International Journal of Modern Botany: 2011; 1(1): 1-3 DOI: 10.5923/j.ijmb.20110101.01 Fungi Associated with Storage Rots of Onion Bulbs in Sokoto. Nigeria K. Shehu, S. Muhammad * Department of Biological Sciences, Usmanu Danfodiyo University, Sokoto. Nigerian Abstract A survey of fungi associated with postharvest deterioration of onion bulbs was conducted in Sokoto, north-western Nigeria in 2010. Rotten onion bulbs sold at five different markets: Sokoto central markets, Kasuwa daji, Gawon nama, Arkilla and Mabera were infected with eight species of fungi: Aspergillus niger, A. flavus, A. fumigatus, Al- ternaria porri, Rhizopus stolonifer, Fusarium oxysporum, and Penicillium citrinum. Of these, A.niger, A.flavus and A.porri were the most frequently isolated fungi. Penicillium citrinum was the least encountered fungus. Pathogenicity tests revealed that all the isolated fungi were pathogenic on onion bulbs however; A. porri, R. stolonifer and P. citrinum were the most pathogenic leading to rapid disintegration of the infected bulbs within 21 days of inoculation. While A. niger was the least pathogenic. The implications of the findings in relation to post harvest handling of onion bulbs and mycotoxin production were discussed. Keywords Onion Bulbs, Fungi, Storage Rots, Markets 1. Introduction The onion (Allium cepa L.) is an important vegetable crop in Nigeria based on consumption and economic value to farmers. The crop is grown for its bulbs which 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 and minerals (Ole et al., 2004). The crop is grown mainly in the north, during the dry season (October to April). The onion farmers in Nigeria almost always store, their onions after harvest for one to five months to ensure a con- tinual supply through seasons when fresh produce was un- available. Bulb rots are a common cause of onion loss during storage. Fungi, especially moulds are important pathogens of fruits and a vegetables particularly under tropical and sub-tropical conditions (Adebayo and Diyaolu, 2003 ).The importance of storage rots includes reduction in the quantity and quality of onion which affects the market value (Dogondaji et al., 2005). Other important consequence often overlooked, is mycotoxin contamination of the affected material (Muhammad et al., 2004). 2. Objectives Fungal contamination of onion bulbs constitutes menace in the production and storage of onion particularly in the * Corresponding author: samdiri@yahoo.co.uk (K. Shehu) Published online at http://journal.sapub.org/ijmb Copyright © 2011 Scientific & Academic Publishing. All Rights Reserved tropics. Apart from toxins production. Pressence of fungi on the onion bulbs eventually leads to disease development in the field when the infected bulbs are planted in the preceding cropping season. The objective of this paper was to isolate and identify pathogenic fungi associated with postharvest deterioration of onion bulbs in Sokoto, north – western Nigeria. 3. Material and Methods 3.1. The Study Area The study was conducted during the months of May to August, 2010 in the Department of Biological Sciences, Usmanu Danfodiyo University Sokoto. Sokoto State is one of the northern states where a large proportion of onion production and storage take place annually. The area is lo- cated in the north – western Nigeria (Longitude 3 – 9 ° East; latitude 10 – 14 ° North). It is characterized by long dry sea- son (October to April) and a short rainy season (May to September). Average monthly temperature ranges from 21 to 35℃ and is lowest in December and January. Heat is more severe in March and April. 3.2. Collection of Samples Onion bulbs showing symptoms of rotting and discolour- ation were randomly selected from five different markets: Sokoto central markets, Kasuwa daji, Gawon nama, Arkilla and Mabera located in Sokoto metropolis, for microbial analysis. 3.3. Isolation and Identification of Rot Inducing Fungi