Genetic Variation Of Wood Properties And Comprehensive Selection For Superior Clones On Populus Ussuriensis Kom

In order to explore the genetic variation of the Populus ussuriensis Kom,provide fast-growing high-quality varieties for the northeast forest areas and provide resistant clones for difficult sites such as barren hills and wastelands,based on the 9-year-old 45 P.ussuriensis clones in the Maoershan Experimental Forest Farm of Northeast Forestry University and the 8-year-old 20.ussuriensis clones in Qing'an Forest Farm,the genetic variation analysis,variance analysis,related analysis of growth traits(tree height,diameter at breast height,volume)and wood properties(basic wood density,fiber length,fiber length-width ratio,microfibril angle,cell wall percentage,fiber double wall thickness,vessel proportion,wood fiber proportion,wood ray proportion,cellulose content,hemicellulose content,holocellulose content)and superior clones selection were carried out and polyethylene glycol(peg-6000)was used to simulate drought to study the tolerance of the superior clones of P.ussuriensis.The main research results are as follows:1.There were significant differences in tree height,diameter at breast height and volume,and the phenotypic variation coefficient was 15.23%-54.28%.There were significant differences in basic density,fiber length-width ratio,fiber double wall thickness,vessel proportion,wood fiber proportion and holocellulose content among the clones,with phenotypic variation coefficient was 3.27%-20.46%.The heritability of growth traits was 0.714-0.860,and the height,diameter at breast height and volume were controlled by intensity heredity.The heritability of wood properties was 0.220-0.749,and most of the wood properties were controlled by medium to strong heredity.2.The basic density was positively correlated with fiber length-width ratio and negatively correlated with fiber length.Fiber length was positively correlated with fiber double wall thickness and wood ray proportion.The fiber length-width ratio was positively correlated with cell wall percentage,fiber double wall thickness and wood ray proportion.Fiber length was positively correlated with growth traits,while basic density,fiber length-width ratio and growth traits were negatively correlated.3.The superior clones of.ussuriensis were selected at the selected ratio of 15%.The clone D16 were selected at two test sites and could be planted as fast-growing clone in Xiaoxing'an Ling area and Zhangguangcai Ling area.The clones with excellent growth traits and wood properties at the Maoershan test site were C16,J19,H13,B6 and 18.The genetic gain of volume was 27.42%.The genetic gain of fiber length,fiber length-width ratio,fiber double wall thickness,wood fiber proportion was 0.94%,1.38%,5.17%and 1.02%,respectively.The Qingan test sites were C1,D16 and D13.The genetic gain of volume was 19.63%.The genetic gain of basic wood density,fiber length,holocellulose content was 0.28%,0.90%and 0.24%,respectively.4.Drought stress inhibited seedling height,ground diameter growth and biomass accumulation of seedlings and increased with stress intensity.The leaf membrane was seriously damaged,the relative water content decreased and the relative electrical conductivity increased.The contents of proline,soluble protein and soluble sugar increased first and then decreased,and the change range of mild stress was smaller than that of moderate stress and severe stress.Both at the early and middle stage of stress were higher than the control,indicating that the seedlings had certain drought resistance.At the end of stress,the seedling cells and tissues suffered irreversible damage.P.ussuriensis can endure mild drought stress environment in a short period of time.Moderate and severe drought stress have significant influence on the growth and physiological process of P.ussuriensis seedling.