CHAPTER ONE
INTRODUCTION
1.1 Background of study
Sweet potato (Ipomoeabatatas (L) lam) is grown in more than 100 countries in tropical, subtropical and temperate climate. It ranks as the world’s seventh most important crop, with an estimated annual production of approximately 122 million metric tons
Sweet potato is a major staple food in African, Asia the Caribbean and South America, where they are important sources of carbohydrate, vitaminA and C, fiber, iron,potassium and protein (Wolfe, 1992).
Sweet potato belongs to the family convolvulaceae and originated from South America from where it was introduced to usually consider the only species of Ipomoea of economic important. In developing countries, sweet potato is especially valued because it is highly adaptable and tolerates high temperate, low fertility soil and drought.Sweet potato is also used as animal feed, which has been a byproduct of crops grown for human consumption. It is the only crop among the root tuber crops that had a position per capita annual rate of increase in production in sub-Saharan Africa.
Increasing recognition of the great potential of the sweet potato crop as a nutritious food for humans and animals has resulted in intensified research efforts to enhance production and consumption in recent decades (Woolf, 1992, Yamakawa and Yoshimoto, 2002).The plant is an herbaceous perennial vine, being alternate heart-shaped or palmately lobed leaves and medium-sized sympetalous flowers.
The edible tuberous root is long and tapered, with a smooth skin whose colour ranges between yellow, orange,red, brown purple and beige. Its flesh ranges from beige through white, red pink,violet,yellow,orange and purple.
I.batatas is propagated vegatatively as the seeds are heterogeneous and used only for breeding purposes.In tropical countries where the crop can be grown year-round, the crop is usually propagated by replanting vine cuttings from the preview crops. In temperate countries, the crop is usually grown in a nursery for field transplantation at the beginning of the summer.
The origin and domestication of sweet potato is through to be in CentralAmerica, however,some generally agree that it originated in North America where many more varieties are found there.
Research to identify accessions high in different nutritional qualities(dry matter,protein,starch,sucrose,B-carotene,Fe,Zn,Ca and Mg ) has been initiated by the
center for international potato(CIP), for germplasm in gene bank and breeding