The focus of this study is to gain a better understanding of the hazards affecting the transportation of avocados from farm to packhouse by developing an effective risk assessment tool farmers can use. The transport related factors considered in this study encompass all hazards which may affect the avocado, from the point the fruit is picked to the point the avocado is packed at the packhouse. The study has been undertaken in five stages, namely:  A literature study split into four main stages, including an investigation into avocado specific hazards, transportation related hazards, market influencers and investigating analysis tools.  Data collection (including environmental indicators, accelerations and GPS measurements) stemming from field tests conducted with a smart avocado device (smAvo);  Data analysis of the smAvos, including assessing the kinetic energy the avocado experiences;  Risk analysis and Bayesian Network Development including those hazards identified in the literature study as well as from the smAvo, and  Bayesian Network analysis, using Delphi Fuzzy methodology and smAvo data to determine the influence of the combination of risk factors identified. The risk assessment tool was developed through the use of Bayesian Networks. This tool eliminates the guesswork of what causes the largest reduction in shelf life/waste and therefore profit. The Network considers the joint probability of these hazards, and posterior probabilities of any subset of variables when evidence is introduced. The Bayesian Network is analysed and optimised by means of finding factors that will cause the greatest improvement of shelf life and decreased damage. A converse analysis is done by determining the effect of, for example poor road conditions or truck type. The result of this analysis provides the farmer with a decision-making tool which will optimise processes, increase profits (by reducing waste) and eliminate any guesswork. The Network can be used by the farmer and updated as new evidence is discovered. The analysis concludes with the most damaging areas within the network is at harvest, followed by truck transportation effects, packhouse conditions and lastly farm transportation effects. In order to optimise the network, emphasis is put on the plant condition, followed by any delay in transportation and the picking technique used during harvest. A “what-if” analysis was done which concluded poor road conditions can increase overall damage by 0.44 per cent, whereas poor harvest conditions can increase this to 12.57 per cent. / Dissertation (MEng (Transportation Engineering))--University of Pretoria, 2020. / Civil Engineering / MEng (Transportation Engineering) / Unrestricted

El presente trabajo de investigación tiene como propósito determinar cómo los elementos de la oferta exportable influyeron en el incremento de la internacionalización de las empresas exportadoras de palta Hass hacia China durante los años 2014 al 2018. La palta Hass ha tenido un crecimiento de las exportaciones de US$800 millones en el 2018 (Chávez, 2019). Es preciso señalar, el Perú tiene los mercados de destino de palta Hass a Holanda, Estados Unidos, España, Chile y China. No obstante, se elige China por tener un crecimiento en exportaciones durante el periodo de estudio (SUNAT, 2019). Para el análisis y desarrollo de la investigación, se presentan cinco capítulos: marco teórico, plan de investigación, metodología de trabajo, desarrollo – aplicación y análisis de los resultados. La investigación es cuantitativa, en donde se utiliza un cuestionario como instrumento, dirigido a profesionales relacionados al tema. Es preciso señalar, las empresas que fueron seleccionadas para la investigación son aquellas que representan al 80% de las exportaciones de palta Hass hacia China durante el periodo 2014 al 2018 (SUNAT, 2019). De este modo, se identifica que los elementos de la oferta exportable: disponibilidad de producto, capacidad económica – financiera y capacidad de gestión han influido en el incremento de la intercionalización de las empresas exportadoras de palta Hass hacia China durante el periodo 2014 a 2018. No obstante, se debe continuar con la misma gestión, teniendo en cuenta la importancia de gestionar las certificaciones y requisitos necesarios. / The purpose of this research work is to determine how the elements of the exportable supply influenced the increase in the internationalization of HASS avocado export companies to China during the years 2014 to 2018. The Hass avocado has had an export growth of US $ 800 million in 2018 (Chavez, 2019). It should be noted, Peru has Hass avocado destination markets to the Netherlands, the United States, Spain, Chile and China. However, China is chosen because it has a growth in exports during the study period (SUNAT, 2019). For the analysis and development of research, five chapters are presented: theoretical framework, research plan, work methodology, development - application and analysis of the results. The research is quantitative, where a questionnaire is used as an instrument, aimed at professionals related to the subject. It should be noted, the companies that were selected for research are those that represent 80% of HASS avocado exports to China during the period 2014 to 2018 (SUNAT, 2019). In this way, it is identified that the elements of the exportable offer: product availability, economic - financial capacity and management capacity have influenced the increase in the internationalization of HASS avocado export companies to China during the period 2014 to 2018. However, the same management must be continued, considering the importance of managing the necessary certifications and requirements. / Tesis

Plants synthesize and store oil, mostly triacylglycerol (TAG), in various storage tissues that serves as a source of carbon and energy. The process is transcriptionally controlled by WRINKLED1 (WRI1), a member of the APETALA2 (AP2) class of transcription factors, that regulates most of the fatty acid biosynthesis genes. Among the four Arabidopsis WRI1 paralogs, only WRI2 is nonfunctional and failed to complement wri1-1 mutant seeds. The oleaginous Avocado (Persea americana) fruit mesocarp (60-70% DW oil) showed high expression levels for orthologs of WRI2, along with WRI1 and WRI3. While the role of WRI1 as a master seed oil biosynthesis regulator is well-established, the function of WRI1 paralogs in non-seed tissues is poorly understood. We conducted structural analyses to elucidate distinct features of avocado WRI paralogs compared to their orthologs in seed tissues. Comprehensive comparative in silico analyses of WRI1 paralogs from Arabidopsis (dicot), maize (monocot), and avocado revealed distinct features associated with their function. Our analysis showed the presence of only one AP2 domain in all WRI2 orthologs, compared to two AP2 in others. The highly conserved N-terminal region and the less conserved C-terminal regions make up the primary structure of the proteins, with amino acid composition bias characteristic of intrinsically disordered proteins (IDPs). Additionally, the avocado WRI2 showed a high proportion of random coil secondary structure, although it lacks a C-terminal intrinsically disordered region (IDR). Also, both WRI1 and WRI2 have distinct predicted phosphorylation target sites compared to their orthologs, whereas WRI2 lacks a PEST motif. Finally, through transient expression assays, we demonstrated that both avocado WRI1 and WRI2 are functional and drive TAG accumulation in Nicotiana benthamiana leaves. Our study showed that avocado WRI2 is structurally different and is functional, unlike its ortholog in Arabidopsis. This study provides us with new targets to enhance oil biosynthesis in plants.

No description available.

No description available.

Avocado is an economically important crop with ~70% oil in its fruit tissue, which is an essential component of human diet. The steady increase in global demand for avocado production (9%/year) has drawn attention to the importance of understanding the genetic regulation of triacylglycerol (TAG) accumulation. Using RNA-seq approach, mesocarp-specific regulation and biosynthesis of TAG in developing avocado fruit was analyzed. During the period of TAG accumulation in the mesocarp, an increased expression was noted for genes mostly associated with hexose metabolism in plastids, including pyruvate kinase, relative to cytosol, which is likely associated with the need for higher pyruvate flux directed toward plastid fatty acid synthesis. A corresponding increase in expression for plastidial fatty acid synthesis genes was also noted but not for TAG assembly genes. Additionally, WRINKLED1 (WRI1), a regulatory element typically associated with seed oil biosynthesis, was also highly expressed in oil-rich mesocarp of avocado, along with two other isoforms of WRI. Transcriptomics also revealed that multiple acyltransferases that participate in rate-limiting step in TAG synthesis might be active concomitantly in mesocarp to achieve higher levels of TAG accumulation. Similar observations were previously made with transcriptome analysis of oil-rich seed and non-seed tissues. Together these data suggest a ubiquitous role for WRI1 and that a major point of regulation of oil biosynthesis in oilrich mesocarp tissue most likely occurs at the level of source and not sink. Overall, this study provides a foundation for functional genomics required to direct metabolic engineering efforts to enhance avocado oil yield.

The neutral lipid triacylglycerol (TAG) is the main storage lipid in plants. When stored in seeds, TAG provides the carbon and energy source during germination. There is significant human nutritional demand for vegetable oil, but its use in production of renewable biomaterials and fuels has intensified the need to increase oil production. In plants, the final and committed step in TAG biosynthesis is catalyzed by diacylglycerol acyltransferases (DGAT) and/or a phospholipid: diacylglycerol acyltransferases (PDAT). Both DGAT and PDAT contribute to seed TAG biosynthesis in an independent or overlapping manner, depending on the species. However, in nonseed tissues such as mesocarp of avocado, the regulation of TAG biosynthesis is not well-studied. Based on the transcriptome data of Persea americana it is hypothesized that both DGAT and PDAT are likely to catalyze the conversion of diacylglycerol to TAG. In this study, putative DGAT1 and DGAT2 were identified and comprehensive in silico analyses were conducted to determine the respective start codons, full-length coding sequences, transmembrane domains, predicted protein structures and phylogenetic relationships with other known DGATs. These data reveal that the putative DGATs of a basal angiosperm species retain features that are conserved not only among angiosperms but also other eukaryotes. For further biochemical characterization, the avocado DGATs were expressed in a TAGdeficient yeast strain and lipotoxicity rescue assays were conducted. The complementation of this yeast strain confirmed enzyme activity and supported the possible role of both avocado DGATs in TAG biosynthesis. Future studies will be focused on determining the substrate specificity of DGAT and its role, relative to PDATs in TAG biosynthesis in avocado mesocarp.

Unlike most other fruits that accumulate oil in seed tissues, avocado stores large amounts of oil in the form of triacylglycerol (TAG) in its mesocarp tissue. The regulation of TAG biosynthetic pathways in such nonseed tissues is poorly understood. RNA-Seq was used to identify the transcriptional networks underlying TAG biosynthesis in developing mesocarp of avocado. Deep transcriptional profiling studies revealed that several transcripts were differentially represented between the early and late developmental stages of mesocarp. The temporal expression pattern of transcripts associated with fatty acid biosynthesis in plastid coincided with increasing oil content. Furthermore, except for the transcripts that likely encode enzymes involved in the terminal step in TAG synthesis, others involved in TAG assembly in the endoplasmic reticulum were poorly expressed. This pattern of higher expression for genes involved in fatty acid synthesis but not TAG assembly was similar to previously observed pattern in other seed and nonseed tissues. Comparative analysis of transcript levels for about 1500 transcription factors, across different species and oil-storing tissues, also revealed that WRINKLED1 may be highly conserved across species but transcriptional regulation of oil biosynthesis, includes distinct tissue-specific features. In conclusion, while the biochemical pathways for oil biosynthesis in nonseed tissue are highly similar to that of seed tissues, certain distinctive modes of regulation of fatty acid biosynthesis and TAG assembly likely occur in oil-rich nonseed tissues.

Avocado is an economically important crop with ~ 60-70 % oil, by dry weight, in its fruit mesocarp tissue. The steady increase in global demand for avocado (9% per year) has driven interest to identify the biochemical and molecular factors that regulate its triacylglycerol (TAG, oil) biosynthesis. Using 454- and Illumina-based RNA-Seq approaches, we examined the transcriptional basis for TAG biosynthesis in developing mesocarp of avocado, in relation to other seed and non-seed tissues. Deep transcriptional profiling data allowed us to identify several transcripts that were differentially represented between the early and late developmental stages of mesocarp. Additionally, in all oil-rich tissues analyzed, irrespective of the species, an increased expression was noted for genes mostly associated with fatty acid biosynthesis in plastid, but much less increase in those for TAG assembly in the endoplasmic reticulum. Transcripts associated with hexose metabolism in plastid also showed higher expression, relative to cytosol; this is likely associated with the need for high pyruvate flux directed toward plastid fatty acid synthesis. Moreover, WRINKLED1 transcription factor, a regulatory element associated with oil biosynthesis in seed and non-seed tissues of monocot and dicot plants, was identified in avocado as well. Our studies point to distinctive modes of regulation of fatty acid biosynthesis and TAG assembly that are conserved in both seed and non-seed oil-rich plants. In addition to improving avocado oil production, our study will lead to understanding regulation of oil biosynthesis in coordination with fruit development and identification of ways to generate oil-rich bioenergy crops; a direct implication for the science & society. This study provides an evolutionary insight into conserved nature of oil biosynthesis in a basal angiosperm (avocado) in relation to a monocot (oil palm) and a dicot (brassica). This research will lead to publications for students, sustain existing collaborations (Israel, CA, FL avocado researchers) and generate external funds.

The avocado mesocarp contains up to 60-70% oil by dry weight where triacylglycerol (TAG) is the major constituent. This neutral lipid, TAG is utilized by plants for the carbon and energy source when stores in seed tissue. There is significant human nutritional demand for vegetable oil, but its use in production of renewable biomaterials and fuels has intensified the need to increase oil production. In plants, the final and committed step in TAG biosynthesis is catalyzed by diacylglycerol acyltransferases (DGAT) and/or a phospholipid: diacylglycerol acyltransferases (PDAT). Both DGAT and PDAT contribute to seed TAG biosynthesis in an independent or overlapping manner, depending on the species. However, the regulation of TAG biosynthesis is not wellstudied in nonseed tissues such as mesocarp of avocado. Based on the transcriptome data of Persea americana it is hypothesized that both DGAT and PDAT are likely to catalyze the conversion of diacylglycerol to TAG. In this study, putative DGAT1 was identified and comprehensive in silico analyses were conducted to determine the respective start codons, full-length coding sequences, transmembrane domains, predicted protein structures and phylogenetic relationships with other known DGAT1s. These data reveal that the putative DGATs of a basal angiosperm species retain features that are conserved not only among angiosperms but also other eukaryotes. For further functional analysis, the avocado DGAT1 was expressed in H1246, a TAG-deficient yeast strain and lipotoxicity rescue assays, TLC analysis, Nile Red staining were conducted. The complementation of this yeast strain confirmed enzyme activity and supported the possible role of avocado DGAT1 in TAG biosynthesis. Finally, substrate specificity of DGAT was determined by incubating microsomes with different radiolabeled substances and found that avocado DGAT1 has a preference toward oleic acid (18:1) compare to palmitic acid (16:0) while it is converting diacylglycerol (DAG) to triacylglycerol. All these data suggested that avocado DGAT1 is functional and making TAG with high preference of oleic acid over palmitic acid.