FOOD AND HEALTH BENEFITS OF LIVINGSTONE POTATO

Food is a primary need of living organisms. It provides adequate energy to do the biological and physical work. The early man explored his surroundings to locate the materials of natural origin for food. Still they continued their search in the plant and animal kingdoms to expand his food basket, but due to pontification in few crops and limited land for agricultural, a important problem has been created in last few years i.e. providing appropriate food for increasing populace at alarming rate of the world. Researchers are working day-night for achieving the appropriate food requirement at root level, still need appropriate plan/policies to get the optional food in near future. There are about 1500 wild edible plants available in the world and many of them are found in Nigeria, whereas only very few crops are cultivated as crop and frequently used as food. In, Nigeria, numbers of wild/ underutilized crops is used by the rural and tribal communities. They cultivated in home garden/ near to forest / collect from the forest, store and they used as food staples in day-to-day  as well as in critical periods. Those wild / underutilized crops are rich in nutrients and secondary metabolites. There are many  important food crops are found in Nigeria.  Among them, Plectranthus esculentus is important wild tuber crops belonging to family Lamiaceae. It is indigenous tropical crop to Africa and easily available in Nigeria and others Sub-Saharan African countries (Ukpabi, 2009).

          It is very popular as “Livingstone potato”. Plant was first cultivated in the upper Niger valley of the Hausaland in Nigeria and in the Central African Republic; although it is seen as a lost crop of Africa and it was cultivated since pre-historic times. It is a crop that is still relevant today. Tubers of the P. esculentus are quite important as rich of nutritious components and eaten as a substitute for potato (Solanum tuberosum). Tubers covered with thin layer as well as small size which make it difficult peeling. For this reason, difficult to get reasonable amount of yield. The farmers or gathers, who are mostly rural women use traditional systems for peeling i. e. applying friction with or without sharp sand in a flowing streams. The system is known as abrasion method of peeling (Ap). Botanically it is  Plectranthus esculentus is a perennial dicot herb  that is a member of the mint family . This herb can grow to be as tall as 2 metres. Some of the branches on the base bend down and grow into the ground that then can form oblong tubers, which are the fleshy underground stems. These tubers are edible and nutritious, often eaten as a substitute for potato or sweet potato. Although they are rarely seen because the vegetative reproduction is predominant, the plant also has yellow flowers. These flowers are two-lipped, and are on the short and crowded branches. While the plant is in flower the stems are leafless. Plectranthus esculentus has fleshy leaves, on angular stems. These leaves have brown gland-dots underneath and toothed edges. The tubers of this plant are quite important since that is the part of the crop that is used for sale, and farmer exchange.

Food, medicinal and economic values

The tubers of Plectranthus esculentus are often used as a substitute for a potato  or sweet potato. Directly after cultivation it can be boiled or roasted. The stems have been used to sweeten gruel (porridge). The leaves can be cooked in saucers as well. Plectranthus esculentus has been said to help with digestive problems also used to treat stomach ache and abdominal pain. It has also been used as anthelminthics. The fleshy underground stems, the tubers are the part of the plant that is consumed. This tuber crop is considered to be superior to other tuber crops in terms of its food value. In 100g there is:

• Crude protein level: 13 g
• Total lipids: 0.6 g
• Total carbohydrates 80 g
• Calcium 140 mg
• Iron 50 mg
• Vitamin A 0.17 mg

It is rich in carbohydrates, vitamin A, minerals, and essential amino acids. Plectranthus esculentus has contributed significantly to rural diets. In 2001-2002 farmers were able sell 250 g of this crop for up to Rand 5 (US$1), which is higher than the price of an Irish potato. Communities can also sell the cooked leaves for Rand 7 (US$1.30). There is this cash demand for Plectranthus esculentus but it is typically exchanged between neighbours and friends. Women have high knowledge of this crop including nutritious value and cultivation practices because it is indigenous. This is an advantage for farmers since they have the initial knowledge to grow this crop and the potential to be successful in the first season of harvest.

Research needs
Collecting and evaluation of Tsenza varieties would be the first step in germplasm research and development for improved production of the Livingstone Potato. This would be followed by development of techniques for rapid multiplication and distribution of improved varieties. Research on agronomic practices, pest and disease control, nutritional studies, post-production handling and processing will also be done. A project on Tsenza has been initiated at the Horticultural Research Centre, Marondera, Zimbabwe to improve food security and income-generation for rural communities through the maximum utilization and conservation of P. esculentus. More research activities will follow the germplasm-collecting exercise which has already been undertaken in Seke, Nyanga and Makoni some of the major production districts in the eastern regions of Zimbabwe. Similar activities are being undertaken in Malawi and South Africa, countries that together with Zimbabwe form a network whose vision is to have P. esculentus recognized as a valuable food crop. Through this network and in close collaboration with other countries, the vision on the Livingstone Potato may be realized and P. esculentus will attain the merit and status it deserves.