Selection And Breeding Of E.urophylla Clones

Nowadays Eucalyptus urophylla S.T.Blake has become the main Species of Eucalyptus plantation in southern China for its rapid growth, far-ranging adaptability and multiple use characters. Its superior clonal forest showed merits of high selection efficiency, rapid genetic gain, high yield, sizable forest tree, easy to management and good economy. With the unceasing advance of intensity of plantation management, specially increasing demands of raw materials of pulp and paper and wood machining industry demand and continual development of large scale short-rotation industry raw material forestry. Breeders were exigent requested for emphasizing on tree genetic improvement, special clonal breeding. In this thesis, E.urophylla clones became the research object and the characters genetic variation, multiple characters selection, seedling photosynthesis, correlation analysis of growth characters between early and late period were undertaken. Meanwhile, E.urophylla clone short-term selection program and long-term breeding strategy also proposed and discussed. The main results were as follows. There highly significant differences in growth, form quality and wood quality characters among clones. Totally 73 clones their individual tree volume (Vol) were bigger than total clones average from Expt.97C01, Expt.01C01 and Expt.02C01. The clone with best growth performance its 4-year-old average values of Vol, height (H) and diameter of breast height (DBH) reach 0.2396m~3,19.34m, 19.28cm and 102.36%, 21.33%, 31.42% higher than the total average of its clone population, respectively. All characters showed middle to strong genetic coherence. There are close positive correlations relationship among growth characters except ratio of height and DBH. Wood base density (BD) and bark proportion showed close negative correlations relationship. BD and stem form (SF) exhibited certain independence, Each multi-characters selection methods have its advantages and disadvantages. In general, multi-characters select index could select compositive characters clones and become the better method for evaluating E.urophylla clones which play good performance in growth, form quality and wood quality characters. Three equations of Expt.97C01, Expt.01C01 and Expt.02C01 were established by using select index method of multi-characters. At the same time, Respectively, 6, 3 and 18 superior clones were selected with 14.286%,25.0% and 19.355% selection rate by using the criterion which large than the total select index average and plus a select index standard deviation. E.urophylla clones showed high net photosynthetic rate (Pn) and transpiration rate (E). All photosynthesis were significant differences between clones. The net photosynthetic rate (Pn) of E.urophylla and irradiance had a conic correlation evidently, the light response saturation point was 1967.7μmolm-2s-1. It was resemble that of daily variation of Pn, E and leaf conductance (Cond) with sizable measure data at 8:00am-16:00pm and fall down to the lowest point at 18:00am, but leaves of intercellular CO2 concentration (Ci) and Pn showed the other way round in the diurnal courses. Mostly photosynthesis characters have definite correlation with field growth characters. The results could be useful for early selection of superior E.urophylla clones. After 3.5 years old, phenotype and genotype correlation coefficient of growth characters of E.urophylla clone were significant differences between early and late period. Five mathematic models were established and results of regress equation with characters include Dearly—Dlate, Vearly—Vlate and Dearly—Vlate would be more reliable. Base on comparison of year efficiency and the best select age of different growth characters, the early selection effects in 1/2 to 2/3 ages of E.urophylla clone plantation rotation may as well. The short-term selection of E.urophylla clone aim at application purpose and run into operation phase via create clones by different methods, testing in adaptive areas and integrated evaluation. The long-term breeding strategy should be emphases on sustainable breeding program. The author suggest that breeders should focus on supplement and introduction, adopting inter-developmental strategy between sexual reproduction and clone utilization, developing high and new technique to Promoting the course of E.urophylla clone breeding, undertaking research of combinatorial technique with high efficiency and establishing new manage system.