Spoilt sweet potato tuber samples bought from Ogbete main market Enugu were used for this study. The isolation study and pathogenicity test were carried out. The result shows that the spoilage of sweet potato tubers was caused by fungi. The fungi isolated were Aspergillus sp, Rhizopus sp, Fusarium sp, and Phoma sp.
1.0 INTRODUCTION 1
1.1 AIM OF THE STUDY 7
2.0 LITERATURE REVIEW 8
3.0 MATERIAL AND METHOD 12
4.0 RESULTS 18
4.1 TABLE 1 22
4.2 TABLE 2 23
5.0 CONCLUSION 25
REFERENCES 29
Sweet potatoe (ipomoea batatas l) is root tuber crop belonging to the family convolvulaceae. It is an energy rich carbohydrate food. It thrives very well in moderately warm climates. It requires a growing period of at least four months of warm weather. The crop is grown extensively in Nigeria, especially in northern part. Sweet potatoes are one of the major subsistence crops in Nigeria. According to Olakesuisi (2004) root and tubers refers to any grown plant that stores edible materials in the roots, corms or tubers.
The total world production exceeds 140 million metric tones grown on 16.6 million metric hectares with yields of 0.86 metric tones per hectares. Estimates, of annual world production are 133m tones as compared with yam which has18m. tones. The largest producer of the crop is China. Other leading producing countries of the crop includes Japan, Taiwan, Indonesia, Korea, Brazil, Nigeria and Ivory Coast. Sweet potato is a root crop which is believed to have originated in Central America and was introduced to Africa probably at the end of 19th century. It is a tropical crop with China producing 85% of the world total while Africa accounts for just 5% (Awojobi 2004). The plant is now widely grown as an important staple food in a number of Africa countries including Burundi, Rwanda and Nigeria among others (Awojobi 2004).
Root and tuber crops are most important in Nigeria since they are major food crops and supply much of the carbohydrate requirement for normal health. The intensive hand operations which are needed to produce yams have made the growing of cassava and sweet potatoe more attractive to some farmers because of lesser labour they require for their growth.
A well recognized fact about this crop is that, it is an economical crop which provides a source of low-cost energy to the human diet as compared to other root and tuber crops. Sweet potatoe are mainly used as food after, boiling, baking, roasting or frying and the leaves equally serve as vegetable. The fresh sweet potatoe contained 25.95% starch which is even low but falls within the range reported by Li et al (1994). There was a general decline in starch content with storage period and according ray and Ravi (2005) respiration and transpiration contribute to weight loss and alteration of internal and external appearance of the potatoes. Because starch is used as respiratory substrate, the starch content decrease during storage and subsequently the dry matter also decrease.
In Nigeria, the vines form useful dry forage crop for ruminants and are of value for supplementary feeding during dry season. The leaves are edible and are eaten. They also serve as feeds for cattle, pigs and goats. They are good source of vitamins A and B. yellow and purple varieties is rich in carotene, thiamine, riboflavin, niacin and ascorbic acid.
The appropriate composition of a mature tuber is water 50 – 80, percent, carbohydrate 10 – 40 percent, fat 2-6 percent, the sugar content varies 0.5 – 6 percent. The mineral constituents are: calcium, magnesium, potassium, sodium, phosphorus, chlorine, sulphur and iron.
Various traditional method of sweet potato storage such as heap storage, plat form and pit storage method have been practiced in Nigeria and across African countries by farmers. Pit storage of sweet potato has been reported in Indonesia, Zimbabwe and Malawi by Woolfe (1992) and in Nigeria by Awojobi (2004). Pit storage can generally be considered to be cheap for the rural communities since it is less expensive.
In the face of the present food situation in Nigeria, one of the major obstacle to food production is that of storage. During harvesting seasons tubers crops are very much available at cheap prices but this availability is usually short lived due to storage problems. Tropical crops suffer tremendously due to inadequate storage practices. Sweet potatoe as crop suffer most from this problem when compared to other roots and tuber crops. Nigeria farmers under their local practices have the problem of storing the tuber over a period of time after harvest. These problem are those originating from:
Report have shown that local farmers in Nigeria in the effort to minimize too much loss Nigeria in the effort to minimize too much loss of their harvested tubers, practice the following methods of storage to check the problems they encounter
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