ABSTRACT
Fruits are one of the most important agricultural products that supply the body with vitamins and essential minerals elements, but it is contaminated by fungi during the period of growth, harvesting and storage. A. niger is one of the species that grows on the fruit during the period of storage, and secretes mycotoxins especially ochratoxin A. This study was conducted with the purpose of isolating and identifying different strains of A. niger from 20 samples of pear collected from Taif markets and to determine the ability of these strains to produce OTA. It was observed that showed that out of 20 pear samples collected, 19 samples were detected to be contaminated with different strains of A. niger and the strains were able to produce OTA. From 27 isolates of A. niger which was used to test the ability of production OTA, 10 strains only produced OTA. The range of OTA in all strains were 0.18 to 9.5 ppb. Representative 27 strains of ochratoxigenic and non ochratoxigenic black Aspergilli isolated were subjected for detection of ochratoxin biosynthesis genes, by using two sets of primer for two genes involved in ochratoxin biosynthetic pathway. Bands of the fragments of PKS15C-MeT and PKS15KS genes visualized at 998 and 776 bp, respectively. Whereas, the presence of four tested genes is not sufficient marker for differentatin between aflatoxigenic and non aflatoxigenic isolates.