IOSR Journal of Environmental Science, Toxicology and Food Technology (IOSR-JESTFT) e-ISSN: 2319-2402,p- ISSN: 2319-2399.Volume 8, Issue 12 Ver. I (Dec. 2014), PP 54-57 www.iosrjournals.org www.iosrjournals.org 54 | Page Species of microorganisms associated with decayed tubers of Irish potato in storage in Plateau State, Nigeria. Istifanus, M.F. 1 , Ogbonna, A.I. 2* , Sila, M.D. 2 and Ogbonna, C.I.C. 2 1 Department of Microbiology, Plateau State University Bokkos, Jos, Plateau State, Nigeria. 2 Department of Plant Science and Technology, University of Jos Plateau State, Nigeria. Abstract: An investigation was carried on species of microorganisms associated with decayed tubers of Irish potatoes in storage in Plateau State, Nigeria. Three batches of decayed potatoes were collected from three different storage depots: Bokkos, Bukuru and Jos. The decayed portions of potatoes from each of the three experimental batches were aseptically cut out from the non-decayed areas of the potatoes with the aid of sterile blades. It was mixed up and further divided into two 2 halves. Each half of the experimental samples was plated out on Nutrient Agar (NA), Malt Extract Agar (MEA) and Potato Dextrose Agar (PDA) using serial dilution and soil plate methods. The resultant culture plates were incubated at 25±2 o C and examined after 24-48 hours for the development bacteria and yeast colonies and after 4-7 days for the presence of fungal colonies. A total of thirty-nine (39) species of microorganisms made up of eight (8) species of bacteria, three (3) species of yeast and twenty-eight (28) species of fungi were isolated from the decayed potato tubers. The genera that had the highest microbial species included Aspergillus, Lactobacillus and Fusarium. The isolates also contained mesophilic, thermotolerant and thermophilic species. The implications of the results obtained in terms of potato production in Nigeria have been discussed. Keywords: Associated, Bokkos, Bukuru, Jos, Irish potato, Malt Extract Agar (MEA), microorganisms, Nutrient Agar (NA). I. Introduction Root crops are produced mainly in the humid equatorial areas and the sub humid savannas adjacent to the equatorial zone [1]. The Irish potato, although native to highland equatorial tropics in the Andean altiplano, has been developed most successfully as temperate crop and is recently returning to the tropics. The production of this crop has increased greatly in recent times and has surpassed yam and sweet potato together, doubling in the last decade. Much of this increase has been in highland tropics, not only in the original home of the crop in South America but also countries such as Kenya, India and Nigeria. Irish potato is a complete food that is high in carbohydrate, protein and vitamins contents. It also contains some minerals such as potassium, phosphorus, iron and magnesium. It has about 70% water [2]. It is characterized by its large brown oblong shape. It is green in colour when it is not matured and yellowish brown when matured. It grows underground and develops from the swollen, underground stem of the plant. It grows best in climates where cool nights alternate with warm day especially during the period of tuber formation. It requires a growing temperature of 15 o C – 20 o C. In view of its nutrient and water contents, it is easily colonised by microorganisms especially when the skin is physically damaged due to harvesting faults which occurs under humid condition as reported by Donna [3]. Food decay is any undesirable change in food that causes it to loose its aesthetic value. Food is also said to be decayed when the original nutritional value, texture and flavour of the food are tempered with through the activities of microbial deteriogens. Generally, decay is the process in which the nutritional constituents of food are hydrolysed to the point that it is no longer acceptable to humans. Various factors could be responsible for the deterioration of various foods including Irish potato. The decay of potato could stem from physical damage as a result of dehydration. It could also happen as a result of long storage in the soil where it is in direct contact with soil microorganisms and the soil is known to be the reservoir of biodeteriogens. Potato decay could also be initiated by mechanical damage caused by insects and rodents. Such mechanical injuries on the potato easily lead to eventual colonisation by microorganisms. In the developed world, the Irish potato has many industrial and food uses. It could be processed into starch and alcohol [4]. Irish potato is almost exclusively eaten fresh in the developing countries. For nearly 20- 30 years the Irish potato was restricted to the highland tropics and was confined to use by privileged economic groups, especially the expatriates. Against this background potato merchants afforded refrigerated storage methods because the production was exceedingly low. This pattern still exists in some areas of the world. Irish potato is fast becoming staple food of many people and countries. Nigeria, Kenya and highland India are of particular interest as the potato is fast becoming quite widely accepted as a subsistence crop as well as a crop for sale at high prices for luxury markets.