| Eucalyptus plantations was one of main timber forests in China,A lot of studies have been devoted to improving eucalyptus timber yield,enhancing wood property and stress resistance to relief wood domestic demand.It was extremely urgent to breed strong wind resistance varieties for the eucalyptus plantations in coastal planting areas.Cross-breeding was one of the important means to improve the quantitative traits of eucalyptus.The F1 hybrids of E.urophylla×E.grandis from factorial mating system were studied using the open-pollinated progenies of\as controls.Multiple-year growth traits,10.3a wood traits and wind resistance trait of Eucalyptus urophylla×E.grandis F1 hybrids were investigated,their genetic parameters were estimated,correlation between growth traits,wood traits and wind resistance traits and superior hybrids and plus trees were screened by different breeding goals.It was aim to provide scientific basis for selection of eucalypt parents and application for their hybrid.The findings can provide reliable parent materials for a large number of artificial seed production and clones for eucalypt extension in the future.The main research conclusion were as follow:(1)ASReml-R software was applied to assess heritability,dominance effect,additive effect,parental effect and hybridizing abilities of growth traits when 1,2,4.5,8.3 and 10.3 years old.Mean single-tree volume was calculated for each hybrid combination,and superior combinations were determined as those with volume above mean+standard deviation of all combinations.Selection of plus trees conducted with two standards,I:mean+two times standards deviation,and II:mean+three times standards deviation.Growth performance of hybrids was obviously better than that of open-pollinated maternal off-springs at each age.Tree height,diameter at breast height(DBH)and individual volume at each age were significantly(p<0.05 or p<0.01)different among hybrid combinations,while no significant difference was observed among blocks.Maternal variance component of each growth trait was lower than paternal variance component when one or two years old,they were equivalent to each other when4.5 years old,while maternal variance component was higher than paternal variance component when 8.3 or 10.3 years old.As age increased,single-tree heritability(h~2)generally tended to vary from middle to low,family heritability(h~2F)from high to middle to low,while additive-to-dominance variance ratio(?_D~2/?_A~2)increased for tree height and DBH.Year-year and trait-trait genetic and phenotypic correlations were significant among hybrids.The general hybridizing abilities(GHA)of U21 and G8 were the highest among maternal and paternal parents,respectively,and the specific hybridizing ability(SHA)of U21×G5 was the highest among all cross combinations when 4.5 years old.When 8.3 years old,GHA of U21 and G19 were the highest,and SHA of U2×G19 was the highest.Maternal and dominance effect of each growth trait was lower than paternal and addtive effect when one or two years old,respectively,maternal and paternal effect were equivalent to each other when 4.5 years old,while maternal and dominance effect was higher than paternal and additive effect when 8.3 or 10.3 years old.A total of 7 superior cross combinations,one superior maternal parent and two paternal parents were screened out,and 40 and 16 elite individuals were determined according to Standards I and II,respectively.(2)Wood traits of Eucalyptus urophylla×E.grandis F1 hybrids were investigated,their genetic variation were studied and genetic parameters were estimated.ASReml-R software was applied to assess heritability,dominance effect,additive effect,parental effect and hybridizing abilities of wood basic density,fiber length,fiber width,the ratio of fiber lenth to width,cellulose,hemicellulose and lignin content.The family heritability(h~2F)and Single-tree heritability(h~2)of wood basic density was 0.514 and 0.051,respectively.The family heritability(h~2F)and single-tree heritability(h~2)of fiber length was 0.510 and 0.056,respectively.The family heritability(h~2F)and single-tree heritability(h~2)of fiber width was 0.788 and 0.187,respectively.The family heritability(h~2F)and single-tree heritability(h~2)of fiber width was 0.807 and 0.208,respectively.Single-tree heritability(h~2)generally tended to vary from middle to low,ranging from0.032?0.208,Family heritability(h~2F)from high to middle,ranging from 0.367?0.807.Maternal and addtive effect of wood traits was higher than paternal and dominance effect,respectively.FL showed positive rg with FW.However,trait-trait genetic correlatons among other wood traits were not significant.Trait-trait phenotypic correlations between BD and FW,BD and FL/FW,FL and FW,FL and FL/FW,HC and L were positive.Trait-trait phenotypic correlations between BD and L,FW and L,C and HC were negative.The maternal DU1 had a negative GHA in lignin and a positive value in other traits,and U2G19 had a negative SHA in lignin and a positive value in other traits.A total of 6 superior cross combinations,one superior maternal parents were screened out.(3)Wind resistance performance of hybrids was obviously better than that of open-pollinated maternal.Wind resistance value and stem exhibited significant differences among cross combinations(p<0.01),and showed not significant differences among blocks.Trait-trait genetic correlations between wind resistance value and growth traits were not significant.Trait-trait phenotypic correlations between wind resistance value and growth traits were significantly negative.Genetic correlations were significantly negative between wind resistance and FL,FW.Genetic correlations were not significant between wind resistance and remainder wood traits.Phenotypic correlations were significantly negative between wind resistance and FL,FW,FL/FW,and were significantly positive between wind resistance and HC,but were not significantly positive between wind resistance and BD,C,L.The hybridizing abilities of stem were estimated.The general hybridizing abilities(GHA)of DU1 and G9 were the highest among maternal and paternal parents,respectively,and the specific hybridizing ability(SHA)of DU1G19was the highest among all cross combinations.Hybrid combinations could be selected using independent culling and comprehensive index selection method to identify a production population that provide breeding material with inherently superior growth,wood properties,straight form and wind resistance required to develop high value products.A total of 3 and 7superior cross combinations were determined according to two method,respectively. |
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