الفهرس 
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Abstract
Genus Brassica L. out family Brassicaceae is one of the most agronomically essential genera, the family containing about 80 species globally. In Egypt, the genus exemplified by 5 species. Among them, Brassica nigra (L.) Koch, which grows as a weed in field crops as well as roadsides of Mediterranean region.
B. nigra possesses a unique importance as one of the two evolutionary lineages in genus Brassica and as one of the three pillars of the famous diploid Brassica Triangle. The field and herbarium observations reflecting notable morphological diversity within the wild species populations in Egypt. The taxonomic identity of these variations not resolved yet. Accordingly, morphological, palynological, cytological and molecular studies for the different geographical populations of Brassica nigra were carried out to trace the species diversity and helps for identification the infra-species taxa.
The taxonomic revision of the species in Egypt, was carried out on the herbarium specimens as well as fresh materials represented by 26 populations, distributed along the Nile Valley and the Nile Delta. The results revealed the presence of two varieties namely var. bracteolata and var. nigra. The fruit beak and trichomes are the differential morphological characters delimiting the two varieties. Moreover, the results show also presence of var. nigra in two different biotypes.
SEM examination of the seed coat and pollen grains showed the presence of notable infra-specific diversity. For pollen grains, the size, apertures and exine ornamentation confirming this diversity.
In spite of the morphological diversity, chromosome numbers are similar (2n=16) in all the studied taxa representing the diploid Brassica B genome (BB), but the karyotype showed highly variable chromosomes, referring to their mean relative length (MRL) and mean centromeric index (MCI), karyotyping also indicating the presence of satellite in the chromosome pair no. “6” which characterizes var. bracteolata from var. nigra. This observed variability indicating that each taxon retains its genotypic identity.
Molecular characterization of the studied populations using nuclear marker (ITS) and chloroplast markers (rps, ropC1 and trnK introns) indicating the molecular variation between the morphologically distinct varieties (var. nigra & var. bracteolata), These results support us to treat these morphological forms as distinct varieties not as synonyms.
The study revealed the importance of the multidescriptive approach in biosystematic studies.
Finally, we conclude that the autotaxonomy of B. nigra in Egypt based on the macro- and micro-morphological characters, cytological and molecular studies confirming the presence of two distinctive varieties var. nigra and var. bracteolata with a trend in phylogeny within them and these two varieties should adopted taxonomically. So, we made taxonomical key for differentiation between different biotypes of Brassica nigra.