Survey of the Post Harvest Diseases and Aflatoxin Contamination of Marketed Orange Fruit (Citrus Sp.) In Major Cities in Oyo State, Nigeria

Abstract

Survey and collection of the marketed orange fruit with rot symptoms were conducted in the South Western Nigeria in 2011 and 2012 respectively. Orange fruits showing rot symptoms that are displayed for sale in five different market places in five major cities in Oyo State in South Western Nigeria namely, Ogbomoso, Oyo, Saki, Ibarapa and Ibadan were collected and examined for the presence of the inducing pathogens as well as aflatoxin contamination. Fourteen pathogenic fungi were isolated from rotted orange fruits were: Aspergillus flavus, Aspergillus niger, Botryodiplodia theobromae, Botrytis cinerea, Curvularia lunata, Fusarium oxysporium, Fusarium moniliforme, Geotrichum spp., Penicillium citrinum, Penicillium digitatum, Rhizopus stolonifer, Trichoderma viridae, Phytopthora spp and Rhizopus nigricans. A. flavus, A. niger, F. oxysporium, F. moniliforme, Geotrichum spp, P. digitatum, P. citrinum and R. nigricans respectively had the significantly (P≥0.05) highest rate of occurrence among the isolated fungi while Trichoderma viridae and Curvularia lunata were significantly (P≥0.05) least encountered in this study. Pathogenicity tests revealed that of all isolated fungi, Aspergillus flavus, Fusarium oxysporium, Rhizopus nigricans, Fusarium moloniforme, Geotrichum spp., Penicillium citrinum and Rhizopus stolonifer were highly pathogenic with the first three leading to rapid disintegration of treated fruit in 3-5 days, while the rest were moderately pathogenic with the exception of P. oxalicum and T. viride that caused the least significantly pathogenic rot of orange fruits. Quantities of aflatoxins were detected from infected orange fruits, collected from all the markets in each city in