Please read the abstract in the section, 00front of theis document / Dissertation (MSc (Agric) Food Science and Technology)--University of Pretoria, 2008. / Food Science / MSc / Unrestricted

Since Pre-Colombian time corn already formed part of the diet in Aztec and Mayan cultures, and actually represented in them a fountain of wealth and power. The cultivation is utilized in the region in multiple forms, not only for the human diet, but also as feed for animals. Corn is third place in the world production, following wheat and rice. It is cultivated in a total surface of 106 million hectares, its yield is 215 million tons, that represents an average of 2 tons per hectare. The cultivation of corn has special importance, given that this cereal constitutes the basic food the Latin-Americans. This cereal adapts extensively to diverse ecological conditions. Its high performance and future possibilities of even more improvement through genetics make this cereal one of the plants most promising to confront the threat of hunger in the world. For this reason, it is cultivated in almost every part of the world because of its ample range of elevations. It can grow from sea level to approximately 2500 meters. In the last few years, the world production of corn has grown an average of 3.2% per year, set against 1.1% of semi-annual growth, for surface sown. This difference comes from a strong increase of the average unit yield. This was possible thanks to use of highly productive hybrid corn, with the aid of improve agricultural techniques, such as greater plantation density, more resilient, uses of more effective pesticides and herbicides, etc. In Bolivia, the agriculture area has large potential to develop, but because of political causes not appropriate for our country, and the insufficient economic resources that destines the area to stay rural, these negative aspects are responsible for the backward movement and the misery, making it impossible to develop the agriculture area. The region of Cochabamba, constitutes the main supplier of food. In the country, the economic activity of the valleys are based mainly in agriculture and stockbreeding, being characterized as a growing zone and basically for cereal, whose preferential scale of cultivation is as continues: Corn, wheat, barley, alfalfa, and other. The population of Cochabamba varies because of the growing of corn is only in the seasons of summer and part of the fall, the rest of the time few people stay there. The farmers, to obtain better prices, try to harvest at the start and end of the growing seasons, this is possible when they make a good management of plant's health, irrigation, and soil. etc., due to the smaller effort, the prices are higher, but in the months of February and March is when the effort pays off, because almost all of the farmers harvest, and the prices of this product drops, many times even below the price of production, being consequence of the dry culture. The price of fresh corn on the cob is greater than dry corn. When corn is fresh it has different uses such as humitas, lawas and corn on the cob. El Valle Alta (Punata), the farmers do not market their produce in the markets, despite of the small farms of the area, for this cause merchants truckers exist that gather the produce of all the farmers, and take the majority of the profits, which is why it is necessary for industrialization of the agricultural production. The vegetables are directly or indirectly the source of all the food, because they are capable of using solar energy and to carry out diverse chemical synthesis, that cannot be performed by animals. The principles of the same they are photosynthesis, which consists of the application of the solar energy, to synthesize carbohydrates, and the fixation of nitrogen, which is the foundation for the synthesis of the proteins. The vegetables most consumed are the cereals, legumes, and tubers, they constitute the basic diet. The word ""vegetable"" includes an extensive range of vegetables, and the majority of the vegetables contain at most 60%-80% of the water.

The present work was conducted in order to determine an adequate variety in the processing of small corn, in which a monitoring of all the cycle in cultivation was conducted. The behavior of the small corn was analyzed in the laboratory before the presence of three antioxidants, ascorbic acid, acetic acid and sodium sulfate in two concentrations in addition to subjecting them to thermal treatments that allows us to obtain a pleasant product for the consumer that is both resistant to treatment and nutritious for the health. The results indicate that the best variety of corn is muruchi yellow, the most effective antioxidant is sodium sulfate with a concentration of 1% and the thermal treatment of 10 minutes which obtained the best results, being most pleasing to those persons that evaluated the corn for its organic qualities followed by the ascorbic and acetic acid provided which provided a project of industrial feasibility that provides the information as a convenience to investment.

Quality protein maize (QPM) has enhanced levels of two essential amino acids, lysine and tryptophan compared to normal maize. This makes QPM an important cereal crop in communities where maize is a staple crop. The main abiotic factor to QPM production is drought stress. Little information is available on the effect of drought stress on QPM. Therefore, the objectives of this study were to: (i) conduct diversity analysis of QPM inbred lines using morpho-agronomic and simple sequence repeat markers, (ii) screen available QPM inbred lines and F1 progeny for tolerance to seedling drought stress, (iii) determine the combining ability and type of gene action of QPM inbred lines for tolerance to seedling drought stress, grain yield and endosperm modification. The study was conducted in South Africa, at the University of Fort Hare. Morphological characterisation of 21 inbred lines was done using quantitative and qualitative traits. A randomised complete block design with three replicates was used for characterizing the inbred lines in the field. Genstat statistical software, version 12 (Genstat ®, 2009) was used for analysis of variance (ANOVA) and descriptive statistics. Analysis of variance was performed on all quantitative data for morphological traits. Data for qualitative traits was tabulated in their nominal classes. Traits that contributed most to the variation were days to anthesis, days to silking, anthesis-silking interval, plant height, number of kernel rows, ear length and grain yield. Cluster analysis grouped the inbred lines into three main clusters. The first cluster was characterised by tall and average yielding lines, while the second cluster showed the least anthesis-silking interval, and had the highest yield. Cluster three consisted of lines that were early maturing, but were the least yielding. Genetic distances between maize inbred lines were quantified by using 27 simple sequence repeat markers. The genetic distances between genotypes was computed using Roger’s (1972) genetic distances. Cluster analysis was then carried out using the neighbour-joining tree method using Power Marker software version 3.25. A dendrogram generated from the genetic study of the inbred lines revealed three groups that concurred with expectations based upon pedigree data. These groups were not identical to the groups generated using morpho-agronomic characterisation. Twenty one QPM inbred lines were crossed using a North Carolina design II mating scheme. These were divided into seven sets, each with three inbred lines. The three inbred lines in one set were used as females and crossed with three inbred lines in another set consisting of males. Each inbred line was used as a female in one set, and as a male in a second set. Sixty three hybrids (7 sets x 9 hybrids) were formed and evaluated in October 2011, using a 6x8 alpha-lattice incomplete block design with three replicates under glasshouse and optimum field conditions. A randomised complete block design with three replicates was used for the 21 parental inbred lines. Traits recorded for the glasshouse study were, canopy temperature, chlorophyll content, leaf roll, stem diameter, plant height, leaf number, leaf area, fresh and dry root and shoot weights. Data for the various traits for each environment, 25 percent (stress treatment) and 75 percent (non-stress) of field capacity, were subjected to analysis of variance using the unbalanced treatment design in Genstat statistical package Edition 12. Where varietal differences were found, means were separated using Tukey’s test. Genetic analyses for grain yield and agronomic traits were performed using a fixed effects model in JMP 10 following Residual Maximum Likelihood procedure (REML). From the results, inbred lines that were not previously classified into heterotic groups and drought tolerance categories were classified based on their total dry weight performance and drought susceptibility index. Inbred lines L18, L9, L8, L6 and L3, in order of their drought tolerance index were the best performers under greenhouse conditions and could be recommended for breeding new varieties that are tolerant to seedling drought stress. Evaluation of maize seedlings tolerant to drought stress under glasshouse conditions revealed that cross combination L18 x L11 was drought tolerant, while cross L20 x L7 was susceptible. Total dry weight was used as the major criteria for classifying F1 maize seedlings as being resistant or susceptible. General combining ability effects accounted for 67.43 percent of the genetic variation for total dry weight, while specific combining ability effects contributed 37.57 percent. This indicated that additive gene effects were more important than non-additive gene action in controlling this trait. In the field study (non-drought), the experimental design was a 6x8 alpha lattice incomplete block design with three replicates. On an adjacent field a randomised complete block design with three replicates was used to evaluate the parental inbred lines. The following variables were recorded: plant height, ear height, ears per plant, endosperm modification, days to silking and days to anthesis, anthesis-silking interval, number of kernels per row, number of rows per ear and grain yield. General analyses for the incomplete lattice block design and randomised complete block design for hybrid and inbred data respectively were performed using JMP 10 statistical software. Means were separated using the Tukey's test. Genetic analyses of data for grain yield and agronomic traits were conducted using a fixed effects model using REML in JMP 10. The importance of both GCA (51 percent) and SCA (49 percent) was observed for grain yield. A preponderance of GCA existed for ear height, days to anthesis, anthesis-silking interval, ears per plant and number of kernels per row, indicating that predominantly, additive gene effects controlled hybrid performance under optimum field conditions. The highest heritability was observed for days to silking (48.27 percent) suggesting that yield could be improved through selection for this trait. Under field conditions, variation in time to maturity was observed. This implies that these inbred lines can be recommended for utilisation in different agro-ecologies. Early maturing lines such as L18 can be used to introduce earliness in local cultivars, while early maturing single crosses such as L18 x L2, L5 x L9, L3 x L4 and L2 x L21 could be recommended for maize growers in drought prone areas such as the former Ciskei. Single crosses L18xL11, L16xL18, L8xL21 and L9xL6 had good tolerance to seedling drought stress. On the other hand, single crosses L18xL11 and L11xL13 had high grain yield and good endosperm modification. All these single crosses could be recommended for commercial production after evaluation across locations in the Eastern Cape Province. Alternatively they can be crossed with other superior inbreds to generate three or four way hybrids, which could then be evaluated for potential use by farmers in the Eastern Cape.