ABSTRACT. PCR-amplified DNA using the random primer OPB-06 was used as a probe for Fluorescence in situ hybridization (FISH). Signals of hybridized sites were observed in both interphase and metaphase plates after hybridization. The FISH signals of the metaphase chromosomes were confirmed as two yellow-color signals hybridized with the probe on two adjacent loci at interphase of the control plates. FISH analysis of the metaphase plates of 25µg/ml deoxynivlenol (DON) and aflatoxin B 1 (AFB 1 ) treated plants revealed 85.7% and 89.3%, respectively had no signals. Of the metaphase plates of plants treated with AFB 1 , 3.6% had one terminal signal while 7.1% revealed two signals and no signals were observed in 89.3% plates. Regarding the interphase nuclei, only one signal was observed in 42.1% of the plates where two signals were observed in 57.8% interphase plates. 10.7% metaphase plates of plants treated with DON had one terminal signal while 3.6% exhibit two signals and no signals were observed in 85.7% plates of metaphase. 44.1% of the interphase nuclei had one signal while 53.2% plates reveal two signals and four signals were observed in 2.7% interphase nuclei. Disappearance of FISH signals in some metaphase plates of plants treated with the two investigated toxins indicates the toxigenic effect of these mycotoxins on metaphase chromosomes of wheat.

ABSTRACT. Based on the cytological and molecular studies, types and frequency of chromosomal aberrations during meiotic division of wheat plants treated with different concentrations of deoxynivalenol (DON) were investigated. The common types of abnormalities that have been recorded were stickiness, outside, laggards, bridges, fragments, unequal division, as well as multipolar and micro-nucleated cells. Regarding the first meiotic division, the percentage of abnormal cells detected from untreated plants was 2.12% however, plants treated with 5, 10, 15, 20 and 25µg/ml DON revealed 3.73, 6.62, 6.78, 9.23 and 8.18% of abnormalities, respectively. In the second meiotic division, control plants exhibit 2.69% of abnormalities while, 2.29, 4.34, 4.23, 5.59, 4.46% of abnormal cells were detected from plants treated with 5, 10, 15, 20 and 25µg/ml DON, respectively. These results demonstrate the significant effect of treatment with DON on the total percentage of irregularities during meiosis. DNA amplification patterns of wheat plants treated with DON using two RAPD primers revealed some variations in the DNA profiles within the examined samples as compared with the control. Such variations include band intensity and appearance of novel bands or disappearance of others. The polymorphism of the detected DNA fragments particularly the absence of a number of fragments in some plants treated with different concentrations of DON suggested that contaminated wheat grains with this toxin or mycotoxigenic fungi might induce DNA rearrangements, deletions and/or changes in the DNA sequence that lead to the observed changes.