| Teak(Tectona grandis) is the noblest wood in the world, enjoying the great reputation of “the king of woods” with super performance of fast-growing, high quality in timber, good processing and decorative characters, wide application range and high return on investment. The research and development of teak plantation have good social benefit, economic benefit and ecological benefit. In this study, genetic variation, genetic structure and genetic relationships were investigated on teak provenances and clones. Mean while, clone field trials were established at different provinces and sites. Seedling growth traits, gas exchange and chlorophyll fluorescence parameters of teak clones were measured and evaluated. Physiological estimate of cold stress on teak clones at seedling stage were also carried out. The teak clones of fast-growing and cold resistance were selceted through early evaluation as descripted above at phenotypic, physiological and molecular level. The successful implementation of this research has important scientific significance and application value. The main results were as follows:(1) The polymorphic information content(PIC) for each provenance ranged from 0.394 to 0.811, with a mean value 0.56. The unbiased gene diversity(Hz) were from 0.4692 to 0.8523 with a mean value 0.6612, showing high variation within teak provenances. The variation of India provenances > Burma provenances > Thailand provenances >Laos provenances.The He, Ho and NA of India provenances were 0.8056, 0.7114 and 10.2, repectively. Some of the early introduced provenances(Provenances 21, 26 and 24) were detected exist abundant variation and providing important implications in future plans for sustainable use of teak genetic resources.AMOVA analysis showed variance component 84.760% among individuals within provenances, 4.654% among provenances within countries, and remain 10.586% among four countries(P < 0.001). Plus trees from large teak population should be selected or conserved as more as possible in order to keep genetic variability for future improvement.A high gene flow Nm = 1.458 and moderate coefficient of genetic differentiation Fst = 0.146 indicated the gene flow among teak provenances was substantial and close neighbor breeding may occur in natural populations. The genetic distance matrix and UPGMA cluster showed relationships among different provenances. A Mantel test revealed a geographical pattern among native provenances(R = 0.7355, P < 0.001) proving geographic origin of introduced provenances have been identified as reliable in this study. The ten introduced provenances mostly from provenances 5, 6 or 7 or their adacent provenances.(2) A DNA-based fingerprint technique was developed for teak with 15 microsatellite markers, based on twenty-six widely cultivated teak clones. The 15 markers were used to investigate the genetic variations and relationships of the 26 teak clones. All the 26 teak clones could be unequivocally identified by the developed fingerprint technique. In terms of genetic diversity among 26 clones, a total of 160 alleles were detected with a mean of 10.67 alleles per locus. The observed heterozygosity(Ho) ranged from 0.3333 to 1.0000, averaging at 0.6567. Despite of the limited sample, there was a substantial genetic variation that could be exploited in teak breeding program. In addition, the UPGMA cluster analysis separated teak clones of India origin from Myanmar and essentially confirmed historically known or speculated origin of the clones. The origin of clones 108 and 3078-5 which selected from early planted provenances probably from India provenances, and 8301 may be from Myanmar materials which has been revealed by the dendrogram and genetic identity matrix.(3) The results showed that in Guangzhou august, there were abundant genetic variation in gas exchange, chlorophyll fluorescence and growth traits in teak clones. The clones 7029, 7122, 7559, 71-5 and 7219 have good growth performance at seedling stage. The genotypes 7029, 7219, 71-5, 7122 and 7412 had relatively high photosynthesis rate, and India provenances 3070, 3074 and 3071 could be considered as high photosynthesis rate. Photosynthesis rate had significant positive correlation with seedling growth. Photosynthesis rate(Pn), actual quantum yield of photosystem II centers(Yield), quantum efficiency of photosystem II centers(Fv/Fm) and stomatal conductance(Gs) were expected to be applicable for the evaluation of photosynthetic efficiency in teak resources.(4) It was showed that the curves of diurnal variations of net photosynthetic rate had one single peak curve in June at Guangzhou, the peak value 9.826μmol·m-2·s-1 was at 11:00, while it showed two-peak curves with “photosynthetic midday depression” in August and October, the highest peak values 8.317 and 11.915μmol·m-2·s-1 respectively were at 9:00, the second peak value was around 15:00 to 16:00 in August and at 13:00 in October. The average net photosynthetic rate of teak was October>June>August. Photosynthetic available radiation(PARo) is the most important ecological factor influencing the net photosynthetic rate of teak, and then is air temperature. PARo has great significant positive correlation with net photosynthetic rate, high temperature in June and August has great significant depressing effect to net photosynthetic rate.(5) The seedlings of different teak(Tectona grandis L. f.) clones were cultured at 6 degrees centigrade for 24 hours, and then 3 degrees centigrade for 24 hours, in order to estimate cold tolerance of different teak clones, the relative conductivity(EC), free proline(FPRO) content and superoxide dismutase(SOD) activity were measured for leaves of each tree before and after treatments. The result showed that the three physiological indexes had significant and highly significant difference among teak clones before and after treatments except SOD activity after treatment at 6 degrees centigrade for 24 hours. The relative conductivity and free proline content increased after chilling stress, SOD activity showed increased for some clones first increased and then decreased, while others inverse. Some teak clones became more cold resistant by increasing FPRO content and SOD activity. The teak clones 7559, 7531, Z408 and 7509 were screened as cold tolerance clones.(6) The tree height, DBH and individual volume of teak clones and clone×site interaction were significant difference at 3.5 years old. The variation coefficient of teak clones height at Dingan field trial was small(0.092), the variation coefficients of DBH at Hainan Dingan and both height and DBH at Yunnan Jinggu were larger(0.118-0.167), the variation coefficients of individual volume at Dingan and Jinggu were 0.327 and 0.305, respectively, showing good prospect in teak breeding. The heritability of height and DBH at Dingan field trial were 0.873 and 0.852, respectively. The heritability of height and DBH at Jinggu field trial were 0.851 and 0.773, respectively. The heritability of individual volume at Dingan and Jinggu were 0.863 and 0.0.784, respectively.Teak clones 7509, 7514, Z408, 7559 and 7029 were selected as fast-growing and cold tolerance based on growth of field trials, cold resistance investigation and physiological study. Teak clones of Burma provenances have higher cold tolerance than those from India provenance. In view of the different ecological area, the suitable clones of fast-growing for Hainan Dingan area are ranked as 3078-5, 7122, 7029, 7514 and 7559, and fast-growing clones for Yunnan Jinggu area are ranked as 7029, Z408, 7509, 7559 and 8301, the genetic gain of individual volume at Dingan and Jinggu reached 40.26% and 34.57%, respectively. The clones of fast-growing and cold tolerance for Guizhou Luodian area are 7514, 7509 and Z408, and clones of fast-growing and cold tolerance for Guangxi Bobai area are 7514, 7509, Z408, 7559 and 7029. |
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