Studies On The Evolution And Taxonomy Of Mustard (Brassica Juncea (L.) Czern.et Coss.)

Chinese mustard (Brassica juncea Czern et Coss.) is one of the important vegetables originated from China. Classification of mustard had been conducted for almost one century. But the views are different and controversial. The classification and genetic relationship of Chinese mustard were studied based on morphological traits, pollen scanning electron microscope and AFLP analysis by using the representative cultivars of different mustard subspecies. It forms a very useful guide not only for investigating the relationships among different mustard genotypes, but also in the selection of parents for hybrid breeding and sexual cross breeding.Cluster analysis based on morphological characteristics, including leaf, seed, flower and special organs, such as root, stem, leaf, bolt, showed that all 17 mustard cultivars used in this experiment could be cluster into 5 groups, i.e. leaf mustard, stem mustard, root mustard, bolting mustard and seed mustard. Cultivars in each group were similar in morphological traits, especially in their modified organisms.Pollen grains of 17 mustard subspecies were examined under scanning electron microscope (SEM). Result showed that the pollen shapes were near spherical, or spheroidal, or super-spheroidal in equatorial view, varied with mustard cultivars. The pollen grain size changed greatly among subspecies, but it was rather difficult to classify the subspecies, according to the pollen grain size. However, by comparison of the sculpture of pollen extine and germinal pore, as well as pollen shapes and pollen size, mustard subspecies used in this experiment could be classified. This classification could comparable to the traditional subspecies classification.Cluster analysis result based on morphological characteristics was comparable to that obtained from pollen scanning electron microscope, especially in stem mustard. But the results in leaf mustard were quite...