| Constructing seed orchard is a kind of breeding method for high yield and quality.We can get more and better germplasm resources through the evaluation and selection of the mother trees and their offspring in the seed garden.which speed up the improvement process,shorten the breeding cycle and provide the basis for the reconstruction of seed orchard.This study is conducted on 47 seed trees in seed orchard,evaluating them through measuring their flowering phenology,seed yield,growth,wood properties and several other traits and growth traits of their clones and offspring.The main results including:The result of the determination of flowering phenology,seed yield,germination,DBH increment,stem form and wood properties of seed trees in the seed orchard showed that:The trait,florescence of seed trees in seed orchard were concurrent between April and May in two consecutive years.The seed orchard was found to have biennial bearing by 4 consecutive years.There are 10 trees had flowers and seeds in 4 consecutive years.3-16 mother tree with a seed yield of 919g in four years was the highest,and the seed vigor of 3-40 mother tree is also the highest among them.The diameter growth of seed trees on average were more than 1.0cm.There are 4 plants with straight stem,3-3,3-4,3-24 and 3-28,grew more than 2.0cm.Eight trees whose wood density,fibre length to width ratio.hemicellulose and holocellulose were 4.99%?8.67%?3.30%and 1.12%higher than the mean were evaluated as excellent ones.35 clones have been vegetative propagated from 47 seed trees.The results of ANOVA showed that there were significant differences(P<0.01)in their height,ground diameter,distance and branch numbers.By the evaluation of membership function,9 clones were rated as excellent clone,whose seedling height,ground diameter,distance and branch number were 7.54%,10.31%,5.71%and 6.25%higher than the average value of population.The growth curve of seedling height was fitted by Logistic equation,The duration and height growth of the study found that the longer the duration of growth was greater.the fast-growing duration is more than 80 days of 6 clones is the maximum.The growth traits,seedling height and diameter of half-sib families in seed orchard,were evaluated in 2014 and 2015.The results showed that the level of various characters in the family was under highly genetic control and the heritabilities were above 0.8,indicating that the selection of progeny was reliable.Seven excellent families,whose genetic gain of seedling height and ground diameter was 25.10%and 0.15%were selected from 21 half-sibs in 2014 using breeding value.Similarly,genetic gain of seedling height and ground diameter of four excellent families was 21.98%and 0.17%were selected from 18 half-sibs in 2015.Forty-seven seed trees were used to investigate the effect of GA4+7 and GA3 on flowering of Betula platyphylla.The results showed that gibberellin(GA4+7,GA3)had effect on blooming and seeding of Betula platyphylla.The effect of the first batch was the most significant.The male inflorescence,female inflorescence and seed yield of the parent tree treated with GA4+7 were 78.84 times,3.90 times and 3.40 times of CK,respectively.The male inflorescence,female inflorescence and seed yield of the parent tree treated with GA3 were 32.38 times,7.39 times and 9.97 times of CK,respectively. |
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