Genetic Diversity Of Orychophragmus Violaceus (Cruciferae) In China

Orychophragmus violaceus belongs to Orychophragmus genera of Cruciferae family, which is widely distributed in China. It is an optional ground covering plant with high utilization value in food, forage, health care and gardening. O. violaceus will be a mode plant for it has many advantages for the genetic analysis including the simple genetic background, short life cycle, prolific seed production and easy reproduction. In order to discuss correlation of morphological variation and genetic variation and find out the internal mechanism for the morphological variation, we analyse the biological characteristics of O. violaceus and studied the genetic diversity of populations from different regions on three levels: the morphological characters, karyotypes and molecular. These results could offer reference information for its future breeding, culture, and classification of infra-species. The main results obtained were as follows:1. The biological characterstics of O. violaceus was studied, including its phenophase of blossoming and bear fruit,the pollen activities, the stigma receptivity, breeding system and the seed germination characteristics. The results showed that the florescence was from late March to middle May, and the full-bloom stage was in April. The single flowering stage could last about 5 days. The fruit ripening was in early Jule. The activity period of pollen was from the bud time to 4th days. But the stigma receptivity testing showed that the best time of pollination was 3rd day and 4th day after flowering. So it was difficult for O. violaceus to accomplish self-pollination in nature conditions. Two grads changes were designed to test the germination of seed, one was the temperature change, 20℃, 25℃, 30℃;Another was the different year of gathering the seed, 2003, 2004, and 2005. The conclusion showed that the fresh seeds had highly germinated in 25℃. 2. We sampled seven populations from Beijing and Nanjing and selected 34 morphological characters. The results showed that the stem height, stem and inflorescent ramification are multiform in difference habitats, and therefore have little taxonomic value. The variations of the leaf shape, leaf margin and the leaf hair are consecutive in population, indicating that they are unreliable for taxonomy. The variation of flower, including color, size and form of petal, are more steady and discontinuous in population, showing high taxonomic value. The analysis of variation and multiple comparisons of the 17 numerical characters suggest that, in the same year, most of these characters are significantly different among populations, which, on contrast, are inconspicuous between the localities. However, in different years, they are inconspicuous among populations. Finally, we analysed seven populations and 30 characters using numerical taxonomic method. Q cluster reveals that the three populations from the Summer Palace, Zijin Mountain Park and Zhongshan Botanical Garden of Nanjing are grouped together and so do the other four populations. The R cluster shows that flower, leaf, and the characters involving the hair and color of plants are grouped together, and so do the characters involving growth volume.3. The karyotypes of four populations from Beijing, Houbajia Nursery, the Temple of Heaven, the Summer Palace, and Yuanmingyuan Park, were studied. The results showed that: (1) through observation of the number of somatic chromosomes, we find that the ingredient of somatic was intricate. The majority of the somatic chromosomal number of O. violaceus is 2n=2x=24. The karyotypes of these four populations are as followed: Houbajia Nursery 2n=2x=24=4sm+20m; The Temple of Heaven 2n=2x=24=24m; The Summer Palace 2n=2x=24=6sm+18m; Yuanmingyuan Park 2n=2x=24=24m. (2) High percentage of B chromosomes was observed in the nucleus, and the number is 1, 2 and 3. (3) Euploid and aneuoloid were also found in these populations including the number of 5, 6, 8, 9, 12, 13, 14, 15, 18, 19 and 20. The above mentioned results indicated that the chromosomals of O. violaceus appeared considerable hereditary variation during the phylogenetic process of species.4. The genetic diversity of 245 individuals from 9 populations of O. violaceus in China was investigated using inter-simple sequence repeat (ISSR) markers. A total number of 162 bands were amplified by using 8 ISSR primers chosen for the study, of which 150 were polymorphic loci, which indicating pronounced genetic variation at the species level. A relatively high level of genetic diversity was also revealed: PPB=93.59%, He=0.4242,I=0.6103 (at species level); PPB=87.02%,He=0.3464,I=0.5150 (at population level ). The result of Nei′s GST analysis was 0.1643. The analysis of molecular variance (AMOVA) showed that the genetic variation was mainly found within populations was 80.80% and variance among populations was 16.43% and among groups was 2.77%. The gene flow among populations (Nm) was 2.5760. UPGMA cluster analysis which according to genetic similarity indicated that 9 populations were clustered into 3 groups. The 4 populations from Beijing region grouped together, whereas 5 populations from Nanjing and Shanghai clustered in two groups which didn't differentiate obviously. The differentiation among O. violaceus populations was not found in the study.We conclude the following from our investigation using the three assessment approaches: (1) O. violaceus is widely distributed in in northeast, northwest, north, and east and mid of China and has long florescence which was from late March to middle May. This specie belongs to cross-pollinate plants whose pollinate spreaded mainly through wind and insect. (2) There is a large amount of genetic diversity in O. violaceus germplasm resources. The variation within populations, which is significantly higher than that between populations, was the main causes that result in variation of O. violaceus germplasm resources. (3) The differentiation among populations of O. violaceus is smaller because of its reproductive biology and large gene flow, and so smaller was between regions. (4) The UPGMA analysis also indicated that there was no distinct genetic differentiation between geographical regions. But resources from the same region were closer than that from different regions.