Study On The Secure Conservation Of Oryza Officinalis Wall In Guangxi

O. officinalis in Guangxi is the very important germ plasm resource in our country. It is given priority to in-situ conservation at present. Because the popularizing of the new variety of cultivated rice tends to simplify in its genic background, and the demonstration of the transgenic rice in the areas where the wild rice exists, may be dangerous to the genetic diversity of the wild resource. Conservation biology has to resolve whether the local wild resource is imfluenced by the gene flow from the cultivated rice, and whether the transferred gene of the transgenic rice will flow to the wild rice .In order to determine the conservation strategy of O. officinalis, this research was divided into 2 parts.Part 1 was genetic diversity analysis. In order to estimate the genetic diversity and the genetic structure of O. officinalis, a total of 261 individuals from 10 O. officinalis populations from different areas in Guangxi were analyzed with 21microsatellites loci. Part 2 was the cytological study, The gennination and growth of O. officinalis pollen grains on the stigmas of the same cultivated rice were observed with optical-microscope, and the results were compared with those of cultivated rice and O. rufipogon at the corresponding time. This method helped us to estimate the cross- compatibility between cultivated rice and O. officinalis straightly and simply, and to conclude whether transgenic rice would influence the genetic diversity through gene flow. The result was the following :First, The genetic diversity of O. officinalis in this study was moderately abundant. The mean number of alleles (A) was 1.78. The effective number of alleles (Ae) equaled 1.37. The observed heterozygosity (Ho) was 0.14. The mean expected heterozygosity (He) equaled 0.22, and the percent of polymorphic loci was 80.65%. The result showed the level of O. officinalis in Guangxi was higher than the mean level of O. officinalis in the whole country, which was described by Gao Li-zhi. F-statistic showed that about 50% genetic variation existed among the populations of O.officinalis and 50% existed within the populations (Fst=0.50). Most populations deviated from Hardy-Weinbergexpectation and slight deficiency of heterozygotes was observed (Fis=0.27, Fit-0A9). The dendrogram of accessions of 10 populations showed that the geographic distance of the populations did not show positive correlation with the genetic diversity, and the presence of cultivated rice had influences on the genetic diversity of O. officinalis. Six populations around with rice paddy were clustered together, although they had different geographic distances. Population 10 lied in the bottom of a reservoir without any paddy field around, led to a very low genetic diversity. Based on the geographic information, water system was also important to decide the genetic distance of certain populations. The result showed that being near to the cultivated rice could chang the genetic construction of the wild rice as well as the water system.Second, The pollens of the cultivated rice grew fast in the cultivated stigma. A great lot of pollen tubes germinated only 2 min after pollination., and the pollen tubes reached the style 30 min later. The germination and growth of O. rufipogon pollen grains on cultivated rice stigma were normal and quick, which was similar to those of cultivated rice. The pollen grains of O. officinalis also could germinate after pollination. It was observed that fewer numbers of pollen grains adhered to the stigmas. The time when germination started after cross was delayed. Fewer numbers of pollen grains germinated. Some pollen tubes failed to enter into the stigmas, they just twined or circled on the surfaces of the stigmas after germination. Some pollen tubes could enter into the stigmas and grew slowly, and some pollen tubes were observed entering into the style straightly through the style. The results indicated that there was better procreation isolation between cultivated rice and O. officinalis, and the potential gene flow between transgenic rice and O. officinalis was low, but the possibility of gene flow could not be excluded.From above conclutions, meatures were advanced on the conservation of the O. officinalis. Because O. officinalis Wall populations are usually small in nature, and the mating type gives priority to autogamous style, the genetic variation mostly existed among the O. officinalis populations. More populations of O. officinalis and fewer individuals within populations should be sampled for ex situ conservations. Populations with lesser samples still had abundant genetic variation, small populations of O.4officinalis should be considered when conservation strategy is made. Meanwhile, though the sexual compatibility between transgenic rice and Oryza officinalis was low, the potential gene flow from transgenic rice still had non-neglectable effect. The transferred gene of transgenic rice had potential dangers to the genetic diversity of O. officinalis. Therefore, suitable distance should be designed between the habitats of O. officinalis and transgenic rice fields. Meanwhile, ex-situ conservation bondig the biology technology methods will also be considered to conserve the resource of O. officinalis in maximum.