Auto-taxonomy of Brassica nigra (L.) Koch (Brassicaceae) in Egypt.

Abstract

BRASSICA L. is one of the most economically important genera within family Brassicaceae, it includes approximately 80 species worldwide. In Egypt, the genus represented by five species. Among them, Brassica nigra (L.) Koch, which grown as a weed in field crops as well as roadsides of Mediterranean region. The field and herbarium observations reflected the notable morphological diversity within the species populations. Accordingly, morphological and palynological 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 peak and trichomes are the differential characters delimiting the two varieties. Moreover, the results showed also presence of var. nigra in two different biotypes. SEM 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. Photographs and taxonomic key for varieties and forms will be addressed.