The present investigation was carried out to study the cytological effects of the herbicide atrazine on Allium cepa and Vicia faba with respect to the cell cycle response , mitotic index, chromosome aberrations and nucleic acids content. The root of young seedlings of V. faba and adventitious roots of A. cepa were treated with the following concentrations: 25% , 50%, 75% and 100% of the recommended dose (3.75 g/l) for 4, 8, 12, 24 h. The results indicated that atrazine herbicide reduced the mitotic division in both plants compared to the respective control. Mitotic index values were progressively decreased with increased the concentration and treatment time. In V. faba, the treatment with the concentration of 100% for each treatment time (4, 8, 12, 24 h) was toxic , but in A. cepa, the same concentration with 24 h was only toxic. The percentage of the reduction in MI values in V. faba was higher than that in A. cepa. Also, it has been clearly observed that the inhibition of mitotic division was associated with reduction in DNA and RNA contents in both treated plants root tips. This may point out that the inhibition of mitotic activity is due to a deficiency of DNA in the nucleus. The increased percentage of prophase in both plants was accompanied by decreased percentages of the other mitotic phase. The total percentage of aberrations increased with the increasing the concentration of atrazine herbicide and the period of treatment. The total percentage of aberrations in A. cepa was higher than that in V faba for each treatment. Different abnormal mitotic figures were observed in all mitotic phases. Such types of abnormalities were stickiness , lagging, C-mitosis, bridges, irregular prophase, unequal distribution, fragments and a few cells with micronucleus at interphase stage.

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In the present study, molecular genetic fingerprints for 7 Raphanus L. samples belonging to 2 species (Raphanus raphanistrum L. and Raphanus sativus L.) were carried out to elucidate relationships among these samples. Extracted DNA from fresh leaf samples was used to identify the molecular fingerprints. Fifteen 10-mer arbitrary oligonucleotide primers were initially used to establish their randomly amplified polymorphic DNA based on polymerase chain reaction (RAPD-PCR) fingerprints and to discriminate among them. Only 6 primers successfully generated reproducible polymorphic products. These primers are; UBC 43, 51, 66, 71, 77 and 91. The fingerprints generated by these primers revealed characteristic profiles for each Raphanus L. genotypes, in terms of number and position of RAPD bands. The results revealed that both the number and size of the amplified products varied considerably with the different primers. A sum of 66 polymorphic bands was generated by these primers in the Raphanus L. genotypes under study. A total of 20 unique bands were identified out of the polymorphic ones. These unique bands were used to discriminate among the studied Raphanus L. samples. Most samples of the studied Raphanus L. samples were discriminated by one or more unique bands.The family CruciferaeϭBrassicaceae is a large natural family of major economic importance. Heywood (1993), recorded about 380 genera and 3000 species in this family, whereas, Mabberley (1997) reported the number of genera to be 365 and the number of species to be 3250. On the other hand, Judd et al. (1999) recorded 419 genera and 4130 species belonging to this family.Cruciferae is well represented in the Egyptian flora. Täckholm (1974) reported 61 genera and 106 species distributed in the different habitat types of the country. From them 5 species belonging to genus Brassica L. and only one species belong to genus Raphanus L. On the other hand, El-Hadidi and Fayed (1995) recorded 55 genera and 108 species for the family. Of these species, 5 were recorded for Brassica L. and 2 for Raphanus L.Development of cultivar-specific genetic markers is desirable for plant taxa identification and protection as well as seed purity determination. Moreover, knowledge of genetic diversity in economical plant gene pools is central to the development of effective ex-situ and in situ germplasm conservation strategies (Demissie and Bjernstad 1997, Wolff andMorgan-Richards 1998). Traditional cultivar identification based on morphological traits requires extensive observations of mature plants (Wrigley et al. 1987). Furthermore, morphological traits cannot serve as unambiguous markers because of environmental influences (Yang and Quiros 1993). Also, the adequate levels of phenotypic polymorphism are not available in many plant taxa (Tatineni et al. 1996). Nowadays, molecular markers have been developed to solve this problem. These markers are independent of environmental conditions and show higher levels of polymorphism. Several methods such as SDSprotein, isozymes and RAPD-PCR ban...