| This study is on genetic diversity and population structure of Oryza rufipogon near the tropic of cancer in china, and gene mapping of multi-ovary in rice.1. The tropic of cancer in china has been recognized to be a center of wild rice with abundant superior genes such as resistance to diseases and pests. To provide information for the conservation of Oryza rufipogon in this area, 342 individuals from 13 populations near the Tropic of Cancer were collected and studied on the genetic diversity and population structure with 26 pairs of SSR primers which were distributed among the genome of rice. The results indicated that: (ⅰ) A moderate to high level of genetic variation both at species (Al=9.154, Ae=4.446, I=1.547, He=0.671) and at population levels (P=95％, Al=4.219, Ae=2.394, I=0.905, He=0.476). (ⅱ) The genetic differentiation among populations (Gst=0.30) suggested that 30％genetic variation existed among populations. (ⅲ) The results of cluster analysis and principle coordinates analysis (PCO) showed that genetic identity among populations was negatively correlated with geographical distance, as expected under the isolation by distance model. Together with the pattern of genetic diversity and structure of 13 the nature populations, population G 13 and G06 should be given priority to be conserved in-situ.2. The development of flower organ has well been studied to deeply understand the genetic mechanisms of flowering. In this study, a Chinese landrace named "compound rice" with unusual numbers of pistils and stamens was selected to study the mechanism of multi-ovary related gene. Through investigations of multi-ovary numbers of "compound rice" and its progenies with normal rice varieties and the analysis on gene mapping with molecular markers, some results were obtained: (ⅰ) The total of 100 flowers was randomly selected and examined. The numbers of stamens were generally from 6 to 8, and flowers with 7 and 8 stamens were frequently observed, each accounting for 40％. The numbers of pistils varied from 2 to 8, but more than 80％of the observed flowers had 2 or 3 pistils. The numbers of other floral organs are generally normal. Taking into the seed setting, two or three seeds were often observed in a single floret. (ⅱ) Crosses between the "compound rice" and the normal varieties of Aijiaonante and Nanjing 11. All flowers of F1 plants exhibited wild-type phenotype with normal numbers of stamens and pistils. However, F2 populations segregated with different numbers of stamens and pistils. In this study, we mainly focused on the number of ovary. The segregation rates of single ovary and multi-ovary plants are approximately 3:1 in F2 populations based onχ2text, indicating that the mutant characteristics are controlled by one recessive gene, temporarily namedfon(x). (ⅲ) With BSA-RCA strategy and SSR markers, fon(x) was mapped on the chromosome 11 between RM21 and RM27058, with the genetic distance of 0.05cM and 0.10cM respectively. The SSR marker RM27051 is co-segregated with the fon(x) phenotype in the two F2 populations from the wild type×the "compound rice". Because fon(x) shows phenotype and molecular mapping similar to fon4 (fon2), it might be different allele in thefon4 (fon2) locus or the same gene with fon4 (fon2). To confirm the conclusion, it is necessary to test whether these two genes are allelic with each other afterwards. |
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