| Populus tomentosa Carr. is an excellent sort of tree used in afforesting and industrial lumber in China. In order to improving the wood quantity and quality of Populus tomentosa, it is necessary to carry out the molecular regulation and genetic improvement in wood property. In this research, the major results are described as follows:(1) Sucrose synthase (SS) catalyzes the decomposition of Sucrose to UDP-glucose (UDPG), which is the precursor for cellulose formation in plants so as to relate to wood formation. The research of the SS gene in Populus tomentosa has the important theoretical significance for analysing the functional mechanism of gene family, and will provide insight into the study in other perennial woody plants.3 full-length cDNA clones encoding PtSS gene family were isolated from the cDNA prepared from stem of Populus tomentosa by the RT-PCR method. The PtSS1.1, PtSS2.1, and PtSS3.1 are 2,418 bp,2,412 bp, and 2,475 bp in full length, respectively, which encoded protein of 805,803, and 824 amino acides, respectively. The three members share the two characteristic functional domains:a sucrose synthase domain and a glucosyl-transferase domain. The deduced protein sequence of the PtSS1.1, PtSS2.1, and PtSS3.1 all shared 99% highly identity with PtrSS1.1, PtrSS2.1, and PtrSS3.1, respectively. Tissue expression profile indicated that all 3 genes were expressed in each tissue and were abundant in root and vegetative bud. For drought stress, genes PtSS2.1 and PtSS3.1 presented a sharp rise before down regulation, while PtSS1.1 presented the relatively stable expression. Transgenic poplar with the over-expression vector were generated via Agrobacterium tumefaciens-mediated leaf disk transformation methords and obtained 14 positive transgenic ramets for further research.(2) The growth traits and wood physical and chemical component largely determine the wood properties. In this study,3 new hybrid white poplar clones and P. tomentosa ’LM50’ were selected to investigate clonal variation in growth traits and wood properties. The growth traits of four 7-year-old clones were examined at three sites (Fengfeng nursery, Guanxian nursery, and Weixian nursery). We also measured the wood properties of four 6-year-old clones at the Fengfeng nursery. Results of ANOVA analysis were as follows:1. growth site significantly impacted variation in growth traits. The growth of 7-year-old clones was fastest at the nursery in Fengfeng and slowest at the nursery in Guanxian.2. The stem volume ranking of the hybrid clones differed among sites. Yiyang-1 differed significantly from LM50 and Yiyang-3 in Fengfeng nursery, and not differed significanthy from Yiyang-2. Yiyang-1 differed significantly from Yiyang-2 and Yiyang-3 in Weixian nursery, and not differed significantly from LM50. For all the three sites, Yiyang-1 was ranked first in average growth, followed by Yiyang-2, LM50, and Yiyang-3.3. Fiber traits and chemical components were distinctly different among the clones, the fiber of Yiyang-1 was long and thin, with the higest length-width ratio (44.83), the content of holocellulose (77.35%). and the lowest content of lignin (19.72%). With regard to the comprehensive growth rate and wood fiber traits, Yiyang-1 exhibited the best performance among the four hybrid poplar clones, followed by LM50, Yiyang-2, and Yiyang-3. |
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