Identification Chromosome Ploidy Of Dendrobium And Construction Of RAPD Molecular Genetic Maps

In this study, tow methods, i.e. chromosome flaking and flow cytometry, were used to identify chromosome ploidy of nobile-type Dendrobium. Besides, 90 hybrids obtained from controlled cross D. Lucky Gal 'Emito' and D.Fantasy 'Crown' as maping population and RAPD markers were used to construct the primary genetic linkage maps of Dendrobium. At the same time, an optimized Dendrobium RAPD assay technique were estabilished, and RAPD segregation and construction of molecular genetic maps were also discussed. The main results were as followed:1. Identification of the chromosome ploidy of DendrobiumFlow cytometric(FCM) analysis of ploidy level was made in 53 nobile-type Dendrobium cultivars and 26 species ,of Dendrobium. An unequivocal identification of diploids, triploids, and tetraploids as well as chimeras such as diploid plus tetraploid, and triploid plus hexaploid, and tetraploid plus octploid, was possible from their discrete peaks of histograms. Chromosome flaking was made in 17 varities and 4 species of Dendrobium The research results revealed that, there were not only diploids, triploids, and tetraploids,but also chimeras such as diploid plus tetraploid.Comparatively, using flow cytometry for identification of ploidy was ideal method because of simple preparation of sample, rapid and accurate measurement, though the results were different from chromosome flaking's, the method can be used for reference. Count chromosome number for identifying was considered to be the most trusty.2. Analysis of RAPD polymorphism between mapping populationAmong 420 random primers were tested, 90(2.4%) primers gave amplified bands in the parents. The 90 random primers revealed 215 highly polymorphic RAPD loci in F₁ population of these parents. By way of Chi-Square Test, 93(43.26%) departed from Mendelian segregation laws(1:1) from these polymorphic loci, while 122 polymorphic loci expected 1:1 segregation ratio.3. Construction of meloculer genetic maps of DendrobiumThe genetic linkage map of Dendrobium was built according to RAPD assays in our experiments.The map with a total length of 6568.7cm and average interval of 50.11cm had 121 markers distributed in 9 linkage groups. The length of the individual linkage groups ranged from 128.8cm to 1043.0cm and the number of marker in the individual linkage group is from 3 to 21.