berenjena. Los transcriptomas se ensamblaron en 83,905 y 87,084 unigenes para S. incanum y S. aethiopicum respectivamente, los cuales fueron extensivamente anotados estructuralmente y funcionalmente. La busqueda de variantes alélicas identificó decenas de miles de polimorfismos intraespecíficos e interespecíficos, así como alrededor de un millar de SSRs en cada especie. En el segundo capítulo, un subconjunto de esos marcadores (11 SSRs y 35 SNPs) se analizaron para confirmar su utilidad para la huella genética, la evaluación de la diversidad y el establecimiento de relaciones entre las berenjenas cultivadas (común, escarlata y gboma). Observamos que los SSRs y los SNPs proporcionaron resultados diferentes en el establecimiento de las relaciones, lo que sugiere que cada tipo de marcador muestreó diferentes niveles de variación genética. Sin embargo, aunque ambos marcadores proporcionaron un nivel similar de información, los SNPs parecen proporcionar una mejor resolución que los SSRs para materiales filogenéticamente más distantes. En el tercer capítulo, para ampliar la estimación de la diversidad genética y las relaciones genéticas entre y dentro de las especies silvestres y cultivadas pertenecientes al complejo berenjena, realizamos un genotipado masivo, mediante un enfoque de genotipado por secuenciación, de 76 accesiones pertenecientes a 17 especies del acervo genético primario, secundario y terciario de la berenjena común. De los 75,399 sitios polimórficos identificados, 12,859 se asociaron a regiones CDS y se usaron para establecer una evaluación exhaustiva y detallada de la diversidad alélica natural y las relaciones genéticas en el acervo genético de la berenjena utilizando tres enfoques diferentes (estructura jerárquica de la población, dendrograma basado en UPGMA y análisis de PCoA). En el cuatro capítulo, desarrollamos un mapa genético interespecífico entre S. incanum y S. melongena, vinculado a otros
Feeding the future burgeoning population in a climate change scenario demands new breeding approaches and tools to develop new resource-efficient and resilient crop varieties. Among vegetable crops, eggplant (Solanum melongena) is recognized as an important food crop and as such is included in the Annex 1 of the International Treaty on Plant Genetic Resources for Food and Agriculture, which includes 34 crops considered as most relevant for mankind. Before the start of this thesis, few genetic and genomic tools and resources for eggplant breeding, which are reviewed in an introductory chapter, were available. We have recognized the importance of wild eggplant relatives, which have been barely used in eggplant breeding. In this respect, in order to make a more efficient use of wild relatives in plant breeding, we proposed an ambitious approach, called "introgressiomics", consisting of a systematic and massive development of materials carrying introgressions from crop wild relatives (CWRs), which usually are an unexplored and unexploited source of genetic variation for breeding traits. The works done in this thesis are related to the application of the introgressiomics approach to eggplant. In this framework, the general objectives of the thesis are the development of genetic and genomic information and tools in eggplant genepool, using a multidisciplinary and multi-pronged approach to assist eggplant breeding in the development of new improved and resilient varieties using eggplant relatives as a source of variation. Specifically, in the first chapter of this thesis, we sequenced the transcriptome of two eggplant related species, the wild Solanum incanum and the cultivated S. aethiopicum, that have a great interest in eggplant breeding. The transcriptomes were assembled in 83,905 and 87,084 unigenes for S. incanum and S. aethiopicum respectively, which were extensively structurally and functionally annotated. The variant call analysis identified tens of thousands intraspecific and interspecific polymorphisms, as well as around a thousand of SSRs in each species. In the second chapter, a subset of those markers (11 SSRs and 35 SNPs) was tested for confirming their usefulness for genetic fingerprinting, diversity evaluation and the establishment of relationships in cultivated eggplant (common, scarlet and gboma) genepools. We observed that SSRs and SNPs provided different results in the establishment of the relationships, suggesting that each marker type sampled different levels of genetic variation. However, although both markers provided a similar level of information, SNPs seem to provide a better resolution than SSRs for materials phylogenetically more distant. In the third chapter, in order to broaden the estimation of the genetic diversity and genetic relationships among and within wild and cultivated species belonging to eggplant complexes, we performed a massive genotyping, by a genotype-by-sequencing approach, of 76 accessions belonging to 17 species from the primary, secondary and tertiary genepool of common eggplant. Out of 75,399 polymorphic sites identified, 12,859 were associated to CDS regions and used to establish an exhaustive and detailed evaluation of the natural allelic diversity and genetic relationships in eggplant genepool using three different approaches (hierarchical population structure, UPGMA-based dendrogram, and PCoA analysis). In the four chapter, we developed an interspecific genetic map between S. incanum and S. melongena, linked to four previous eggplant maps and to one tomato map. A total of 243 molecular markers were successfully mapped consisting of 42 COSII, 99 SSRs, 88 AFLPs, 9 CAPS, 4 SNPs and one morphological polymorphic markers encompassed 1085 cM distributed in 12 linkage groups. Based on the syntheny with tomato, the candidate genes involved in the core chlorogenic acid synthesis pathway in eggplant (PAL, C4H, 4CL, HCT, C3¿H, HQT), five polyphenol oxidase genes (PPO1, PPO2, PPO3, PP
Alimentar la futura població en creixement en un context de canvi climàtic exigeix nous enfocaments i eines de millora genètica per desenvolupar noves varietats de cultius que siguin resilients i eficients en l'ús dels recursos. Entre les hortalisses, l'albergínia (Solanum melongena) és reconeguda com un cultiu important i com a tal està inclosa en l'Annex 1 del Tractat Internacional sobre els Recursos Fitogenètics per a l'Alimentació i l'Agricultura, que inclou 34 cultius considerats com els més rellevants per a la humanitat. Abans de l'inici d'aquesta tesi, es disposava de poques eines genètiques i genòmiques per a la millora genètica de l'albergínia, les quals es revisen en un capítol introductori. Així mateix, hem reconegut la importància dels parents silvestres de l'albergínia, que tot just s'han utilitzat en la millora genètica de la mateixa. Referent a això, per fer un ús més eficient dels parents silvestres a la millora genètica, vam proposar un enfocament ambiciós, anomenat "introgressiomics", que consisteix en un desenvolupament sistemàtic i massiu de materials que portin introgresions de parents silvestres (CWR), els quals generalment són una font inexplorada i desaprofitada de variació genètica. Els treballs realitzats en aquesta tesi estan relacionats amb l'aplicació d'aquest enfocament a l'albergínia. En aquest marc, els objectius generals de la tesi són el desenvolupament de la informació i eines genètiques i genòmiques en el patrimoni genètic de l'albergínia, utilitzant un enfocament multidisciplinari i multifacètic per a la millora genètica en el desenvolupament de noves varietats millorades i resistents emprent spècies relacionades com a font de variació. Concretament, en el primer capítol d'aquesta tesi, seqüenciem el transcriptoma de dues espècies relacionades amb l'albergínia, la silvestre Solanum incanum i l'espècie cultivada africana S. aethiopicum, que tenen un gran interès en la millora genètica de l'albergínia. Els transcriptomes s'ensamblaren en 83,905 i 87,084 unigenes per S. incanum i S. aethiopicum respectivament, els quals van ser extensivament anotats estructuralment i funcionalment. La recerca de variants al·lèliques va identificar desenes de milers de polimorfismes intraespecífics i interespecífics, així com al voltant d'un miler de SSRs en cada espècie. En el segon capítol, un subconjunt d'aquests marcadors (11 SSRs i 35 SNPs) es van analitzar per confirmar la seva utilitat per l'empremta genètica, l'avaluació de la diversitat i l'establiment de relacions entre les albergínies conreades (comú, escarlata i gboma). Observem que els SSRs i els SNPs van proporcionar resultats diferents en l'establiment de les relacions, el que suggereix que cada tipus de marcador va mostrejar diferents nivells de variació genètica. No obstant això, encara que tots dos marcadors van proporcionar un nivell similar d'informació, els SNPs semblen proporcionar una millor resolució que els SSRs per materials filogenèticament més distants. En el tercer capítol, per a ampliar l'estimació de la diversitat genètica i les relacions genètiques entre i dins de les espècies silvestres i conreades pertanyents al complex albergínia, vam realitzar un genotipat massiu, mitjançant un enfocament de genotipat per seqüenciació, de 76 accessions pertanyents a 17 espècies del patrimoni genètic primari, secundari i terciari de l'albergínia comuna. Dels 75,399 llocs polimòrfics identificats, 12,859 es van associar a regions CDS i es van usar per a establir una avaluació exhaustiva i detallada de la diversitat al·lèlica natural i les relacions genètiques en el patrimoni genètic de l'albergínia utilitzant tres enfocaments diferents (estructura jeràrquica de la població, dendrograma basat en UPGMA i anàlisi de PCoA). En el quart capítol, desenvolupem un mapa genètic interespecífic entre S. incanum i S. melongena, vinculat a altres quatre mapes anterior
Gramazio, P. (2018). GENETICS AND GENOMICS OF CULTIVATED EGGPLANTS AND WILD RELATIVES [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/104605
TESIS

This thesis investigates the ecology of the eider Somateria mollissima in the sealochs of Western Scotland with particular reference to their impact on mussel Mytilus edulis farms. The numbers of eiders within sealochs showed seasonal variations with numbers increasing over February and March to reach a peak in April for all years. A summer decline in numbers was followed by an increase in the early autumn of all study years. Numbers then declined in lochs during the late autumn and early winter periods - a time when numbers in the Clyde estuary showed a corresponding increase. Mussel farms are now present in many sealochs along the West coast of Scotland. Farming is by suspended cultivation using either long-lines or raft flotation. Farms hold a concentrated supply of mussels which are within the size range normally consumed by Eiders. Cultivated mussels are thinner shelled and have a greater flesh content than similar sized individuals from adjacent intertidal populations. Peak numbers of Eiders at farms tended to increase with successive years of cultivation on site. Numbers fluctuated seasonally with large numbers present at farms in spring and autumn of most years. One farm on Loch Etive did, however, have a peak in Eider attendance during the summer. Spring flocks at farms tended to consist mostly of adults, while autumnal flocks were predominantly made up of juvenile birds. There was an excess of males in spring flocks at farms and both sexes arrived and departed simultaneously. A turnover of individuals was seen to take place at farms, with successive groups of birds moving through, giving rise to peaks and troughs in attendance over short periods of time. No definite feeding routine by birds at farms was apparent. The dive duration of birds feeding at suspended ropes decreased when they were scared as did the inter-dive period. The number of dives per feeding bout was seen to alter on sane occasions when birds were scared, scared adults spent less time loafing near ropes than did unscared adults, rather, all their time near ropes was spent actively feeding. Damage to ropes was approximately 2.6 kg of mussels per bird day. It is not inferred that this quantity was actually consumed by the birds but was removed from the ropes by their actions. Damage was visible as ropes completely or partly stripped or where selective removal of particular sizes of mussel had occurred. Plastic fringes placed around rafts were seen to be a useful short-term protective technique. Where alternative food was available then the value of fringes protecting stock was enhanced. Netting was also seen to be a useful protective technique and when placed around long-lines or rafts it may reduce the profitability of feeding at farms to birds by increasing their dive duration necessary to reach the mussel stock. Trials with horizontal and vertical netting around ropes led to a decrease in predation but did not completely eliminate feeding by Eiders at one study raft. The protection strategy enployed on farms must consider the number of birds feeding at the ropes and their pattern of attendance (turnover). Scaring activities and the use of physical barriers could then be pulsed to coincide with periods of maximum likelihood of damage occurring. Farm type and size is also important in protection, with raft based units likely to be easier to protect than long-lines. Similarly, larger farms may be more cost-effective to protect than smaller units.

Les sols sableux peuvent constituer une réserve potentielle de sols cultivables mais leur mise en valeur entraîne toujours des dégradations de la structure et une baisse du potentiel agricole. Une dégradation très fréquente est l’affaissement des couches labourées sous l’action de la pluie, ou slumping. Notre objectif était d’identifier les mécanismes et les facteurs déterminants du slumping afin de proposer des techniques de prévention. L’étude a été conduite sous pluies naturelles (au champ) et simulées (au laboratoire). Au champ, la cinétique d’évolution des caractéristiques hydriques et physiques du sol a été suivie après un labour à 20 ou à 40 cm de profondeur, dans un sol sableux tropical Thaïlande. Au laboratoire, un sol cultivé modèle a été élaboré dans un cylindre (h et Ø = 20 cm) à partir i) du sol prélevé dans le champ expérimental, ii) de la fraction sable (> 50 μm) extraite de ce même sol. Les sols modèles ont subi des pluies d’intensité variable (de 20 à 120 mm/h) après mise en place sur une table à succion (20 à 90 hPa). Le slumping se produit lorsque deux conditions sont réunies: (1) l’eau doit atteindre un potentiel proche de 0 hPa ce qui réduit la cohésion et aboutit à un équilibre fragile du sol comme décrit par la physique des milieux granulaires; (2) ce potentiel doit être maintenu assez longtemps pour qu’une instabilité se produise et entraine une brusque et importante diminution de la cohésion, donc l’effondrement du matériau. Si la fraction fine (<50 μm) est retirée du sol, aucun effondrement n’est observé, démontrant l’importance de cette fraction limonoargileuse, pourtant minoritaire (<10-15 % en masse), dans l’instabilisation et le slumping. La prévention du slumping et la gestion des sols sableux sont discutées en guise de conclusion
The sandy soil can serve as a potential reserve for cultivation. However, they are often considered as marginal because prone to have low productivity and problems of structure degradation. One of the degradations is compaction caused by rainfall or irrigation, which is called slumping. Our objective is to identify the processes and factors that affect slumping. The study had been done under natural conditions (field) and simulated conditions (laboratory) respectively. In the field, a tropical sandy soil in Thailand was selected. After 20 cm and 40 cm depth tillage, the dynamic of hydraulic and physical characteristics were measured. In laboratory, a cultivated soil model was build in a cylinder (height and diameter was 20 cm). We used two materials: 1) the original soil from the experiment field site, and 2) the sand fraction (> 50 μm) extracted from this soil. These model soils were submitted to rainfalls with different intensity (20 to 120 mm h-1), combined with different suction (20 to 90 hPa) on a suction table which can support the cylinder. The slumping for soil happens when two conditions were met: 1) the water potential reached a threshold value near 0 hPa. In this value, the soil cohesion decreased and a fragile equilibrium conditions were reached according to granular material theory; 2) the potential value was kept long enough and the cohesion continue decrease until they can no more support the equilibrium, so slumping happens. Surprisingly, in our treatment, when the fine particles (<50 μm) were taken out from the soil, no slumping was observed. This demonstrates the particles of clay and silt are very important to soil stability, even their content were very low as less than 10 percent. The possible ways to prevent slumping and management of sandy soils are also discussed

As the global population rises, the demand for food increases which underscores a need for improvement in food security. Disease pressures are a major concern surrounding sustainable agriculture. Static crop populations, containing little to no genetic diversity, are vulnerable to diverse pathogen populations. Wild relatives of crop plants are a reservoir for new disease resistance traits that can be introgressed into cultivated crops. The identification of novel disease resistance is of paramount importance because pathogen co-evolution is not only defeating current resistance genes (R genes) but chemical controls as well. Phytophthora sojae (P. sojae), the causal agent of Phytophthora root and stem rot disease, reduces soybean harvests worldwide. We developed an approach to screen for new R genes that recognize core effectors from P. sojae. We expect R genes identified by these screens to be durable because P. sojae requires core effectors for virulence. We utilized effector-based screening to probe Glycine soja germplasm with core RXLR effectors from P. sojae to search for novel R genes. We developed segregating populations from crosses of P. sojae resistant G. soja germplasm with susceptible G. max cultivar Williams to determine inheritance of potential R genes in germplasm that responded to core effectors. We are using marker assisted breeding to map disease resistance traits in recombinant inbred (RI) lines. To better understand pathosystems, we examined host resistance and susceptibility using bioinformatics. We analyzed the interaction between Arabidopsis thaliana ecotype Col-0 and Hyaloperonospora arabidopsidis isolate Emwa1 using a publicly available RNA time-course experiment. We describe a new algorithm to sort genes into time-point specific clusters using activation and repression parameters. Gene ontology annotations were used to identify defense genes with unique expression profiles, and A. thaliana null mutants for these genes were significantly more susceptible to Emwa1 than wild-type. We plan to use these tools to rapidly identify and guide introgression of durable disease resistance into crop species.
Ph. D.

In aroma analysis, strawberries have always been the favored fruit because of their relatively high content of typical and pleasant aroma constituents. Esters, aldehydes, alcohols and sulfur compounds have been found to be the main aroma components in strawberry. In recent years, two volatile compounds, 2,5-dimethyl-4-methoxy-3(2H)-furanone (DMF) and 2,5-dimethyl-4-hydroxy-3(2H)-furanone (DHF) were reported to contribute heavily to strawberry aroma. These two compounds have been found in all wild strawberries studied, but found only in few cultivated varieties. In this work, three kinds of cultivated strawberries were sampled and analyzed. The three strawberries all belong to the Camarosa variety. They came from different growing areas: Salinas (California), Orrville (Ohio), and Memphis (Tennessee). The volatile compounds of these three strawberries were separated by Gas Chromatography (GC), and identified by Mass Spectrometer Detector (MSD). Column and experimental conditions were optimized for this particular separation. Salinas, Orrville and Memphis strawberries have very similar aroma constituents, however, in slightly differing amounts. Several unique peaks were found in each strawberry, which may well account for the differences in the aroma qualities of the three. 2-Furaldehyde was found in both Memphis and Orrville strawberries, but not in Salinas. It is a key odor compound correlated with woody aroma and it has a low odor threshold value. These two properties make it contribute negatively to the pleasant aroma of Memphis and Orrville strawberries. A compound, 2-furanmethanol, was found only in Salinas strawberries. This compound has a faint burning aroma, however, its high odor threshold value offsets its potentially bad aroma. DMF was found in all three strawberries, but no DHF was detected in any of the three. We propose a possible explanation for the absence of DHF. Ethyl (methylthio) acetate, which is a sulfur-containing compound, was found in both Orrville and Salinas strawberries. This work is the first to report its presence in strawberries of any variety. An external standard method was employed to quantify seven main aroma components found in the strawberry extracts. Aroma values were introduced and then calculated together with sensory descriptions of these compounds. Salinas strawberry was found to have the best aroma quality of the three. These results indicate that the odors of strawberries of the same variety can be different when grown in different geographical areas.
Master of Science

The most critical hurdle on the path to sustainable development in Africa and the rest of the so-called Third World is poverty, commonly manifested as food security. A number of factors threaten food security in Zimbabwe, and these include climate change, an unstable socio-political environment and economic depression. The major debates and initiatives on sustainable development often fail to focus on the eradication of poverty in southern Africa. As a result, the trade liberalisation programmes signed by African countries in economic partnership agreements leave smallholder farmers vulnerable to the influx of hybrid seed and genetically modified organisms (GMOs), which threaten local agro-biodiversity. This case study has shown that farmers select seed to plant for food as a result of various learning interactions they engage in, which include inter-generational knowledge transfer, farmer to farmer extension and external training by extension organisations and NGOs. A communities of practice (COPs) (Wenger, 2007) framework was used to gain an understanding of the learning interactions among farmers and their stakeholders in Nyanga and Marange COPs of small grain farmers in Manicaland Province, Zimbabwe, who have been working with Environment Africa (A regional NGO). A critical realist causal analysis was conducted to unravel the various causal factors influencing choice. A number of underlying structures and causal mechanisms were found to influence learning interactions and choices in these communities of practice, and they include ambivalence, which influences the changing domain and practice. Climate change, drought and risk were found to affect farmer practice, while power relations affect the community, its practice, domain, sponsorship and the learning interactions in the COPs. The political economy was also found to have a profound effect on the domain and practice. A space was found for the influence of capacity and knowledge sharing in participatory frameworks of the communities, implying that extension quality can be enhanced to promote locally adapted and diverse seed varieties for food security improvement. The study shows that a deeper understanding of the mechanisms influencing the context of teaching and learning provides a more refined insight into the learning interactions and choices of farmers. This, coupled with the social processes descriptors provided by Wildemeersch (2007) has given me a more detailed understanding of the nature of learning interactions influencing farmer choices.

Large amounts of grass residues derived from uncultivated areas are present in European regions. This biomass, which generally does not compete with food production and is partially recovered for animal feeding, represent an interesting feedstock for the supply of anaerobic digestion plants to produce renewable energy. This thesis focused on the valorisation of grass from uncultivated areas in the anaerobic digestion supply chain, with particular attention on the Veneto region. To achieve this objective, several research works have been performed in order to: -Assess the potential areas and the biomass availability considering the situation of the Veneto region; -Define the best technologies for grass mowing, harvesting, logistic and utilization in the economic, energy and environmental aspects; -Determinate the energy and environmental balance that can derive from grass valorisation in the biogas supply chain. In a first study, we demonstrated through a GIS based approach that large availability of residual grass is present in the Veneto Region, which it could be potentially utilized for anaerobic digestion. Grass from landscape management, such riverbanks, natural areas or parks, is of more interest for the energy generation in agricultural anaerobic digestion plants. The harvesting of grass in these areas can be performed with different solutions. The total costs generally are high, however systems with better operative performances can reduce the economic and energy costs due to the specialized mechanization required. Conceiving grass logistic, direct transport chain seems to be the most convenient solution under economical and energy aspects for the management of such material in short distances due to less mechanisations inputs requirement. Conversely, in longer distances, the best solution appears to be the interrupted transport chain due to the higher transport capacities. The biochemical methane potential of grass is interesting, showing that a good amount of energy can be recovered. Closing the whole energy and greenhouse gases balances is shown that the recovery of grass for energy purposes is sustainable. As consequence, grass recovering represent and opportunity to reduce the dependency of anaerobic digestion sector on energy crops and obtain a positive return, in terms of energy and emissions saved, from the landscape management operations, creating interesting job opportunities.
L’erba proveniente da aree non coltivate rappresenta un’interessante biomassa per l’alimentazione di impianti a digestione anaerobica. Tale biomassa generalmente non compete con la produzione alimentare e raramente viene recuperata per fini alimentari. L’obbiettivo di questa tesi riguarda la valorizzazione di erba da aree non coltivate per l’alimentazione di impianti a biogas, con particolare attenzione alla regione Veneto. Il raggiungimento di tale obiettivo è stato possibile attraverso diversi lavori di ricerca, con l’obbiettivo di: -Valutare il potenziale quantitativo di biomassa nella regione Veneto; -Definire le migliori tecnologie per il taglio, la raccolta, la logistica e l'utilizzazione dell’erba considerandone gli aspetti economici, energetici e ambientali; -Determinare il bilancio energetico e ambientale derivante dalla valorizzazione nella filiera di produzione del biogas. In un primo studio abbiamo dimostrato attraverso un approccio basato su GIS che in Veneto è presente una grande disponibilità di residui d’erba potenzialmente utilizzabili nella digestione anaerobica. In questo senso, l'erba derivante della gestione del paesaggio, come le banchine fluviali, le aree naturali, o i parchi, risulta essere di maggiore interesse per la produzione di energia negli impianti agricoli a digestione anaerobica. La raccolta di erba in queste aree può essere eseguita con diverse soluzioni. I costi complessivi sono generalmente elevati, tuttavia i sistemi con migliori capacità operative possono ridurre i costi economici e energetici. Considerando la logistica dell’erba, l’approccio a trasporto diretto risulta essere la soluzione più conveniente sotto gli aspetti economici e energetici per brevi distanze a causa di minori input di meccanizzazione. Viceversa, in lunghe distanze, la soluzione migliore risulta essere l’approccio di trasporto interrotto a causa delle maggiori capacità di trasporto. Dagli studi si è potuto constatare inoltre che il potenziale metanigeno dell'erba è interessante, evidenziando una buona quantità di energia potenzialmente recuperabile. I bilanci energetici e dei gas serra dimostrano che il recupero dell'erba per scopi energetici è sostenibile. Di conseguenza, il recupero dell'erba a fini energetici potrebbe costituire un'opportunità per il settore della produzione di biogas di ridurre la dipendenza da colture energetiche e ottenere un ritorno positivo, in termini di energia e di emissioni, dalla gestione del paesaggio, con la possibilità di creare interessanti opportunità di lavoro.

Mamey sapote [Pouteria spp., Sapotaceae] is a tree fruit of economic and cultural importance in Central America, Mexico, and the Caribbean islands. It contributes greatly to local economies, habitats, and human nutrition. This study is among the first to analyze genetic variability among cultivated selections of mamey sapote. The Amplified Fragment Length Polymorphism (AFLP) molecular technique was used to estimate levels of genetic diversity and similarity between individual specimens in the germplasm collections of Fairchild Tropical Botanic Garden and University of Florida. The study found overall low levels of genetic diversity within these collections. However, higher relative levels of genetic diversity were found in a group of selections from northern Costa Rica and Nicaragua. It is anticipated that future plant collection in that region will capture greater genetic diversity among cultivated types. In addition, 'Pantin' selections were used to investigate the level of variation within supposedly identical selections. This baseline information can be applied to the management and expansion of the germplasm collections by identifying duplicate selections and homonyms and by locating geographical areas for future collection.

Traditional forms of political engagement, such as voting, have been on the decline in many western nations over the last number of decades, and researchers point to younger generations as driving these changes. This dissertation seeks to deepen our understanding of the relationship young Canadians have to political participation and engage with some of the questions raised by these trends. I do so through capturing the cultural models young people use to relate to political participation, and by identifying the common trajectories and experiences of people who do and do not engage with politics. I give particular attention to the role of higher education in these trajectories, as education has long been identified as strongly related to political participation. Yet the steady rise of education attainment along with stagnating or declining participation rates, has prompted closer examination of this relationship. Cultural models that young people use to think about politics and participation, and particularly the potential role of individualist orientations that some researchers have identified as driving changing relationships to participation, are also explored in this research. This study draws from 63 semi-structured interviews with young Canadians who went to high school in low, mid, and high SES areas of Vancouver. I suggest that political engagement is primarily fostered through social contexts where such engagement is produced as natural and desirable. The family appears to play the most important role in creating such contexts, but social networks, as well as schools and workplaces, also play a role in people’s trajectories of participation. I argue that people in higher SES backgrounds are more likely to experience overlapping contexts that promote political participation, and that the impacts of higher education are mediated by previous political experiences. Finally, by outlining the common cultural models of participation, I point to the role of individualist models in producing contingent and specialized relationships to participation. I argue that one prominent model participants use to think about participation, a ‘model of interest,’ tends to help further produce politics as a specialization for those with the existing dispositions and experiences with politics.
Arts, Faculty of
Graduate

Thesis (MSc(Agric))--University of Stellenbosch, 2004.
ENGLISH ABSTRACT: The pnmary alm of this study was to investigate the national competitive advantage of the South African abalone industry. A further aim was therefore to investigate the environment, in which the South-African abalone industry operates. Secondary aims included presenting a detailed description of the roleplayers in the South African abalone industry, and considering whether the South African abalone industry can be made more competitive and, if so, how this can be achieved. The achievement of these aims required a framework to establish which data is necessary for the task. The framework selected involved a combination of Porter's Five Forces analysis and Diamond Model. The study suggests that South African abalone firms should promote South African abalone more actively, invest more funds in human resources, and that the industry's faith in government needs to be restored, which can be achieved by improving the services offered by public institutions like the South African Bureau of Standards (SABS), the Department of Trade and Industry (DTI) and Marine and Coastal Management (M&CM).
AFRIKAANSE OPSOMMING: Die doel met die studie was om die nasionale kompeterende voordeel van die Suid Afrikaanse perlemoen industrie te ondersoek. Om dit te bereik, moes die omgewing waarin die industrie fuksioneer ontleed en die rolspelers in die industrie deeglik beskryf word. 'n Verdere doel was om te bepaal of dit moontlik is om die kompeterendheid van die industrie te verhoog, en indien wel, hoe dit bereik kan word. Die raamwerk wat gekies is om die doelstellings te bereik bestaan uit 'n kombinasie van Porter se "Five Farces" analise en "Diamond Model". Die resultate dui aan dat die industrie Suid-Afrikaanse perlemoen meer aktief moet bekendstel, individuele ondernemings meer in hul menslike hulpbronne moet investeer, en dat die industrie se vertroue in die nasionale regering herstel moet word, deur die dienste te verbeter wat deur publieke instellings soos die Suid-Afrikaanse Buro van Stanaarde (SABS), Departement Handel en Nywerheid en Mariene- en Kusbestuur verskaf word.

Limbal epithelial stem cells (LESCs) produce progeny (human limbal epithelial cells, hLEC) responsible for corneal repair and maintenance. The loss, or dysfunction, of LESCs results in LESC deficiency (LESCD) characterised by corneal opacification, neovascularisation and vision loss. Current treatments include LESC transplantation through cultivated limbal epithelial transplantation (CLET). There remains a number of manufacturing and regulatory challenges with CLET, therefore, this research was performed to address these challenges and improve existing protocols. This thesis aims were; to improve the starting number of LESCs by investigating to what extent corneal storage media preserve LESCs. Secondly, to decrease risk of zoonotic agent transmission through animal-derived materials, the potential of human-derived feeders (MRC5 fibroblasts) and serum for hLEC expansion was assessed. The final aim was to examine the feasibility of collagen-based tissue equivalents (TE) containing surrogate niche cells (human dermal fibroblasts, hDFs) as alternative delivery method to current protocols utilising human amniotic membrane, a substrate predisposed to inter-and intra-donor variability. Experiments showed different corneal storage formulations can preserve poorly differentiated cells; however, investigations into other factors (donor age/ hLEC isolation) may further improve the starting number of LESCs. Human derived serum was effective in maintaining hLECs and is an adequate replacement for animal-derived serum in CLET protocols. However, human-derived MRC5 feeders should not replace animal-derived feeders in CLET manufacture due to unfavourable hLEC characteristics observed. Furthermore, future investigations into cytokines expressed by human MRC5 feeders may elucidate factors influencing hLEC behaviour. Finally, changes in hLEC characteristics and increased inflammation-associated mediator expression demonstrated hDFs were not a suitable TE surrogate niche cell; however, the potential role of such mediators in epithelial-stromal interactions should be explored. To conclude; these experiments have improved existing CLET protocols, highlighted lower-risk materials may not always be effective, and that the surrounding culture environment is integral for CLET graft success.

Thesis (DTech (Environmental-health))--Cape Peninsula University of Technology, 2018.
The management of agricultural soil and its sustainable use, namely productivity, is paramount to the agricultural industry worldwide. Large-scale agricultural product producers and scientists emphasise using environmentally benign methods to increase agricultural production such as taking a green chemistry approach to agricultural activities and/or using cultivation techniques for the bio-augmentation of agricultural soil. Some of these agricultural products, such as cassava (Manihot esculenta), produce cyanogens which promote the infestation of a cyanogen-resistant microbial species known to produce mycotoxins during decomposition. Although cyanogens and mycotoxins are important components in the functioning of the earth system and agricultural soil, their cumulative effects can result in reduced soil productivity, hence degradation. Furthermore, the presence of mycotoxins in the environment and agricultural produce is hazardous to the environment, including the biotic communities in soil and humans. Therefore, an environmentally benign (green chemistry approach) method for the reduction of cyanogens and mycotoxins was proposed for this research study. The method investigated had to be applicable in-situ for the biodegradation of cyanogens and mycotoxins. Their reduction from decomposing cassava in cultivated soil, which can be used on a small and large scale, would mitigate deleterious effects of a less reported, unknown mycotoxins producer (fungal species), Cunninghamella bertholletiae (KT275316), found to be a free cyanide- (CN-) resistant isolate. The C. bertholletiae was isolated from decomposing cassava tubers and silt, subsequent to culturing on potato dextrose agar (PDA) and in an equivalent volume of nutrient broth (NB) containing KCN (4mg/40mL) at 30 °C for 120 hrs. The isolate demonstrated an ability to biodegrade CN- into NH3 and NO3. NH3 and NO3 are nitrogenous by-products produced when young cassava plants are cultivated in a controlled environment, with 80% of the initial CN- concentration being efficiently degraded to NH3/NO3 at a conversion rate of 77.5% and 72.5% (fungus from silt and cassava), respectively, within 120 hrs. From this research, it was observed that Sub-Saharan Africa is the largest contributor to the CN- load into the environment; from cassava cultivation as per FAO data. The quantity of CN- released was estimated at 0.025x10-3 to 6.71 ppq, with further increases of 60.5% being projected to be released into the environment by 2024. As such, it was hypothetically assumed that numerous species in cassava-cultivated soil become CN- resistant as they are exposed to CN- from decomposing cassava, becoming pathogenic thus antigonistic towards other biota in cassava-cultivated soil. Consequently, the pathogenicity of the isolate was investigated against organisms (n = 12) from cassava-cultivated soil. The isolate demonstrated inhibitory pathogenic activity against some soil bacterial communities such as Oligella ureolytica, Acinetobacter sp., Pseudomonas luteola and Sphingomonas paucimobilis. The isolate also demonstrated minor antagonistic effects against Myroides sp., Stenotrophomonas maltophilia, Candida lipolytica, Cryptococcus albidus and Rhodotorula sp.. Further research to identify extracellular metabolites produced by this organism, using a fermentation method was also carried out using a liquid state fermentation technique. 30 mL Erlenmeyer flasks containing 25 mL of NB/KCN (source of CN-) at 37 °C for 168 hrs, with a volume of (5 mL), extracts from the fermentation being filtered, centrifuged, mixed with chloroform for a liquid-liquid extraction procedure subsequent to a nitrogen-facilitated blow-down technique and reconstitution with 100% analytical grade methanol, for LC/MS-TOF 6230 analysis. The analysis revealed that the isolate was able to produce the mycotoxins/secondary metabolites, Fumonisin B1 (FB1) and Deoxynivalenol (DON). Though the isolate (KT275316) demonstrated the ability to biodegrade cyanide as well as produce mycotoxin, an environmentally benign strategy (green chemistry method) with a potential to biodegrade CN-/NH3/NO3/NO2 for the biodegradation of mycotoxins was evaluated, including the identification of biodegradation by-products post-biodegradation treatment. Thus, plant extracts from Nepenthes mirabilis were found to contain enzymes such as carboxylesterase, β-glucosidase, β-glucoronidase and phosphatidyl inositol phospholipase C (identified using both quantitative and qualitative methods). The plant extracts were used with treated samples from the fermentation and were subjected to biodegradation. Thus, resulting in biodegradation by-products such as Heptadecanone Octadecanamide, Octadecenal for FB1 and Tolmetin for DON, respectively. For future research, it is therefore recommended that plant extracts with similar properties to those observed for N. mirabilis extracts (juice) be sought for application of the proposed method.

Using 'Redchief' (Junebearer) and 'Tribute' (dayneutral) cultivars, greenhouse and field studies were conducted to determine the effects of defoliation on photosynthesis, growth and yield of the strawberry. From preliminary photosynthesis experiments it was found that both 'Redchief' and 'Tribute' strawberry leaves reached maximum net photosynthesis (Pn) concurrently with full leaf expansion at approximately 8 to l0 days and 4 to 5 days, respectively, after unfolding. By exposing the plants to increasing irradiance it was determined that these cultivars were light saturated at 600 to 700)Ï molâ ¢m^-2s^-1. Neither cultivar showed a consistent diurnal pattern when Pn was monitored hourly over two consecutive days.

Master of Science

Greenhouse and field studies were conducted to determine the effects of shade on photosynthetic, growth and yield responses of "Redchief" strawberries. Plants were exposed to 0 , 30 , 47 and 63 percent shade in the greenhouse. Net photosynthesis (Pn) as measured under the shade treatments demonstrated a curvilinear decrease. Pn as measured under saturating light levels of 790 μ-tmol· m-2 · s·1 began to decrease in plants grown under 30 percent or higher shade levels. Light saturation curves for leaves expanded in full sun and then transferred to shade treatments for seven days showed a decrease in Pn saturation rate and light saturation point at 63 percent shade. Saturation curves for leaves expanded under the shade treatments exhibited a decreasing trend in saturation rate and point at all shade levels. Heavy shade (63%) reduced leaf thickness and depth of the palisade cell layers. Individual leaf area was not affected by shade treatments. As percent shade increased, total plant dry weight decreased linearly as did specific leaf weight. Shade treatments of 0, 30, 63 or 95 percent were applied over field-grown plants either in the fall during flower bud initiation, or in the fall and spring, during flower bud initiation and spring vegetative growth. Berry number was reduced as percent shade increased. Plants shaded only in the fall had higher berry number than plants shaded both in the fall and spring. Berry weight was also reduced as percent shade increased. Sugar concentration, pH and titratable acidity were not affected by shade levels or time of shade application.
Master of Science

In 1988, Arizona's early- season lettuce crop was plagued by disease and insect problems, both intensified by unseasonably high temperatures. In the western Arizona production area, an epidemic of lettuce infectious yellows (LIY) resulted in serious economic losses to growers. The yellows disease is incited by the LIY virus (LIYV), a plant virus transmitted by the sweet potato whitefly [Bemisia tabaci (Gene.)]. Disease symptoms in lettuce include stunted growth, rolling yellowing and /or reddening of infected leaves; necrotic lesions appear at or near the leaf margins at latter stages of the disease. LIYV has a wide host range which increases the difficulty of isolating lettuce fields from LIYV infected or whitefly-infested fields; also, whiteflies are resistant to insecticides. Therefore, host-plant resistance appears to be the most promising means of reducing losses due to this disease. To initiate a breeding program, commercial lettuce cultivars and breeding lines (Lactuca sativa L.), and related, cross-breeding wild lettuce species (L. serriola L. and L. saligna L.) were screened for resistance to LIYV in the western Arizona production area using natural inoculation by residence whiteflies.

Tomato (Solanum lycopsersicum) which forms a small monophyletic clade within the large Solanaceae family has been chosen as a model system for studying the Solanaceae genome, fruit development and ripening. At that time, many efforts have been devoted to the analysis of the genetic diversity of tomato species, little work has focused on the analysis epigenetic diversity in this clade, although there is a general agreement that epigenetic processes play essential role in the phenotypic diversity in animal and plant system. As first step, DNA methylation level was analyzed in leaves and fruits of various wild and cultivated tomato species.Additionally, the Enhancer of zest (E(z)) gene family has been analyzed. In tomato, the E(z) family consists in two functional genes (SlEZ1, SlEZ2) and in a pseudogene (SlEZ3). In addition, the epigenetic stability is an important consideration that could have a significant on strategies for crop breading. Finally, we made a fine characterization of the different aspects of fruit development and ripening.

La maduixa cultivada, Fragaria x ananassa, és un cultiu mundialment important. Les seves fruites s’ aprecien pel balanç entre la dolçor i la acidesa, i pel seu aroma característic. Malgrat que tradicionalment els programes de millora de maduixa estaven enfocats en el rendiment i la resistència a les malalties, actualment, l’interès per la qualitat de la fruita s’ha vist augmentat. La maduixa cultivada és una espècie allo-octoploid (2n = 8x = 56) i el seu genoma és altament diploiditzat. La naturalesa poliploide augmenta la dificultat per analitzar l’herència genètica dels caràcters quantitatius. El coneixement que es té sobre l’espècie model F. vesca es pot transferir fàcilment a la maduixa cultivada, ja que el seu genoma és un dels subgenomes de les espècies octoploides. Amb l’ objectiu de determinar l’herència de l’ aroma de la maduixa i d’altres caràcters de la qualitat de la fruita, hem estudiat amb profunditat dues poblacions de millora, una F1 i una F2. La població F1 (‘FC50xFD54’ ) s’ha obtingut amb l’ encreuament de les línies de millora ‘FC50’, seleccionada per l’ aroma a maduixa del bosc, i ‘FD54’ , seleccionada per l’ aroma afruitat. Hem construït un mapa genètic saturat per a la població ‘FC50xFD54’ amb 1495 marcadors polimòrfics, del xip IStraw35k, agrupats en 28 LGs i repartits en 3451cM. La comparació del mapa mostra una alta col·linealitat entre les posicions dels marcadors del mapa genètic del ‘FC50xFD54’ amb el mapa consens de F. x ananassa i amb els genomes diploide i octoploide de Fragaria. A més, hem millorat el mapa genètic de la població F2 (‘21AF’ ), obtinguda de l’ encreuament entre les línies d’ elit ‘Camarosa’ , seleccionada per la qualitat de la fruita i ‘Dover’ , seleccionada per ser robusta. El mapa resultant està compost per 7977 marcadors polimòrfics, agrupats en 28 LGs i cobreix una longitud de 2056cM. La variació fenotípica de l’ acumulació dels compostos volàtils (VOCs), gust (acidesa i SSC) i caràcters d’ aparença com la forma, el color o la fermesa s’ ha estudiat detalladament en les fruites madures d’ aquestes dues poblacions en diferents collites. L’ anàlisi de la segregació i de la correlació entre aquests caràcters han permès la detecció de possibles caràcters co-regulats i l’ anàlisi de QTL han permès localitzar centenars de regions que expliquen la variació observada. Els compostos orgànics majoritaris que contribueixen en la preferència dels consumidors són els sucres, els àcids i els VOCs. S’ han identificat un total de 58 VOCs en ‘FC50xFD54’ i s’han localitzat 19 QTLs estables. D’entre aquests, 22 QTLs amb alta estabilitat estan relacionats amb els compostos volàtils claus (KVCs) que són objectiu d’ alguns programes de millora de l’ aroma. A més, alguns d’ aquests QTLs pels KVCs han estat validats en la població ‘21AF’ . Ressaltem la detecció d’ un QTL pels terpens localitzat al LG3B, diferents QTLs per èsters als LG1A, LG4B, LG6A i LG7D, un QTL pel metil antranilat al LG7A i un altre per la γ-decalactona al LG3D. Les anàlisis del sabor i de l’aparença han permès localitzar un total de 77 QTLs estables a la població ‘FC50xFD54’ i de 31 QTLs a la població ‘21AF’ . Ressaltem un QTL pel color intern trobat al LG1A i dos QTLs per la forma de la fruita localitzats al LG4C i LG6D. La població ‘FC50xFD54’ segrega per un allargament del coll no desitjat, mapant dos QTLs als LG3A i LG4B. Aquesta tesi ha contribuït en la millora del coneixement genètic sobre la qualitat de la fruita, específicament l’aroma, el gust i l’ aparença. A més, els SNPs seleccionats lligats a un caràcter d’ interès podrien utilitzar-se en MAS per satisfer la demanda dels consumidors.
La fresa cultivada, Fragaria x ananassa, es un cultivo importante mundialmente. Sus frutas son apreciadas por su sabor, balance entre dulzura y acidez y por su característico aroma. Tradicionalmente, los programas de mejora de fresa han estado enfocados en la mejora del rendimiento y de la resistencia a enfermedades, pero actualmente, el interés en la calidad de la fruta se ha incrementado. La fresa cultivada es una especie allo-octoploide (2n = 8x = 56) y su genoma está altamente diploidizado. Su naturaleza poliploide dificulta el análisis de la herencia genética de los caracteres cuantitativos. El conocimiento en la especie modelo F. vesca se puede transferir fácilmente a la fresa cultivada, ya que su genoma es también uno de los subgenomas en las fresas octoploide. Con el objetivo de conocer la herencia del aroma y de otros caracteres de la calidad de la fruta, hemos estudiado en profundidad dos poblaciones de mejora, una F1 y una F2. La población F1 (‘FC50xFD54’) fue obtenida del cruzamiento entre las líneas de mejora ‘FC50’, seleccionada por su aroma a fresa del bosque, y ‘FD54’, seleccionada por su aroma afrutado. Hemos construido un mapa genético saturado para esta población con 1495 marcadores polimórficos del chip IStraw35k agrupados en 28 LGs y repartidos en 3451cM. La comparación de los mapas muestra una alta colinealidad entre las posiciones de los marcadores del mapa genético ‘FC50xFD54’ y del mapa consenso de F. x ananassa y también con los genomas diploide y octoploide de Fragaria. Además, hemos mejorado el mapa genético de la población F2 (‘21AF’), obtenida del cruzamiento entre las líneas ‘Camarosa’, seleccionada por la calidad de su fruta, y ‘Dover’, por ser robusta. El mapa resultante está compuesto por 7977 marcadores polimórficos, agrupados en 28 LGs y cubriendo 2056cM. La variación fenotípica de la acumulación de los compuestos volátiles (VOCs), gusto (acidez y SSC) y caracteres de apariencia como la forma, el color o la firmeza en las frutas maduras de las dos poblaciones ha sido estudiada detalladamente en diferentes cosechas. Los análisis de la segregación y correlación entre estos caracteres han permitido la detección de posibles caracteres co-regulados y los análisis de QTL han localizado cientos de regiones explicando la variación observada. Los compuestos orgánicos que contribuyen en la preferencia de los consumidores son los azucares, los ácidos y los VOCs. Un total de 58 VOCs fueron identificados en la población ‘FC50xFD54’ localizando 179 QTLs estables. De entre estos QTLs, 22 con alta estabilidad fueron relacionados con los compuestos volátiles clave (KVCs), objetivo de algunos programas de mejora. Además, algunos de estos QTLs para los KVCs fueron validados en la población ‘21AF’. Resaltamos la detección de un QTL para los compuestos terpenoides localizado en LG3B, diferentes QTLs para compuestos de tipo éster en LG1A, LG4B, LG6A y LG7D, un QTL para metil antranilato en LG7A y otro para γ-decalactona en LG3D. Los análisis del sabor y la apariencia han reportado un total de 77 QTLs estables en la población ‘FC50xFD54’ y 31 QTLs en la población ‘21AF’. Resaltamos un QTL para el color interno encontrado en LG1A y dos QTLs para la forma de la fruta localizados en LG4C y LG6D. La población ‘FC50xFD54’ segregaba por un carácter no deseado, el alargamiento del cuello, y el análisis de QTLs ha mapeado QTLs en LG3A y LG4B. Esta tesis ha contribuido a mejorar el conocimiento genético sobre la calidad de la fruta, específicamente el aroma, el gusto y la apariencia. Además, los SNPs seleccionados ligados a un carácter de interés podrían ser usados en la selección asistida por marcadores (MAS) para satisfacer la demanda de los consumidores.
Cultivated strawberry, Fragaria x ananassa, is an important crop cultivated worldwide. Its fruits are appreciated for their balance between sweetness and acidity and for their characteristic aroma. Although, traditionally, strawberry breeding programs were essentially focused on yield improvement and disease resistance, currently, there is also an interest in improving some fruit quality traits. Cultivated strawberry is allo-octoploide (2n = 8x = 56) and its genome is highly diploidised. Its polyploid nature increases the difficulty to analyse the genetic heritability of quantitative traits. The knowledge of the model species F. vesca can be easily transferred to cultivated strawberry, since its genome constitute one of its subgenomes. In order to elucidate the heritability of strawberry aroma and other fruit quality traits, we have studied in depth two breeding populations, an F1 and an F2. The F1 population (‘FC50xFD54’) was produced through a cross between the breeding lines ‘FC50’, selected for its wild strawberry aroma, and ‘FD54’, selected for its fruity aroma. We have constructed a saturated ‘FC50xFD54’ genetic map with 14595 polymorphic markers, from IStraw35k array, grouped in 28 LGs and spanning 3451cM. The maps comparison shows high collinearity between marker position in ‘FC50xFD54’ genetic map and the F. x ananassa consensus map and with the diploid and octoploid Fragaria genomes. Additionally, we improved the genetic map of the F2 population (‘21AF’), derived from a cross between two elite lines ‘Camarosa’, selected for its fruit quality, and ‘Dover’, selected for its robustness. The resulting map is composed of 7977 polymorphic markers grouped in 28 LGs and covers a total length of 2056cM. The phenotypic variability of ripe fruits in these two populations for volatile compounds accumulation (VOCs), taste (acidity and SSC) and appearance traits such as shape, colour and firmness has been thoroughly studied in different harvests. The analysis of segregation and the study of correlation between traits allowed the detection of possible co-regulated traits and the QTL analysis located hundreds of regions that explain the variance of these traits. The main organic compounds contributing to consumer preferences are sugars, acids and VOCs. A total of 58 different VOCs was identified in ‘FC50xFD54’ and 179 stable QTLs were localised. Of these QTLs, 22 presenting high stability were related to key volatile compounds (KVCs) which are target of some aroma breeding programs. Additionally, some of these KVC QTLs were validated in the ‘21AF’ population. We highlight the detection of a QTL for terpene compounds in LG3B, different QTLs for ester compounds in LG1A, LG4B, LG6A and LG7D, a QTL for methyl anthranilate in LG7A and another for γ-decalactone in LG3D. The analysis of taste and appearance traits reported a total of 77 stable QTLs in the ‘FC50xFD54’ population and 31 QTLs in the ‘21AF’ population. We highlight an internal colour QTL found in LG1A and two fruit shape QTLs in LG4C and LG6D. ‘FC50xFD54’ population segregated for an undesirable neck phenotype whose QTLs were mapped in LG3A and LG4B. The aim of this thesis was to increase the genetic knowledge of fruit quality, specifically aroma, taste and appearance traits. Furthermore, the selected SNPs linked to a desired trait could be applied in marker assisted selection (MAS) to satisfy the consumer demand.
Universitat Autònoma de Barcelona. Programa de Doctorat en Biologia i Biotecnologia Vegetal

An increased global food demand requires an increase in agricultural land use, which in turn affects the hydrologic cycle. A central process in this regard is infiltration of rainfall through the land surface. While there are standard values available for different soil types, land cover also has a documented influence on infiltration rates. This makes infiltration highly variable acrosss patiotemporal scales and as such, difficult to measure in field, thus selection of an appropriate measurement technique is important to consider. Therefore, this study aimed to establish a method for robust infiltration measurements and compare rates from various crops (rice andmaize) and soils (sand and clay) to see if there is consistency between physical controls on infiltration and farming practices. The study area is located near the town of Ifakara in south-central Tanzania. Data were gathered during eight weeks (October- November) using variousring infiltrometer set-ups. The results from 12 comparative infiltration measurements indicated that a smaller ring implies less measurement precision. Precision was improved by using a doublering setup and/or a larger single ring. Infiltration measurements from the nine agricultural fields corresponded well to estimations from the Horton infiltration equation (correlation coefficient >0.98). The results from all 36 measurements indicated a statistically significant difference between crop types as well as between soil types. The significance was, however, higher for soils compared to crops. Part of the inconsistency of infiltration rates could be explained by the cultural factor where traditions are important for crop choice and farming. Further, the measured infiltration confirmed the large spatial variations of infiltration rates both within and across fields, with implications for large scale agricultural development.