Master of Science

A study of the cost of production of crops is important for the farming interests of any county or state. Much is now being written on the subject of economic marketing but economic production is just as important. No matter how good a marketing plan may be, if there is a leak in the production, no farming operations can be really successful. The question of economic production is for the individual farmer to answer, and to aid him in solving this problem, a study of the cost of production must be made by the individual and state. Any states which have carried on production studies have found such studies a great help to the grower in planning his crop production. However, there are many states which have not made any such studies at all. The data for the following article was obtained mostly by writing to the different Experiment Stations in the United States. Little could be obtained from the Agricultural Library of the Virginia Experiment Station which shows the need for this kind of work here. In fact, none of the data pertaining to Virginia crops was obtainable from this source. This article will be, as far as possible, a comparison of the cost of production of corn, wheat, hay and potatoes in Virginia with the same crops grown in other states and sections of the United States. In this comparison it will be determined whether it is possible for Virginia to compete with these regions in the production of these crops. / Master of Science

Yeast breads were prepared with three levels of mashed sweet potato pulp and of mung bean flour. Nine combinations of mashed sweet potato pulp (10, 20, 30 percent), and of mung bean flour (4, 8, 16 percent) substitutions for wheat flour were used to determine the acceptability of these enriched breads. Added liquid was adjusted for moisture in sweet potato pulp. Sensory evaluation data was analyzed by analysis of variance to determine the major effective factor on the acceptability of bread. Objective measurements were used to determine bread volume, percent crude nitrogen, percent ether extractable crude fat, and moisture content of the breads. The sensory evaluation results indicated that the bread quality decreased with increase in the amount of mung bean flour; mashed sweet potato pulp did not affect the bread quality except that the highest level (30 percent) has a slight adverse effect on bread texture. The characteristics of all breads made with mashed sweet potato pulp and mung bean flour varied with the amount of substitute ingredient. In general, mung bean flour affected the acceptability of bread and bread quality. Breads made with 20 percent mashed sweet potato pulp and 4 or 8 percent mung bean flour were judged to have more desirable eating quality. Volume of bread was decreased with increase in the amount of mung bean flour and of mashed sweet potato pulp. The percent crude nitrogen increased with the addition of mung bean flour and decreased with the addition of mashed sweet potato pulp. Bread enriched with 16 percent mung bean flour and 10 percent mashed sweet potato pulp increased in the amount of percent crude nitrogen approximately 16.7 percent compared with the control. Percent ether extractable crude fat content of all breads was low and was varied. Moisture content increased with addition of mung bean flour and mashed sweet potato pulp. / Master of Science

Sweet potato single-leaf cuttings of cultivars ‘Centennial,’ ‘Jewel,’ and ‘Nemagold’ were planted in plastic pots containing steam-sterilized sand. Fully opened leaves were counted from the terminal apex on stock plant stems, and leaf positions 1 to 3 and 7 to 9 were referred to as mean leaf positions 2 and 8 respectively. Dry weight and its partitioning among plant organs (leaf, stem, petiole, new shoot, fibrous roots, and stronger roots) differed among the three cultivars. ‘Centennial’ had the highest storage root dry weights in both the first (December-March) and second (April-June) experiments. The new shoots and storage root dry rates of ‘Centennial’ and ‘Jewel’ were 3 to 25 times greater at 79 days after planting (DAP) in the second experiment than at 70 DAp in the first experiment. The new shoot was the dominant sink in ‘Nemagold’ between 28 and 70 DAP in the first experiment but not in the second experiment, and the storage root never became a strong sink in either experiment. A shift from leaf dry weight increases to decrease was observed in the first experiment but not in the second experiment. Leaves in mean leaf position 2 showed higher original plant material (leaf, petiole, and stem) dry weight than mean leaf position 8, but there were no significant differences in final storage root dry weight between these two mean leaf positions in both experiments. Mean leaf positions 2 approximant net assimilation rate (NAR) values based on leaf and new shoot dry weight exceeded mean leaf positions 8 approximate NAR values in both experiments. Plants with stem attachment had higher new shoot and storage root dry weights than plants without stem attachment. Dry weight of the original leaf decreased in plants with steam attachment but not in plants without stem attachment. / M.S.

The present study analyzes the economic impact of the introduction of Genetically Modified Organisms (GMOs) in Uruguay's agriculture. Using a partial equilibrium framework the impacts of transgenic varieties are simulated for two crops, rice and potatoes, in small open and closed economies respectively. The model accounts for the presence of market imperfections created by the monopolistic behavior of the genes' patent owner. The change in economic surplus generated after the adoption of the new technology is projected to be positive, although the seed markup charged by the monopolist reduces the surplus compared to a perfectly competitive market. Total deadweight losses and domestic losses are found to increase with the seed premium, as additional monopolist profits are extracted out of the country. Adoption decreases with the seed premium, further reducing the domestic consumer and producer surplus. The results of the study suggest an active role for national technology policies and for the agricultural R&D system in Uruguay to generate conditions that attract the technology's owner to a small market while at the same time reducing the potential losses that monopoly power creates . / Master of Science

Monoploid genotypes (2n = x = 12), derived by anther culture of a diplandrous genotype of Solanum phureja, a South-American diploid potato species, were examined for their utility in germplasm development. Nine monoploid genotypes and the diploid anther-donor plant were grown in photoperiod chambers at The Southeastern Plant Environment Laboratories (SEPEL) at North Carolina State University to examine the effect of photoperiod on tuber yield and to determine the variability for critical photoperiod for tuberization. Significant differences were found among the monoploid genotypes for total tuber weight and tuber number. Longer photoperiod treatments both decreased and delayed tuberization. Axillary tuber formation from single-node cuttings was used to estimate the onset of tuber induction and demonstrated variability among monoploid genotypes for critical photoperiod for tuberization. Leaf-disc culture of 24 monoploid genotypes yielded calli which regenerated plants from three genotypes. SDS-polyacrylamide gel electrophoresis of leaf extracts demonstrated variability among diploid and tetraploid calliclones of one monoploid genotype for total protein banding pattern. Absence of stainable pollen and lack of seed set after crosses to diploid species and tetraploid cultivars illustrated infertility among doubled (2n = 2x = 24) and twice doubled (2n = 4x = 48) monoploid-derived lines. Flow-cytometric analysis of pollen obtained from the diploid anther-donor genotype grown under three photoperiods at SEPEL yielded two populations of pollen based on propidium iodide staining of DNA. These populations corresponded to pollen separation based on size parameters alone, introducing the potential for flow sorting of pollen to increase seed set in 4x-2x crosses to tetraploid cultivars. Protoplast isolation from in vitro material and extraction of leaf nuclei both in vitro and in vivo were performed on the anther-donor plant, one of its anther-derived monoploids, and a diploid and tetraploid plant derived from callus culture of the monoploid genotype. Flow-cytometric analysis of propidium-iodide Stained cells and nuclei showed a greater ploidy stability for plant material grown in vitro and a limit to endopolyploidization imposed by initial ploidy level. Flow-cytometric analysis of protoplast-derived nuclei from nine monoploid genotypes derived from anther culture of a single diploid genotype exhibited Significant differences for 4C DNA content, but not for 1C DNA content, indicating that ploidy stability, rather than monoploid status per se, is influenced by genotype. / Ph. D.

Since sweet potatoes, which also furnish vitamin A, are a common food in the popular diets of Texas and are so generally grown over the state, the purpose of this study is (1) to ascertain the amount of vitamin C in eight of the varieties most commonly grown and (2) to determine the effect of the three most popular methods of cooking (boiling, baking, and candying) on the vitamin C content of these varieties of sweet potatoes.

The purpose of this study was to determine by biological method of assay the vitamin A content of Puerto Rico sweet potatoes which were dehydrated immediately after harvesting.

The object of this paper is to determine the optimum concentration of sulfur dioxide to be used in the commercial dehydration of the sweet potato by this process. Attention has been given to two aspects of the problem, (1) the effect of sulfur dioxide upon the extraction of water from the sweet potato by mechanical means, and (2) the effect of sulfur dioxide upon the stability of the carotene in the sweet potato over a period of several months.

Graduation date: 1995