Genetic Dynamics And Mating System Of Oryza Rufipogon Griff

Oryza rufipogon Griff.known as the ancestor of Asian cultivated rice(O.sativa L.),is the most important germplasm for rice improvement.It has made great contributions to improvements in rice yields.For example,from O.rufipogon,the gene tolerant to abiotic stress in Xiniuwei of Guangdong Province,the male sterility gene in Sanya county of Hainan Province,QTLyldl.1 and yld2.1 genes in Malaysian are utilized successfully in increasing rice yields.Unfortunately,the wild rice is now under seriously endangered status.To better understand genetic dynamics and mating systems can be particularly informative to obtain a conservation perspective of the species for further in situ conservation and germplasm management.By using SSR methods,the present study was conducted to compare the genetic variability between in-situ and ex-situ conserved O.rufipogon populations,between in-situ conserved and not conserved O.rufipogon populations,between maternal and progeny;to estimate mating system of natural O.rufipogon populations;and to analysis the genetic dynamic between maternal and progeny populations of O.rufipogon.The main results were as the follows.1.Comparisons of genetic variability between the in-situ and ex-situ conserved O.rufipogon populations in Jiangyong county of Hunan Province.Comparisons of genetic diversity levels of Jiangyong O.rufipogon were performed between the ex-situ and in-situ conservation populations by using 48 polymorphic SSR markers.A total of 166 and 119 alleles were scored in the ex-situ(G3) and in-situ(G4) populations,with the average of 3.55 and 2.60 per marker,respectively.The percentage of polymorphic loci(P),the mean number of observed alleles(A),the mean effective number of alleles(Ae),and gene diversity(He) in population G3 and G4,were 99.4%vs.95.2%,1.99 vs.1.95,1.428 vs.0.508,0.272 vs.0.304,respectively.It was indicated that relatively richer genetic variability existed in the population G4,although some unique variants existed in the population G3.For the in-situ population G4,43.4%of total variation existed between subpopulations(Gst=0.434),suggesting genetic variations were mainly held within subpopulations,and the genetic diversity levels between the four subpopulations showed the order from higher to lower were G4-1＞G4-3＞G4-4＞G4-2.2.Comparative studies on the genetic variations between Conserved and non-conserved Oryza rufipogon populationsEstimations of the levels of genetic diversity of the in-situ conserved populations of Oryza rufipogon in comparisons with the populations without conservations were conducted by using 24 SSR loci.The samples included 356 individuals from 5 conserved populations located in Dongxiang county,Jiangxi province(JXD),Chaling county and Jiangyong county,Hunan province(HNC and HNJ),Gaozhou city, Guangdong province(GDD),and Danzhou city,Hainan Province (HN),and 3 non-conserved populations in Wuxuan county and Laibin city,Guanxi(GXW and GXL) Automonous Region and Gaozhou city, Guandong Province(GDP).All the 24 loci were polymorphic in this study,among which,18 loci exhibited heterozygosity deficit.The highest observed heterozygosity (Ho) was generated by RM339,while the highest expected heterozygosity(He) appeared at RM336.In General,all these wild populations showed a high level of genetic diversity.Among the 5 conserved populations,the mean effective number of alleles(Ae) ranged from 1.780(JXD) to 2.504(HNJ),He ranged from 0.397(JXD) to 0.555(HNJ);For the 3 populations without conservations,Ae varied from 2.153(GDP) to 3.226(GXL),He from 0.492(GDP) to 0.640(GXL), respectively.Nei's genetic distance was 0.6585 between 5 Conserved populations and 3 non-conserved populations.It demonstrated that the populations without conservations had great value of Conservation and collection in spite of some populations conserved.The evaluation of genetic differentiation showed that 39.9%SSR variation was distributed among populations(Fst=0.399).F-statistics showed that these populations presented a slight deviation from the Hardy-Weinberg equilibrium(Fis = 0.147).The population GDD,GDP,HND showed slight heterozygosity excesses with Fis ranged from -0.03(GDP) to-0.186(HND).The population JXD showed slight heterozygosity deficits with Fis= 0.109,and the population HNC,HNJ, GXW and GXL showed significant heterozygote deficits in tests of Hardy-Weinberg equilibrium and significantly positive Fis values ranged from 0.315(GXW) to 0.473(HNJ),such pattern might be related to the relatively higher inbreeding in these wild populations.3.SSR analysis for mating system and genetic dynamics in O.rufipogon populations.To understand the mating system of O.rufipogon and the population dynamics,2353 progenies from 150 open-pollinated families sampled from 267 maternal parents of 6 populations from Jiangxi Province (JXD),Guangdong Province(GDD and GDP),Guangxi Province (GXW),and Hunan Province(HNJ and HNC) were analyzed by the SSR assays using 14 SSR loci.Genetic diversity of maternal and progeny populations were compared and the multilocus population outcrossing rate(tm),the single-locus population outcrossing rate(ts) and the single-locus inbreeding coefficient of maternal parents(F) were estimated for each progeny population.3.1 SSR analysis for genetic dynamics between maternal and progeny in O.rufipogon populations.Results indicated that genetic diversity of progeny populations may be estimated using 3 times random sampling from total progeny materials after grouping by families,then compute an average of statistical results of 3 times random sampling.The levels of genetic diversity varied among the sampled progeny populations,with Ae ranged from 1.7193 to 2.7781,NeisHe ranged from 0.3218 to 0.5891.The LSR-test results of genetic diversity varied among different Parameter values showing genetic diversity.Mean Fst=0.4181 indicated that there was a significant genetic population differentiation and about 41%of the total genetic variation existed among the progeny populations.The average of the overall FI for 3 times random sampling from total progeny populations was 0.4635,with FI ranged from 0.4537 to 0.4767 and each progeny population had a positive FI value, suggesting significant heterozygosity deficits and a significant deviation from Hardy-Weinberg equilibrium.There was gene flow(Nm) between progeny populations.The average of Nm for 3 times random sampling from total progeny populations was 0.3479,with Nm ranged from 0.3443 to 0.3518.The Ho of sampled progeny population was lower than that of sampled maternal population,while the FI of sampled progeny population was higher than that of sampled maternal population,which suggested heterozygosities in sampled progeny population was lower than that in sampled maternal population for every one.The ratio of Neis genetic diversity between progeny and maternal population pairs ranged from 0.9431 in population HNJ to 1.1412 in population GDD.There was not significant difference of gene flow(Nm) between progeny populations compared with that between maternal populations(0.3479 vs. 0.3424),and Fst values showed a similar pattern(0.4196 vs.0.4181). Within each sampled progeny and maternal population pairs,the similarity coefficient was more than 0.98.These results:indicated the progeny population represented more than 98%variability of its maternal population.3.2 Analysis for mating system parameters for 6 natural populations of Orzya rufipogon.O.rufipogon possess a mixed type of mating system,although outcrossing rate was variable among populations.The multilocus outcrossing rate(tm) ranged from 15.1%(HNJ) to 41.8%(GXW),and the single-locus outcrossing rate(ts) ranged from 10.1%(HNJ) to 28.5% (JXD).There was Inbreeding because there was significant difference between tm and ts.The correlation of paternity(rp) for the multilocus ranged from 0.607(HNJ) to 0.718(GDP) Which indicated a higher fraction of Siblings shared the same father.The population GDD,GDP exhibited heterozygosity excess,while population JXD,GXW,HNJ and HNC had significant heterozygosity deficit.The correlation of paternity for the multil~cus significantly differed from the correlation of paternity for the single-locus,with rp(s)-rp(m) ranged from 0.807 in population HNJ to 0.918 in population GDP,which suggested there are substructure for every sampled population.3.3 Implications of the results to ex-situ conservation and in.situ conservation.The paper put forward suggestions for in-situ conservation and ex-situ conservation of O.rufipogon in Jianyong,Hunan.The results supported that collection and conservation seeds of progeny population of O.rufipogon can not be neglected.The present study recommended the strategy for conservation of O.rufipogon that a single panicle can be as a unit to ex-situ seed-producing,collecting and conserving.Meanwhile the possibilities of inbreeding depreesion and the necessity of monitoring genetic dynamics of in-situ conservation population were assessed.Some improving measures for further in-situ and ex-situ conservation of O. rufipogon also discussed.