Avocados are an economically important crop in South Africa and are mainly exported to Europe. As with any other tropical and subtropical crop, avocados are prone to pre- and postharvest diseases. Until recently, chemical control was the only effective measure to control fungal avocado pathogens In 1987, a Bacillus subtilis isolate was found that showed promise as a biocontrol agent in both pre- and postharvest applications to control postharvest diseases. However, over time variable results has been obtained in semi commercial trials. From the original B. subtilis isolate several subcultures have been made and used over a 15 year period in various experimental trials. The dual culture technique was used to compare the biocontrol activity of the subcultures against postharvest pathogens (Colletotrichum gloeosporioides, Phomopsis perseae, Dothiorella aromatica and Lasiodiplodia theobromae). The subcultures differed significantly in their effectiveness and genetic stability. No difference between the subcultures could be found when DNA fingerprinting using RISA PCR was used. The most effective subculture, MI-14, was used in further studies. The mode of action employed by a biocontrol agent is of utmost importance and can be used to enhance its efficacy. In a previous study it was hypothesized that antibiosis as well as competition for nutrients and space is the modes of action involved in biocontrol of B. subtilis against postharvest pathogens of avocado. The direct interaction between B. subtilis and C. gloeosporioides on avocado fruit were observed using scanning electron microscopy. Cells of B. subtilis were observed to colonize the hyphae of C gloeosporioides. In some instances, hyphal walls were lysed in the presence of B. subtilis and may be due to the presence of enzymes or antibiotic substances. Conidia of C. gloeosporioides did not germinate in the presence of B. subtilis. Diffusible inhibitory metabolites active against C. gloeosporioides were produced in vitro by B. subtilis. Inhibitory volatile substances were also produced by B. subtilis and were found to be active against P. perseae, D. aromatica and L. theobromae but not C. gloeosporioides. Siderophores production as well as chitinase, amylase, lipase and proteinase activity were also observed and may play a role in antagonism. Antibiotic production by B. subtilis is a well-known phenomenon. Most antibiotics are polypeptides and lipopeptides. The involvement of phenolic metabilites in biocontrol by B subtilis is less known. A seven-day-old culture of B. subtilis in a minimal medium was analyzed for the presence of free acid phenolic compounds active against fungi. Free acid phenolic metabolites were found and separated using layer chromatography. TLC plates containing the separated spots were sprayed with Clasdosporium cladosporioides and plates were observed for inhibition zones. The phenolic substances were present at 7.06 ± 0.95 mg gallic acid ml-1. The phenolic substances fall in the hydroxycinamic acid group due to their fluorescent coloring under UV at 350 nm. The mode of action involved is also influenced by environmental factors. The effect of temperature and carbon- and nitrogen sources of the in vitro inhibitory activity of B. subtilis against C. gloeosporioides, P. perseae, D. aromatica and L. theobromae were investigated using the dual culture technique. The most effective temperature range for B. subtilis was found to be between 20 and 37°C. At temperatures lower than 15°C, B. subtilis was found to be not very effective, suggesting why postharvest applications followed directly by cold storage do not always work effectively. D-arabinose and D-(+)-mannitol evaluated as carbon source as well as L-glutamic acid, L-glutamine and L-(+)-asparagine used as nitrogen sources support in vitro antagonism against the pathogens most effectively. They also do not support the growth of C. gloeosporioides, P. perseae, D. aromatica and L. theobromae. These nutrients can potentially be the most effective ones to incorporate in commercial B. subtilis formulations. The study showed the potential role of antagonistic free acid phenolic substances, volatiles and siderophores on inhibition of fungal avocado pathogens. Further studies to confirm their in situ activity are required. In conclusion, various factors affect the efficacy of B. subtilis against postharvest pathogens of avocado. These factors should be kept in mind when applying the commercial product in order to achieve the best results. / Dissertation (MSc (Microbiology))--University of Pretoria, 2011. / Microbiology and Plant Pathology / unrestricted

This thesis examines the effects on demand, supply, imports, and prices of partial easing of sanitary and phytosanitary (SPS) barriers to trade in the U.S. market in the case of Mexican avocados. The SPS Agreement plays a role in the avocado market studied here through its implications for negotiations between countries that have not utilized the formal channels of the WTO for resolving disputes. A quarantine in place from 1914 until very recently banned entry of Mexican avocados into the U.S. market on grounds of risk of pest infestation. Since the early 1970s this quarantine has been a cause of dispute between the Mexican and U.S. governments, resulting in elaborate evaluations of possible pest risks and risk mitigation procedures that might be carried out. However, after the initiation of negotiations for the North American Free Trade Agreement (NAFTA) in 1991, the import ban was partially eased in 1995 allowing Mexico access to the Northeastern part of the U.S. during four winter months. After three years of successfully exporting without any pest outbreaks, Mexico requested increased access to an additional part of the U.S. market, which it was granted in 2001. This study develops a partial equilibrium trade model to investigate the effects that this increased access will have on the avocados markets. Hypothesized further increases in access are described, and their potential effects are evaluated as well. / Master of Science

Motivation The objective of the South African Avocado Growers Association (SAAGA) is to increase the demand of avocados by advertising, promoting and other means deemed fit by them. In order to promote and advertise a product, consumer research has to be done to determine the consumers' attitudes towards and beliefs concerning the product. These findings then need to be followed up by scientific studies, targeted at specific problems and target groups to yield scientific evidence. Little consumer research has been done on avocados and studies investigating the health effects of avocados are limited, with available literature only focussing on the cholesterol lowering effect of avocados. Objectives Firstly, the objective is to investigate the beliefs and attitudes of the South African consumer towards avocados and health; to determine whether gender, age group, race or living standard influence the consumers beliefs towards avocados. Secondly, the objective is to dispel the myth that avocados are fattening and should therefore be avoided in energy restricted diets; to examine the effects of avocados, a rich source of monounsaturated fatty acids, as part of an energy restricted diet on weight loss, serum lipids, fibrinogen and vascular function in overweight and obese subjects. Methods Consumer study: One thousand nine hundred and ninety-seven South African individuals, randomly selected from metropolitan areas in South Africa, participated in this survey. Data were weighed to reflect the adult metropolitan population based on gender, age and race distribution. The total population (10 695 000) was representative of both genders (5 423 000 men and 5 272 000 women) and major race groups (2 615 000 whites, 6 252 000 blacks, 1 255 000 coloureds and 573 000 Indians) from different age groups and living standards. The questionnaires were designed by a multidisciplinary team and consisted of seventeen foodrelated questionnaires, of which one questioned the beliefs regarding avocados. Trained field workers administrated questionnaires by conducting face-to-face interviews with consumers. The market research company, MARKINOR, was contracted to collect the data. Quantitative data was statistically analysed in order to generate the relevant descriptive statistics, cross tabulations and statistical tests. SUMMARY Dietary intervention study: Sixty one free-living volunteers (13 men; 48 women), with a mean (standard deviation) body mass index (BMI) of 32 (3.9) kg/m2, participated in this randomised, controlled parallel study. The subjects were paired according to gender, BMI and age and randomly assigned to one of two groups. The experimental group consumed 200 g of avocado (1 avocado) per day, substituting 30 g of other mixed dietary fats, and the control group excluded avocado from their energy restricted diet for six weeks. Seven-day isoenergetic menu plans were given according to mean energy requirements of both genders to provide 30% fat, 55% carbohydrates and 15% protein of total energy intake. Anthropometric measurements, physical activity, dietary intakes, blood pressure and arterial compliance were measured with standard methods at the beginning and end of the intervention. Fasting blood samples were drawn at the beginning and end of the intervention period. Results Consumer study: There were no practical significant differences in the consumers responses in terms of gender or age. Practical significant differences were found between different race and LSM (Living Standard Measure) groups for some variables. The overall response of consumers towards the effect of avocados on health, heart health, children's health and the health effects associated with the fat content of avocados were very positive. However, almost half the consumers are still not convinced of or are uncertain as to the cholesterol content of avocados, while 47% of the consumers still believe that avocados are fattening. More than 80% of the consumers agreed that avocados are a good source of vitamins and minerals, and 76% consider avocados to be a good source of fibre. Almost 70% of the consumers agreed that avocados are good for sportsmen and -women. Avocados were seen by 49% of the consumers to be an aphrodisiac. Dietary intervention study: Fifty-five subjects completed the study. Compliance with avocado intake in the experimental group was 94.6%. Anthropometric measurements (weight, body mass index and percentage body fat) decreased significantly in both groups during the study (p<0.001), and the change was similar in both groups. Serum lipid levels (total cholesterol, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol and triglycerides), fibrinogen, blood pressure and arterial compliance did not change significantly within or between the two groups. SUMMARY Conclusions Consumer study: There are still a few myths and misconceptions that exist among some consumers regarding avocados, especially with regard to sexual functioning, cholesterol content, and fattening effect of avocados. The agricultural industry can use these results to plan different marketing campaigns focused on certain target groups to change the misperceptions concerning avocados and convey the positive nutritional value of avocados. Dietary intervention study: The consumption of 200 g avocado per day, within an energy restricted diet, does not compromise weight loss when substituted for 30 g of mixed dietary fat. The serum lipid levels, plasma fibrinogen, arterial compliance, as well as systolic and diastolic blood pressure were not affected by weight loss or avocado intake. / Thesis (M.Sc. (Nutrition))--North-West University, Potchefstroom Campus, 2004.

Motivation The objective of the South African Avocado Growers Association (SAAGA) is to increase the demand of avocados by advertising, promoting and other means deemed fit by them. In order to promote and advertise a product, consumer research has to be done to determine the consumers' attitudes towards and beliefs concerning the product. These findings then need to be followed up by scientific studies, targeted at specific problems and target groups to yield scientific evidence. Little consumer research has been done on avocados and studies investigating the health effects of avocados are limited, with available literature only focussing on the cholesterol lowering effect of avocados. Objectives Firstly, the objective is to investigate the beliefs and attitudes of the South African consumer towards avocados and health; to determine whether gender, age group, race or living standard influence the consumers beliefs towards avocados. Secondly, the objective is to dispel the myth that avocados are fattening and should therefore be avoided in energy restricted diets; to examine the effects of avocados, a rich source of monounsaturated fatty acids, as part of an energy restricted diet on weight loss, serum lipids, fibrinogen and vascular function in overweight and obese subjects. Methods Consumer study: One thousand nine hundred and ninety-seven South African individuals, randomly selected from metropolitan areas in South Africa, participated in this survey. Data were weighed to reflect the adult metropolitan population based on gender, age and race distribution. The total population (10 695 000) was representative of both genders (5 423 000 men and 5 272 000 women) and major race groups (2 615 000 whites, 6 252 000 blacks, 1 255 000 coloureds and 573 000 Indians) from different age groups and living standards. The questionnaires were designed by a multidisciplinary team and consisted of seventeen foodrelated questionnaires, of which one questioned the beliefs regarding avocados. Trained field workers administrated questionnaires by conducting face-to-face interviews with consumers. The market research company, MARKINOR, was contracted to collect the data. Quantitative data was statistically analysed in order to generate the relevant descriptive statistics, cross tabulations and statistical tests. SUMMARY Dietary intervention study: Sixty one free-living volunteers (13 men; 48 women), with a mean (standard deviation) body mass index (BMI) of 32 (3.9) kg/m2, participated in this randomised, controlled parallel study. The subjects were paired according to gender, BMI and age and randomly assigned to one of two groups. The experimental group consumed 200 g of avocado (1 avocado) per day, substituting 30 g of other mixed dietary fats, and the control group excluded avocado from their energy restricted diet for six weeks. Seven-day isoenergetic menu plans were given according to mean energy requirements of both genders to provide 30% fat, 55% carbohydrates and 15% protein of total energy intake. Anthropometric measurements, physical activity, dietary intakes, blood pressure and arterial compliance were measured with standard methods at the beginning and end of the intervention. Fasting blood samples were drawn at the beginning and end of the intervention period. Results Consumer study: There were no practical significant differences in the consumers responses in terms of gender or age. Practical significant differences were found between different race and LSM (Living Standard Measure) groups for some variables. The overall response of consumers towards the effect of avocados on health, heart health, children's health and the health effects associated with the fat content of avocados were very positive. However, almost half the consumers are still not convinced of or are uncertain as to the cholesterol content of avocados, while 47% of the consumers still believe that avocados are fattening. More than 80% of the consumers agreed that avocados are a good source of vitamins and minerals, and 76% consider avocados to be a good source of fibre. Almost 70% of the consumers agreed that avocados are good for sportsmen and -women. Avocados were seen by 49% of the consumers to be an aphrodisiac. Dietary intervention study: Fifty-five subjects completed the study. Compliance with avocado intake in the experimental group was 94.6%. Anthropometric measurements (weight, body mass index and percentage body fat) decreased significantly in both groups during the study (p<0.001), and the change was similar in both groups. Serum lipid levels (total cholesterol, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol and triglycerides), fibrinogen, blood pressure and arterial compliance did not change significantly within or between the two groups. SUMMARY Conclusions Consumer study: There are still a few myths and misconceptions that exist among some consumers regarding avocados, especially with regard to sexual functioning, cholesterol content, and fattening effect of avocados. The agricultural industry can use these results to plan different marketing campaigns focused on certain target groups to change the misperceptions concerning avocados and convey the positive nutritional value of avocados. Dietary intervention study: The consumption of 200 g avocado per day, within an energy restricted diet, does not compromise weight loss when substituted for 30 g of mixed dietary fat. The serum lipid levels, plasma fibrinogen, arterial compliance, as well as systolic and diastolic blood pressure were not affected by weight loss or avocado intake. / Thesis (M.Sc. (Nutrition))--North-West University, Potchefstroom Campus, 2004.

The avocado production and trade impose economic, social and environmental challenges for producers, and concerns for consumers. This ‘sustainability challenge’ will be analysed from a social- psychological viewpoint. The case study follows a two-method based approach: a combination of qualitative and quantitative research. Laws and restrictions on the avocado production in Mexico exist, still, avocados are not sustainable. The reasons are unveiled by a closer look into the trade agreements and by interviews with the Mexican civil society. The responsibility for the implementation of controls on sustainable avocados is pushed in a circle from the governments to civil society and back. Ideas on how to change the system are mainly based on EU citizens. Can a greater knowledge and awareness of EU citizens improve the sustainable avocado production in Mexico? The survey reveals that only few participants are fully informed and highly interested in eco-friendly produced avocados. The low percentage can be explained through the high costs for certified avocados, the mistrust in the certification system and the lack of the certified fruit in the supermarkets. However, after some background information the participants stated that they would change their behaviour: buying certified avocados, spending more money and going to special supermarkets. To raise awareness and clarify doubts, civil society in Mexico suggested campaigns in cooperation with civil society in the EU. The idea for the campaign is based on behaviourist theories. A further step is a cooperation between EU citizens with civil societies from Mexico and the EU to pressure the government into a system change to support the offer of cheaper certified sustainable avocados in the EU supermarkets, and thus to raise the standards and controls for the avocado production.

This diploma thesis deals with the import operation of Mexican avocados into the Czech Republic. It is divided into three chapters. The first chapter defines the trade with agricultural crops and depicts its specifics as well as the global avocado market production and export with its key players. A special attention is focused on Mexico, which has primacy in both categories. The second chapter analyzes the avocado market in the Czech Republic, it studies the consumption trends, import history and our key business partners. It also contains a survey that explores the consumption habits of the Czech population. The third chapter is devoted to the actual import operation of organic avocados from Mexico and all its requirements from vendor selection, business documents, logistics and pricing.