| Eucalyptus urophylla is one of the most important species in improvement programs of eucalypt in China.A large amount of germplasm resources rich in genetic diversity have been accumulated for a long time.Now,the improvement in E.urophylla was in the 3rd generation.The genetic materials in 2nd generation breeding population were composed of plus open pollination progenies from 1st generation breeding population by a high intensity of artificial selection.The genetic materials in 3rd generation population comprised the plus open pollination progenies from 1st and 2nd generation breeding populations,also through a high intensity of artificial selection.So,significant changes of the genetic diversity and genetic structure have taken place,and the relationship of genetic material have an inheritance among three generation breeding population.In this scenario,before pushing the improvement program of E.urophylla into the advanced one and the selection of genetic materials composed the advanced generation,the analysis for the genetic diversity and structure of three generation breeding population existed is needed.The current study aim to:(1)evaluate the genetic diversity and genetic structure of three generation breeding populations by microsatellite locus,this analysis include to character the level of genetic diversity and genetic structure of natural provenance in 1st generation,and to compare the characteristics changed of genetic diversity and genetic structure among three generation breeding population of E.urophylla;(2)assess the genetic variation of interested traits of three generation breeding populations.Exploring the practicability of fast prediction for interested traits using near infrared spectroscopy(NIRs)in eucalypt;(3)Search the microsatellite loci associated with wood density and growth traits by association analysis in E.urophylla.The main results in this study were as following:(1)The test of Hardy-Weinberg equilibrium in three generation breeding population by microsatellite loci all showed a genetic disequilibrium.Meanwhile,the test of Hardy-Weinberg equilibrium also demonstrated a strong heterozygote deficit in three generation.(2)459,313,and 428 alleles were detected by 16 microsatellite loci in three generation breeding populations respectively.Shannon's information index(1.966,2.093,and 2.265)indicated that the level of genetic diversity was consistent among three generation.The statistics of polymorphyism information content(0.859,0.840,and 0.866)showed three generation population possessed a high polylimorphysm.A high level of genetic diversity was proposed by the values of expected heterozygosity(0.807,0.830,and 0.857).(3)The overall mean of genetic distance were 0.450,0.238,and 0.249 respectively,of genetic identity were 0.645,0.788,and 0.781 respectively,of genetic differentiation were 0.044,0.021,and 0.018 respectively,of gene immigrants were 6.387,11.506,and 14.393 respectively in three generation breeding population of E.urophylla.All these statistics demonstrated a decline of genetic differentiation,and an increasing in gene migrants among natural provenances and subpopulations generation by generation.(4)AMOVA results demonstrated that most of the genetic variances(near 70%)were explained within individuals,a little more than 30% of total genetic variance occurred among individuals within population,and among populations accounted for the least molecular variance.The subpopulations were classified by Structure analysis was well coincided with the cluster analysis by UPGMA method based on genetic distance of individual.The number of subpopulation classified by Structure analysis was 4,this was not consistent with the geographic distribution of natural provenances.(5)The genetic variation of wood density and growth traits by ANOVA suggested that significant difference(at significance level of 0.05)were found among natural provenances and subpopulations in three generation breeding population of E.urophylla.The clusters analysis by Multiple Comparisons(LSD)based on mean difference in wood density,diameter at breast height,and tree height indicated that the significant of phenotypic differentiation wasn't too high based on mean wood density,a relative high significant phenotypic differentiation was find based on growth traits among natural provenances and subpopulations in three generation breeding population of E.urophylla(at significance level of 0.05).(6)The NIRs calibrated model of wood density,fiber length,and fiber width were created by the method of partial least squares(PLS).The determination coefficient(R2)between measurement and prediction of three models were 0.93,0.94,and 0.92 respectively,and root mean square error of calibration(RMSEC)between measurement and prediction of three models were 0.007,0.013 and 0.254 respectively.The efficiency of three NIRs model tested by independent validation set all demonstrated a well prediction.(7)The overall mean of explained phenotypic variation of loci associated with wood density,diameter at breast height,and tree height were 43.8%,67.6%,and 40.1% respectively in population T164,the overall mean of explained phenotypic variation of loci associated with same three traits were 24.3%,40.5% and 55.4% in population T77.The values of explained phenotypic variation indicated the loci detected had a strong genetic control for interested traits.(8)There was no one locus associated with same trait in two populations.Relative more loci associated with wood density were detected in two populations,more less loci associated with growth traits.In population T164,locus EUceSSR900 associated with wood density and tree height simultaneously,locus EUceSSR425 associated with wood density and diameter at breast height once.Locus EUceSSR900 was detected by GLM model and MLM,it implied the possibility of false positive was eliminated greatly.The locus Embra100 associated with wood density at extremely significant level(P<0.001),the explained phenotypic variation of Embra100 was 75.8%,it was much higher than average value of loci associated with wood density.The number of loci associated with wood density and that with diameter at breast height was close in population T77. |
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