Analysis of microbial growth medium of sweet potato(Ipomoea batatas)
Chapter One
1.0 Introduction
Sweet potato (Ipomoea batata) is a dicotyledonous plant which belongs to the family convolaceae, among the approximately 50 genera and more than 1,000 species of this family, only Ipomoea batata is a crop plant whose large, starchy, sweet tasting tuberous roots are an important root vegetable (purseglove 1991; Idooife, 1992). Sweet potato is a tuberous plant. The edible tuberous root is long and tapered with a smooth skin whose color ranges between red, purple, brown and white, its flesh ranges from white through yellow, orange and purple. (Edimond and Ammermam, 1970). The young leaves and shoots are sometimes eaten as green. The sweet potato is only distantly related to the potato (Solanum tuberosum).
It is commonly confused with the yam in parts of North America, although they are not even distantly related to the other plant widely known as yam in the Dioscoreaceae family, which is native to Africa and Asia. In most of the United States, the soft, sweet orange variety is called yam. (The genus Ipomoea that contains the sweet also includes several garden flowers called morning glories, through that term are not usually extended to Ipomoea batata. (Gore and Reed, 1973).
Sweet potatoes are rich in complex carbohydrates, dietary fiber, beta carotenela vitamin A equivalent nutritional, vitamin c and vitamin B6. In 1992, the center for science in the public interest compared the nutritional value of sweet potatoes to other vegetables, considering fiber content, complex carbohydrate, protein, vitamin A and C, iron and calcium, the sweet potato ranked highest in nutritional value.
Sweet potato varieties with dark orange flesh have more beta carotene than those with light encouraged in Africa where vitamin A deficiency is a serious health problem. Despite the name preliminary studies on animals have revealed that it insulin resistance. Sweet potato yields an important starch which is used commercially in laundries in sizing textile and papers and in manufacturing adhesives.
The root tubers are most frequently boiled fried, or baked. They can also be processed to make starch and a partial flour substitute. Industrial uses include the production of starch and industrial alcohol. In some tropical areas, they are staple food crop. (Asiedu, 1989).
The plants (sweet potatoes) are now cultivated throughout tropical and warm temperate regions wherever there is sufficient water to support their growth. The plant does not tolerate frost. It grows best at an average temperature of 240c (750f), abundant sunshine and warm nights. Annual rainfalls of 750-1000mm are considered most suitable with a minimum of 500mm in growing season.
The crop is sensitive to drought at the tuber initiation stage 50-60 days after planting and is not tolerant to water-logging, as it may cause tuber rots and reduce growth of storage roots if aeration is poor. Depending on the cultivars and conditions, tuberous roots mature in two to nine months. Early-maturing cultivars can be grown as an annual summer crop in temperate areas, such as the northern United States. They are mostly propagated by stem or root cuttings or by adventitious roots called slips that grow out form the tuberous roots during storage.
True seeds are used for breeding only. Colder temperature injures roots of sweet potato. They grow well in many farming conditions and it has few natural enemies. Pesticides are rarely needed. Sweet potatoes are grown on a variety of soils, but well drained light and medium textured soils with a pH range of 4.5-7.0 are more favourable (Kulkarni, 1994). They can be grown in poor soils with little fertilizer. However, sweet potato are very sensitive to a lumilium toxicity and will die about 6 weeks after planting if lime is not applied at the planting in this type of soil (woolfe, 1992).
Sweet potatoes are believed to have originated in North and South America and spread throughout the tropical America into the carribean and across the South pacific to Island. Some sweet potatoes are grown for export, mainly to Japan. China grows over 100 varieties of sweet potato. After the introduction, sweet potato became popular in Islands of the Pacific Ocean, from Japan to Polynesia. The general Polynesia word for sweet potato is kumara and the South American word is kumar (keane and Beltron, 1986).
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