| Dendrobium plants is a kind of important botanical resource which contains great value both in commercial use and scientific research.However, the species are facing great challenge because of over collection,destruction and reducing of their living area.Therefore,carring out the investigation of germplasm resources status and resources conservation work has important practical significance.In this paper,the germplasm resources of Dendrobium plants,the breeding system of D.loddigesii in Yachang Guangxi Orchid Nature Rreserve were studied and fungi strains from natural roots and pseudobulbs of D.loddigesi in Bawangling Nature Reserve in Hainan Province were isolated and inoculated into the germfree seedling of Dendrobium plants.The main results are summarized as the following: 1)It was made clear that how Dendrobium plants distributes in Yachang Guangxi and the factors endangering the species basically.According to the study,there were 8 kinds of Dendrobium plants growing in the area, D.aurantiacum,D.loddigesii,D.chrysanthum,D.hercoglossum,D.aphyllum,D.fimbriatum,D.lohohense and D.lindleyi.All the species were rare in holding.Although D.aurantiacum was the largest group among all the species, the amount was no more than 100 clumps either.The biological and ecological characteristics of Dendrobium plants in the area were fatal reasons leadind to their severe danger.Further more,the vanishing and the fragmentation of the growing environment caused by human activity were also responsible for the results.2)For D.loddigesii,the fruiting rate of natural pollination and two kinds of spontaneous self-pollination(bagging,not emasculation;bagging, emasculation)were 0,and for the cross pollination coming different plant, cross pollination in one plant and self-cross,the fruiting rate were 100.0%, 71.4%and 28.6%respectively.The results showed that D.loddigesii was opomictic,not self-pollination and needed appropriate pollinators for propagation.3)The isolation rates for the 14 samples varied a lot according to the same separation positions and the highest rate was 80%and the lowest one was 13.3%.There was no apparent difference in separation rate for different hosts in the root.The average separation rate was 43.7%for the root attached to rock,while the rate was 49.3%for the root attached to the stem of Liquidambar formosana.4)A total of 127 strains were isolated from the 14 samples and were merged into 30.Among all the 30 strains separated from the D.loddigesii, only 10%(3strains)of them showed promoting ability to D.loddigesii and D. hercoglossum(the code are 14,27 and 28).Otherwise,76.7%of the strains were harmful for their growth.5)For the D.loddigesii and D.officinale seedlings,the promoting ability of the strains and their combination(14-27,14-28,27-28 and 14-27-28) appeared differently.In addition,the strains did also show different strength on the same seedling under different growth indicators.Take the fresh weight as a standard,the promoting ability for D.loddigesii was 14-28＞14＞27,while 14＞27＞14-27 for D.officinale.When it went to the promoting ability on the height of the plants,the order was 14-28＞14-27-28＞27 and 28＞14＞27-28. For the promoting of tiller number,the order was 14-28＞14-27-28＞27-28 for D.loddigesii.However,only 14-27 combination showed apparent promoting ability on D.officinale when it was compared to the control.
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