| Rhynchostylis gigantea (Lindl.) Ridley is a typical tropical epiphytic orchid which belongs to Rhynchostylis of Orchidaceae. It is a renascent herb peculiar to East Asia, while in China only distributes in Hainan Province. Because of the compact plant type, numerous and colorful flowers, as well as the pleasant fragrance, Rhynchostylis gigantea has a high ornamental value and a broad application prospect. But in China, the information for its distribution, adnascent character, population size, structure and resource situation is still not particular. However, as the tropical agriculture expands quickly, the habitation of Rhynchostylis gigantea has been destroyed badly. As a result, its wild resource is endangered and urgent for protection. So an investigation and collection of its germplasm resources was carried out all around Hainan Island. Then using SRAP molecular labeling and morphology labeling, the genetic diversity of168samples collected from different habitations was analyzed respectively. The results are as follows:1. A general situation of the distribution and habitat characteristics of Rhynchostylis gigantea was got. The habitation character:Rhynchostylis gigantea grows mainly in cloughs or sparse forests which are draughty, humid and well-lighted. It is mostly adnascent to arbors, about0.5-15m above the ground level. While the host plants it’s adnascent to cover13families and15genera. And in the community it grows, the edificators are mainly Liquidambar formosana, Bischofia polycarpa, Bombax malabaricum, Mangifera indica, Vitex quinata and so on.2. The endangerment of Rhynchostylis gigantea was determined. It took us one year to carry out this investigation, covering two thirds of Hainan territory. Via investigation, only22wild populations totally was found, and in every population the plant amount is rather small, so as the percentage of seedlings. Its amount has been dropped sharply in a short period, with the habitation being destroyed by artificial or natural cause and habitat scope becoming narrower. Therefore, the population now presents a disperse distribution. According to China Plant Red Book, the endangered category of Rhynchostylis gigantea has reached Category Vulnerable, and is transiting to Category Endangered.3. The SRAP-PCR reaction system of Rhynchostylis gigantea was established and optimized. Using orthogonal design and single factor experiments, we got the optimum system (20uL):template DNA60ng-(20uL-1), Mg2+2.0m mol-L-1, primers1.0u mol-L-1, TaqDNA1.5U·(20uL-1), dNTPs0.20m mol·L-1.4. Rhynchostylis gigantea has an aboudant genetic divisity. The clustering results showed that most materials in one population inhabitation clustered together while few materials clustered to the ones from other population habitations.24primer pairs were screened out from100pairs of SRAP primer combinations, and the genetic diversity of168copies of Rhynchostylis gigantea was analyzed. Using24pairs of primer combinations,390loci was tested out, including299polymorphic sites which occupies76.9%of the total amplification loci and shows abundant genetic diversity. The total bands amplified by each primer combination are10-24, while the average is16.2. Among these, the polymorphic bands are6-19, averagely12.5. It’s worth noting that by primer combination Me-8Em7, we amplified the most bands as well as the most polymorphic bands. By testing168materials, the genetic similarity coefficient was found to range from0.486to0.959, and the mean is0.694. Using software NTSYS-pc2.10and by means of COMPLETE, the clustering analysis for Rhynchostylis gigantea was done. At the level that similarity factor is0.51, these168materials tested can be divided into two groups. While at the level of0.60, the two groups can be divided into six subgroups. The clustering results showed the phenomenon of cross clustering, which indicated that the correlation between genetic distance and geographical distance is not close.5. The morphological characters of168gerplasm were observed and the oanamental value of109germplasm was estimated. We found that the variable coefficients of each morphological character are relatively high. There were two types of leaves:one is wide and long, while the other is narrow and short. What’s more, the floral structures such as the labellums, middle sepals, side sepals and petals all have various variation type. Sorting these morphological characters according to the variable coefficients, we got the order as follows:the average blooms on each inflorescence> the average length of each inflorescence> the average length of leaves> the average width of leaves> the average width of middle sepals>the average width of petals>the average width of labellums>the average length of middle sepals> the average length of petals> the average width of side sepals> the average length of side sepals> the average length of labellums. On the basis of20mophorlogy indices and using software SAS v9.0,109flowering Rhynchostylis gigantea germplam were clustered. And when the Euclidean genetic distance was1.25, these germplasmcan be divided into two groups, similar to the clustering results by SRAP labelling. At the same time,15plants with excellent ornamental traits were selected. |
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