Genetic Variation Of Wood Properties And Superior Clones Selection Of Ginkgo Biloba L.

Taking 139 Ginkgo biloba L. female clones from 9 provinces in China and Japan as test materials, this dissertation systematically studied their growth traits, wood anatomical structure, physical-mechanical properties, chemical properties as well as their law of genetic variation. On that basis, this study made a evaluation and selection on clones. The main conclusions were as follows:1. Trait variationAmong all the growth traits, except for the diameter and length of new shoots, there were very significantly differences among different clones.There were two kinds of wide and narrow tracheids with different shapes and structure in wood of Ginkgo biloba L. and the former was the main tracheid type. The cross-sectional shape of tracheid mutated greatly. The shape features indexes of the tracheid, including tracheid length, microfibril angle, double-wall thickness, lumen diameter, the ratio of cell wall to cavity, tangential diameter and radial diameter, were quite variable among the clones. And there were great variations of the shape and the arrangement modes of bordered pits among and within the clones.There were great variations of physical and mechanical properties of Ginkgo wood, such as wood density, shrinkage rate, and growth strain, among different clones and at different radial locations and heights. The maximum crushing strength differed significantly among different clones.There were significant differences of chemical properties, including the content of cold water, hot water, 1%NaOH, alcohol-benzene, lignin, cellulose, and of ash among clones. The corrosion resistance of wood differed greatly among clones. There were significant differences of the starting and final temperatures, as well as the rate of mass loss and thermal discharge at different thermal decomposition stages between different clones. And the surface activation energy differed greatly at different thermal decomposition stages between different clones,too.2. Genetic control of traitsThe repeatability of stem volume,diameter upon rootstock,length above rootstock,crown-width was over 0.70,and the repeatability of other growth traits were relatively low; The repeatability of the six tracheid feature indexes: tracheid microfibril angle, double-wall thickness,lumen diameter,ratio of cell wall to cavity,tangential diameter and radial diameter, were above the average. The repeatability of microfibril angle and tangential diameter were over 0.70; Among physical-mechanical properties indexes, the repeatability of air-dried shrinkage rate and basic density was over 0.60, except for the lower repeatability of Maximum crushing strength and surface longitudinal growth strains; The repeatability of chemical properties differs greatly, and repeatability of lignin,cellulose, ash and alcohol-benzene was much higher above 0.70 and was stable among the clones.3. Correlation of traitsCorrelations among the growth traits were relatively strong. The correlations among most indexes were positive with higher correlation coefficient, except for the correlation of the diameter of new shoots and the number of new shoot leaves being negative. Among the indexes of tracheid features, microfibril angle presented a positive correlation with Ratio of cell wall to cavity, and presented a negative correlation with double-wall thickness,diameter of cavity,radial diameter and tangential diameter. And except for the weak correlation with double-wall thickness, its correlation with other indexes reached a very significant level. The Correlation between lumen diameter, radial diameter and tangential diameter were also very strong.The 6 shrinkage indexes and the surface growth strain had a positive correlation at a significant level. The correlation between basic density and maximum crushing strength was also positive at a significant level. The analysis of principal components showed that the entire physical-mechanics indexes could be classified into two categories of indexes which reflected the shrinkage properties and mechanical properties of Ginkgo wood.The correlation coefficients of most chemical indexes were not significant. the correlation among different extracts,the correlation between the content of cellulose and lignin,the correlation between the content of cellulose and the corrosion resistance, and the correlation between the content of lignin and the indexes of thermal decomposition were relative strong.This study also analyzed the correlation of growth traits, wood anatomy and chemical properties with physical-mechanical properties. The conclusions showed that: Growth indexes and dried-air shrinkage indexes had a negative correlation, and it had a weak correlation with other physical-mechanical indexes; microfibril angle presented a negative correlation with shrinkage rate, a significant positive correlation with basic density,and a weak negative correlation with Maximum crushing strength and surface growth strains; Radial diameter and tangential diameter of tracheids presented a positive correlation with shrinkage rate, a negative correlation with basic density, and a weak negative correlation with Maximum crushing strength; There were a weak correlation between chemical properties and physical-mechanical properties, which principally presented as follows: there were significant positive correlation between cold water extracts and basic density as well as maximum crushing strength. There were a significant negative correlation between alcohol-benzene extracts and tangential shrinkage rate as well as surface growth strain. There were a positive correlation between lignin and cellulose as well as Maximum crushing strength, and a very significant negative correlation with surface growth strains.4. Selections of clonesAccording to the analysis results of genetic parameters and correlations of different indexes, within the four index systems of growth, anatomy, physical mechanics, and chemistry, we selected superior clones with high growth, good anatomical structures, stable physical-mechanics features, and proper chemical components in different test fields. According to the correlation and the repeatability, from 4 categories of indexes, this study chose 5 indexes, which were diameter upon rootstock,tangential diameter, dried-air shrinkage rate of volume, basic density and lignin content, as the comprehensive indexes to select clones, and established a index selection mathematical equation : I=0.1171x1-0.3749x2+12.0533x3-0.7948x4+0.7120x5The rate of accuracy of comprehensive selective index rH I=0.9982,index hereditary captivity h I2=0.9225,Progress in integrated breeding selectionâ–³H =2.594. This study selected 16 clones in Sun Chukou of Tan cheng with the largest selecting index 005# . its comprehensive indexes of growth, anatomy, physical-mechanics, and chemical components were superior to other clones. This showed that this system of selection index could reflect the basic traits of Ginkgo wood comprehensively.This dissertation also made a discussion about systematic evolution, correlation among indexes, genetic control and clone selection of Ginkgo biloba L.