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The Virginian variety and four selections of the Porto Rico variety were planted on two soil types at Toano, and Walkerton, Virginia, and on one soil at Warsaw, Virginia. At Williamsburg, Virginia, the Virginian, Nancy Hall, and a selection of the Porto Rico were planted under aluminum foil mulch, black paper mulch, and on cultivated plots. From these plantings an attempt was made to determine the influence of aluminum foil mulch, black paper mulch, selection or variety, and soil type, on the factors studied. The following summary is given of the results obtained from the “Mulched Treatments” phases of the experiment: 1. Aluminum foil mulch tended to increase the soil moisture and lower the soil temperature as compared to black paper mulch end cultivation. 2. Where the entire plot was covered by unperforated black paper, without some provision for water to reach the soil, the soil moisture is lowered. 3. The carotene content of the Virginian was 3 to 4 times as high as the Porto Rico variety. 4. Neither the yield nor the carotene content of the Porto Rico variety was affected by the aluminum foil, or black paper mulches. 5. The carotene content and yield of the Virginian, and the total yield of the Nancy Hall was higher under aluminum foil mulch than on the cultivated plots. 6. There was no difference between the aluminum foil, black paper, and cultivated treatments in the smoothness and uniformity of shape of the three varieties considered. 7. The Virginian was smoother and more uniform in shape than the Porto Rico or Nancy Hall varieties. The Virginian was also more uniform in skin and flesh color than the Porto Rico variety. The following summary is given of the results obtained from the “Affect of Variety and Selections” and “Affect of Soil Type” phases of the experiment: 1. No variety or selection was consistently higher in yield than all the others. 2. Selection #2 of the Porto Rico variety was the only selection which was consistently among the highest in yield at all locations. 3. The Virginian sweet potato variety was smoother and more uniform in shape than any of the selections of the Porto Rico. 4. No selection of the Porto Rico variety was consistently smoother than the others. Selection #1 was the most consistent selection of the Porto Rico variety to grade high in uniformity of shape. 5. There was no appreciable difference between varieties and selections in their disease susceptibility. 6. No selection or variety was significantly better, in respect to cracking, than the others. 7. The Virginian variety was 3 to 4 times as high in carotene content than any of the selections of the Porto Rico, regardless of location or soil. It was also more uniform in skin and flesh color. 8. None of the selections of Porto Rico was consistently higher in carotene content. Selection #4 varied more than the other selections in the uniformity of skin color. 9. Variety or selection was a more important factor than soil type in determining the yield, carotene content, and uniformity of flesh, and skin color of the sweet potatoes. 10. Soil type did not affect the yield of the Virginian, or selections of Porto Rico at either of the locations. 11. Soil type had only a slight and inconsistent affect on the smoothness, and uniformity of shape of the sweet potatoes. 12. Under the conditions of this experiment there was no consistent difference in soil type in the amount and kind of disease present. / Master of Science

Text in English / Potato is an important source of energy to most micronutrient malnourished affected population in South Africa. Improvements through bio-fortification can therefore enhance access to essential micronutrients. The study was aimed at determining the level of variability of iron and zinc concentration among 20 potato genotypes as a preliminary step for future breeding program. The materials were evaluated using inductively coupled plasma optical emission spectrometry. Statistical analysis indicated significant (P<0.001) variation of Fe and Zn among the genotypes. The average concentration ranges from 34.67 to 76.67 mg kg-1 and 12.88 to 66.1 mg kg-1 for iron and zinc respectively. The best performing genotypes were cultivar Mnandi, Hertha, Buffelspoort and breeding lines-N105-1, 00-S100-33 and 03-627-50. Iron concentration was positively correlated with Zinc concentration. The study showed that enough variability of Fe and Zn concentration exist among the evaluated genotypes, which can be exploited for use in potato bio-fortification breeding programme. / Agriculture, Animal Health and Human Ecology / M.Sc. (Agriculture)

Potato is an important source of energy to most micronutrient malnourished affected population in South Africa. Improvements through bio-fortification can therefore enhance access to essential micronutrients. The study was aimed at determining the level of variability of iron and zinc concentration among 20 potato genotypes as a preliminary step for future breeding program. The materials were evaluated using inductively coupled plasma optical emission spectrometry. Statistical analysis indicated significant (P<0.001) variation of Fe and Zn among the genotypes. The average concentration ranges from 34.67 to 76.67 mg kg-1 and 12.88 to 66.1 mg kg-1 for iron and zinc respectively. The best performing genotypes were cultivar Mnandi, Hertha, Buffelspoort and breeding lines-N105-1, 00-S100-33 and 03-627-50. Iron concentration was positively correlated with Zinc concentration. The study showed that enough variability of Fe and Zn concentration exist among the evaluated genotypes, which can be exploited for use in potato bio-fortification breeding programme. / Agriculture, Animal Health and Human Ecology / M.Sc. (Agriculture)