Study On Brassia Campestris L.evolution In Tibet

From the germplasm resource of Brassia campestris L. in Tibet, the wild and cultivated germplasm resource were choosed in paper and morphology, cell karyotypes,SSR were analyzed to research the difference between the wild and cultivated and probe the evolution trend Brassia campestris L in Tibet. Main results got were as follows:1. Morphological study①Phenotypic character evolution: In the evolution process from the wild Brassia campestris L. to the cultivated Brassia campestris L., Growth habit in seedlings evolved from unitary to richness. The height of plant evolved from short to high. The color of elongation stem evolved from purple to green.②Radical leaf, stalk leaf, elongation stalk leaf and flower organs in the wild and the cultivated all evolved in same period as well as in different period. There were eight characters which evolved in different period, accounting for 25.81%. There were 17 characters which evolved in same period, accounting for 54.84%.2. Cytology studyThe chromosome number in apex cell of Brassia campestris L. in Tibet was 2n=20,the length of chromosome in wild was 2.83～4.85μm and that was 2.04～5.08μm in the cultivated.The total length of chromosomes in wild was longer than that of the cultivated. Ratio in the wild(1.71) between Length of the longest and that of the shortest chromosome was smaller than that of in the cultured(2.49). Karyotype formular in the wild Brassia campestris L. is 2n=2x=20=8m+2sm, The Symmetry extent was high. Karyotype formular in the cultivated Brassia campestris L is 2n=2x=20=10m+10sm, The Symmetry extent was low, belonged toⅡB.The Symmetry extent of Karyotype formular evolved from high Symmetry in the wild Brassia campestris L to low Symmetry in the cultivated Brassia campestris L.3. Molecular biology study①30 bands were obtained in the cultivated Brassia campestris L., average polymorphism rate was 75.0%, 35 bands were obtained in the wild Brassia campestris L., average polymorphism rate was 87.5% which was in excess of 12.5%,Genetic diversity of Brassia campestris L. evolved from richness to unitary. Using ANOVA,the difference between Wild Brassia campestris L. and cultivated Brassia campestris L. was significant.②Among all the Brassia campestris L. in Tibet,The genetic dispersion coefficient of wild Brassia campestris L. and genetic flow was higher than that of cultivated Brassia campestris L. but the coefficient of genetic differentiation.③At mahalanobis distance 129.3～256.4,Two groups were divided,The mahalanobis distance of one of groups wild Brassia campestris L. in Tibet was at 64.1～128.2,Ⅰ,Ⅱsub-groups could be divided. The mahalanobis distance of the other groups was at 64.1～129.3,Ⅲ,Ⅳsub-groups could be divided,it is indicated that the wild and cultivated rapeseeds existed obviously difference on genetic base.