Study On Genetic Diversity Of Brassica Juncea In Tibet

The objective of this program was to make clear the genetic variation between wild B.juncea and cultivated B.juncea in Tibet by means of morphology, cellular and SSR analyses. The main results obtained are as follows:1 Morphology analysesIt had been found that morphology of B.juncea in Tibet was very rich and wild B.juncea was more abundant in cultivated B.juncea by analyzing of growth habit, cotyledons, basal leaf, elongation leaf, Stem leaf, flower, silique and agronomic characters.2 Cellular analysesThe chromosome number of B.juncea in Tibet was found to be 2n=4x=36, but the build up of chromosome type were different from different regions. In addition, B.juncea in Tibet lacked satellite. The difference of karyotype features showed specificity of B.juncea in Tibet at cell level.3 SSR analyses3.1 Expansion effectDifferent primers brought about very different number of alleles, and the most gene was nine, the least was one. In addition, some scarce alleles were found out.3.2 Polymorphic loci ratio of SSR66 polymorphic site were amplified by SSR markers, 3.30 Polymorphic loci of every primer, and Polymorphic loci ratio is 95.65%. Genetic diversity of B.juncea in Tibet is very significant, and wild B.juncea was more abundant in cultivated B.juncea at molecular level.3.3 Genetic diversity, polymorphism information content, coefficient of gene differentiation and gene flowThe average Genetic diversity at SSR markers for four populations was 0.515 1, and the average polymorphism information content was 0.420 1. this explained that genetic diversity was high, among B.juncea in Tibet, S.arvensis, relative species3.4 Cluster analysisAt Tv= 305.49, four populations were distinguished, except Pengbohuang. At Tv=103.26, the test materials were classified into eight Subgroups which cultivated B.juncea in Tibet were classified into two Subgroups and wild B.juncea were classified into four Subgroups. Presentation of clustering resulted geographical variation and eco-environment had important influence on genetic diversity of B.juncea in Tibet, and showed B.juncea in Tibet had abundant genetic variation under given loading conditions. There had been more rich in warm cool semi-arid mountainous shrub district in Western Tibet and mountainous warmth semi-arid shrub district in central Qinghai Xizang Plateau especially.