Bioengineering and Bioscience 3(5): 90-94, 2015 http://www.hrpub.org DOI: 10.13189/bb.2015.030503 Fungi Associated with the Deterioration of Post-harvest Onion Bulbs Sold in Some Markets in Awka, Nigeria Onuorah Samuel 1,* , Obika Ifeanyi 2 1 Department of Applied Microbiology and Brewing, Nnamdi Azikiwe University, Nigeria 2 Department of Zoology, Nnamdi Azikiwe University, Nigeria Copyright © 2015 by authors, all rights reserved. Authors agree that this article remains permanently open access under the terms of the Creative Commons Attribution License 4.0 International License Abstract Onion bulbs rots are caused by microorganisms especially fungi leading to economic loss. These fungi have been known to produce toxins which are injurious to human and animal health, therefore in this study, the fungi associated with the spoilage of onions bulbs purchased from Umuike, Amaikwo, Amaudo, Okpuno and Permanent site markets were isolated, characterized and identified. The average fungal counts ranged between 1.2 x 10 3 CfU/ml and 2.0 x 10 3 CfU/ml. The fungi isolated from the spoilt onion bulbs were Penicillum digitatum, Fusarium oxysporum, Rhizopus stolonifer, Alternaria alternata, Aspergillus niger and Saccharomyces cerevisiae. The samples from Amaudo market had the highest percentage distribution of fungi of 34.2% while those from permanent site had the least percentage distribution of 8.6%. Aspergillus niger had the highest percentage distribution of 34.29% in the spoilt onion bulbs while Saccharomyces cerevisiae had the least percentage distribution of 5.71%. Aspergillus niger also had the highest rot diameter of 40mm while Saccharomyces cerevisiae had the least rot diameter of 16mm. Adequate mycological knowledge, storage facilities and handling practices would therefore minimize the deterioration of onion bulbs thereby ensuring its availability to the society all year round. Keywords Fungi, Deterioration, Post-harvest, Onion Bulbs, Markets 1. Introduction Onion (Allium cepa L.) is an important vegetable crop in Nigeria based on consumption and economic values to farmers. It is one of the most important and familiar spice crops throughout the world. The crop is grown for its bulbs which are harvested in most countries once a year and are used daily in every home for seasoning and flavouring of foods. Onion is a valuable ingredient in the diet due to its content of sugars, vitamins, minerals, electrolytes, proteins and dietary fibre [1-3]. Numerous benefits have been attributed to onions including prevention of cancer and cardiovascular disorders, reduction in the blood levels of cholesterol, reduction in osteoporosis, reduction in stomach ulcers, inhibition of the proliferation of cultured ovarian, breast and colon cancer cells, inhibition of platelets-mediated thrombosis, prevention of inflammatory processes associated with asthma, treatment of fever, common cold, cough, sore throat and its use as an antimicrobial agent [4, 5]. Onions are packed locally in baskets and jute bags. These packaging materials come from palm, bamboo and fibrous jute trees. However these materials provide no barriers of dust, and can easily be crushed which might lead to damage of the onions. During storage, some losses occur due to sprouting, drying and rotting [6]. Bulb rots are a common cause of onion loss during storage. They are caused by microorganisms particularly fungi. The black mould disease caused by Aspergillus niger is a limiting factor in onion production worldwide [6]. Aspergillus niger has been reported to survive between onion crops as a soil saprophyte in or on bulbs in field or storage and is ubiquitous in nature. The fungus invades bulbs of onions in field or storage whenever they find injured tissues by producing various enzymes or toxins [7]. Association of Aspergillus niger with onion seeds produced in hot climates and their transmission from soil and naturally-contaminated seeds to onion seedlings cause 30-80% loss or spoilage of onion bulbs. The deterioration of raw onions may result from physical factors, actions of their own enzymes, microorganisms or a combination of these factors. Mechanical damage resulting from actions of animals, birds or insects or from mishandling may predispose towards increased enzymatic action or entrance and growth of microorganisms. Previous damage by plant pathogens may make the part of the crop used as food unfit for consumption or may open the path for the growth of saprophytes and spoilage by them. Contact with spoilage onions may bring about the transfer of organisms causing spoilage and increasing their wastage. Unfavourable