The Genetic Variation Of The F₁ Generations Of The Double Cross Hybrids Of Dendrobium Officinale

Agronomic characters based on the field experiment, the contents of polysaccharides and alcohol-soluble extracts of 18 F1 generations of double cross hybrids of Dendrobium officinale were studied in this paper. This paper aims to analyze the variation of agronomic characters, the contents of polysaccharides and alcohol-soluble extracts of F1 generations of double cross hybrids. The results were showed as follows:1. The differences in agronomic traits which included plant height, shoots number, basal sh oot diameter, shoot diameter, blade length, blade width, the ratio of blade length and width, roo t length and root number of the F1 generations of the Double cross hybrids of Dendrobium offi cinale were significant during seedling period.(9×66)×(78×69) have a great degree of variation i n agronomic characters, plant height, shoots number and the ratio of blade length and width we re the biggest number.(78×69)×(9×66)have a great degree of variation in agronomic characters, plant height, root number, the ratio of blade length and width and root length were the biggest number.After the comprehensive comparison of the metric of heterosis and the result of cluster analysis, The results showed as follows, the F1 generations of double cross hybrids growth exuberant, an d 10 combinations’ plant height, basal shoot diameter, shoot diameter and root length were su perior to mid-parent value. The percentage of the superiority combinations was 55.6%. The impact s of the cross and back cross on F1 generations of double cross hybrids were the difference of pl ant height, root length and root number.2. The differences in agronomic traits which included shoots number, plant height, stems diameter, internodes number, internodal length, blade length, blade width of the annual plants of the F1 generations of the Double cross hybrids of Dendrobium officinale were significant. Besides, all of the annual plants’ s shoots number and stems diameter were superior to mid-parent value. There was a great degree of variation in agronomic characters, plant height, shoots number and internodal length were the biggest number. After the comprehensive comparison of the metric of heterosis and the result of cluster analysis, the paper finds that, the annual plants of the F1 generations of double cross hybrids growth exuberant, and 8 combinations’ shoots number, plant height, stems diameter and leaf number were superior to mid-parent value. The percentage of the superiority combinations was 50.0%. The impacts of the cross and back cross on the annual plants of F1 generations of double cross hybrids were the difference in shoot number and stem diameter. Compared with the agronomic traits at seeding stage, the difference in plant height become non-significant, the difference in shoot number and stem diameter become significant.Then the paper further validated seedling selection had its boundedness and its instability.3. The differences in the contents of polysaccharides and alcohol-soluble extracts among the the F1 generations of the Double cross hybrids of Dendrobium officinale were significant. There were 11 combinations’ contents of polysaccharides and alcohol-soluble extracts were superior or equal to the mid-parent value. The impacts of the cross and back cross on the F1 generations of double cross hybrids’ contents of polysaccharides were significant. The average value of the polysaccharides contents of(78×69) ×(9×66) was 29.15%, and the average value of the polysaccharides contents of(9×66) ×(78×69) was 20.26%. The reciprocal cross was 8.89 percent higher than cross. This result showed that double cross can be an effective approach to select generations which had higt contents of polysaccharides and alcohol-soluble extracts, and had important implications for the selection of new Dendrobium officinale varieties by choosing parents with excellent comprehensive characters.