INTRODUCTION.

Introduction Cassava was unknown to the Old World before the discovery of America. There is archaeological evidence of two major centers of origin for this crop, one in Mexico and Central America and the other in northeastern Brazil. the first Portuguese settlers found the native indians in Brazil growing the cassava plant. and Pierre Martyr wrote in 1494 that the "poisonous roots" of a yucca were used in the preparation of bread. It is believed that cassava was introduced to the western coast of Africa in the sixteenth century by slave merchants. The Portuguese takes it to the mouth of the Congo River, and then spreads it to other areas. in 1854 Livingstone described the preparation of cassava flour in Angola, and subsequently Stanley described its use in the Congo. cassava cultivation increased after 1850 in the east African territories as a result of the efforts of Europeans and Arabs who were pushing in the interiors and who recognized their value as a safeguard against the frequent periods of famine. in the Far East. cassava was not known as a food plant until 1835. In about 1850 it was directly from Brazil to Java, Singapore and Malaya. When the more profitable rubber plantations started on the Malay peninsula, cassava growing moved to other parts of Indonesia. during the period 1919-41 about 98 percent of all cassava flour was produced in Java, but during the Second World War, Brazil increased and improved its production. now grown throughout the tropical world, cassava is second only to the sweet potato as the most important starchy root crop of the tropics. Manihot utilissima Pohl of the family Euphorbiaceae. in recent publications, however, the name Manihot esculenta Crantz is being adopted.the plant is popularly known under a great variety of names: ubi kettella or kaspe (Indonesia), manioca, rumu or yucca (Latin America), mandioca or aipim (Brazil), manioc (Madagascar and French-speaking Africa), tapioca (India , Malaysia), cassava and sometimes cassada (English-speaking regions inAfrica, Thailand, Sri Lanka).The term cassava (manioc in French-speaking countries) is usually applied in Europe and the United States of America to the roots of the cassava plant, while tapioca-type products are baked products of cassava flour. the word tapioca derives from tipioca, the tupi indian name for the meal which expresses itself from the liquid expressed in pellets called tipiocet. Because it grows easily, has large yields and is not affected by diseases and pests? the areas under cassava are growing rapidly. The plant is grown for its edible tubers, which serve as a staple food in many tropical countries and are thus the source of an important starch. Its value as a famine relief crop has long been recognized. in parts of the Far East during the Second World Many people survived on cassava roots, and in Africa. It is now grown as a food crop or for industrial purposes. in many regions of the tropics cassava occupies much of the same position as the white potatoes do in some parts of the temperate zones as the principal carbohydrates of the daily diet. The industrial utilization of cassava roots is expanding every year. in the early decades of this century, cassava was held responsible for the rapid exhaustion of forest clearings, but later experiments in many parts of the tropics showed that it is not a soil-depleting crop. Since the Second World War, a more balanced appraisal of the crop has developed. more scientists, agriculturists and sociologists have become aware of their importance in developing countries, where it is most commonly produced. In many countries there is a focus on research for the improvement of production and utilization of cassava crops. 1. Cassava cultivation the plant The cassava plant is a perennial that grows to a height of about 2 4 m. The large, palmate leaves ordinarily have five to seven lobes borne on a long slender petiole. They grow only towards the end of the branches. as the plant grows, the main stem forks, usually into three branches which then divide similarly. The roots or tubers radiate from the stem just below the surface of the ground. Feeder roots growing vertically in the soil from the storage roots penetrate the soil to a depth of 50-100 cm. this capacity of the cassava plans to obtain a nourishment from the surface. Male and female flowers in loose plumes are produced on the same plant. the triangular-shaped fruit contains three seeds which are viable and can be used for the propagation of the plant. The number of tuberous roots and their dimensions vary among the different varieties