杉木第4代育种候选群体的12年生全同胞子代测定表现与选择

【目的】福建-南京林业大学合作的杉木多世代遗传改良计划,于2006年起陆续开展第4代育种候选群体的遗传资源创制、测定和评价。本研究旨在通过全同胞子代测定(第4代育种候选群体系列测定之一),为2016年启动的杉木第4代种子园营建技术研究和后续的生产性种子园建设提供优良亲本。【方法】 分别测定了杉木第4代候选群体中第2批1个12年生全同胞家系测定林1~12 a树高,4、5、 6、9和12 a的胸径,计算参试家系的单株平均材积;选取所有小区家系内的12年生的最优单株,采集胸高木芯样品测定木材基本密度和红心材比例。根据参试家系生长性状年度均值和变异系数评价家系生长性状稳定性;在方差分析基础上,估算遗传方差和遗传力;比较不同林龄、不同选择率以及早期选择对12年生时入选家系的准确率和材积遗传增益的影响。最后,以材积遗传增益为主要指标,兼顾材性性状,开展优良全同胞家系和家系内优良单株选择,预测入选家系和单株的遗传增益。【结果】 杉木第4代候选群体第2批62个全同胞子代测定结果表明,参试家系12 a平均树高、胸径、单株材积生长量、木材基本密度和红心材比例分别达到12.63 m、15.2 cm、0.136 8 m³、0.328 0 g/cm³和40.76%。参试家系所有性状的遗传方差均达到统计学极显著差异水平,候选群体中存在真实的遗传差异。家系树高、胸径和单株材积狭义遗传力分别为0.246、0.358和0.329,家系内最优单株树高、胸径及单株材积狭义遗传力分别为0.464、0.687、0.680。以12 a材积生长量性状为优选基准,兼顾木材基本密度和红心材比例,进行优良家系和家系内优良单株的综合选择,筛选出10个速生全同胞家系,其平均树高、胸径、单株材积、基本密度和红心材比例分别为13.34 m、17.0 cm、0.176 3 m³、0.320 2 g/cm³ 和40.76%。入选家系平均材积遗传增益幅度为6.14%~21.60%。中选的19个优良个体的材积生长量遗传增益幅度为58.62%~178.20%(平均为83.12%)。12年生最优家系木材基本密度达0.363 3 g/cm³,家系内最优单株木材基本密度最高达0.476 4 g/cm³。19个中选优良单株的材积平均遗传增益为83.12%,木材基本密度提高10%以上,红心材比例提高12.78%。这批材积生长量遗传增益突出,木材基本密度高,红心材比例高的优良家系和优良单株,不但是营建第4代种子园重要亲本来源,而且也是优良无性系培育和推广应用的重要遗传资源基础。本研究还对家系的树高、胸径和材积生长量稳定性、选择率对遗传增益的影响,以及家系材积生长量早晚相关及其早期选择年龄等进行了分析。结果表明,以材积为生长量的综合指标,家系选择率15%时,无论4、5还是6 a时的早期选择结果,与12 a选择入选家系的符合度与遗传增益均达到最高值。这说明杉木第4代遗传改良中,据4~6 a幼林的材积生长表现开展早期选择,不仅可行有效,还大幅度节约了时间,缩短了育种周期。【结论】 杉木第4代遗传改良的1个候选群体在生长发育和木材性能方面存在丰富的遗传变异。这些在材积生长量、基材密度和红心材比例等方面遗传增益较高的优良亲本和重选优良个体不仅是杉木第4代种子园建立的重要亲本来源,还是杉木优良无性系选择的重要遗传资源。

Performances and selections on a 12-year-old full-sib progeny testing from one of the candidate population for the 4th generation Chinese fir breeding

【Objective】To develop new genetic resourese and establishment techniques of the next generation seed orchard, the 4th generation candidate genetic populations of chinese fir (Cunninghamia lanceolata) (which was one part of the long term Genetic Improvement Program of Chinese fir, organized by the Nanjing Forestry University-Fujian Province Cooperative)were created by a series of planed intraspecific crossing, and then the full-sib progeny testing and traits evaluation has been conducted continuously, since 2006. The establishment of the 4th generation orchard for seed production were initiated in 2016. In this study, a 12-year-old full-sib progeny testing was investigated and analyzed systematically, to provide detail genetic information and excellent parents selected for the 4th generation seed production orchard. 【Method】The tree height of 1-12 a, diameter at breast height (DBH) of 4, 5, 6, 9 and 12 a of full-sib progeny testing was measured, and the average volume per tree by family was calculated. The best individual trees within all the family plot were selected, and the wood increment core samples were collected at DBH (1.3m) to determine basic wood density and dark-brown heartwood proportion. The annual mean value and coefficient of variation on growth traits were used to evaluate the stability of family growth traits. The genetic variance and heritability was estimated for all observed traits. The effects of different stand ages, different effects of selection proportion and early selection on the accuracy and genetic gain was compared year by year, respectively. Finally, the excellent full-sibling families and superior individual trees within the family was selected and the genetic gain to be predicted, combining with their single tree volume and wood character.【Result】1) The results showed that the family mean of the tree height, DBH, volume growth (single tree), wood basic density and the proportion of dark-brown heartwood was 12.63 m, 15.2 cm, 0.136 8 m³, 0.328 0 g/cm³ and 40.76%, respectively. The genetic variance was extremely significant statistically for all the characters in the testing, and it was means that the true genetic differences was existed in the 4th candidate populations. 2) The family narrow heritability was 0.246, 0.358 and 0.329 for tree height, DBH and single tree volume, and it was 0.464, 0.687 and 0.680 for re-selected elite trees, respectively. Based on the optimization benchmark of volume growth, and basic wood density and the proportion of dark-brown heartwood, 10 excellent families and 19 elite trees within the family were selected. 3) The mean was 13.34 m, 17.0 cm, 0.176 3 m³, 0.320 2 g/cm³ and 40.76% for tree height, DBH, single tree volume, wood basic density and proportion of dark-brown heartwood of selected family, respectively. The volume genetic gain was 6.14%-21.60% for selected families, and 58.62%-178.20% for 19 excellent single trees. The mean of wood basic density was 0.363 3 g/cm³ for selected families, and 0.476 4 g/cm³ for the best selected individual. It was increased by 10% and 12.78% over the family mean for basic wood density and proportion of dark-brown heartwood traits. 4)The stability of tree height, DBH and volume growth, effects of selection proportion on genetic gain, early-later correlation of volume growth and early selection ages was also analyzed comprehensively. Setting volume growth as a comprehensive trait of tree height and DBH, and family selection proportion at 15%, the conformity degree of the selected family and the genetic gain for volume growth was the highest at 12 a, whatever the early selection was processed in 4, 5 or 6 a. This indicates that the early selection based on the volume growth performance of juvenile plantation, is not only feasible and effective in the 4th generation of genetic improvement of Chinese fir, but also the breeding cycle could be reduced greatly. 【Conclusion】there were abundant genetic variations on growth and wood properties from one candidate population for the 4th generation genetic improvement of Chinese fir. And these excellent families and re-selected elite individuals with a higher genetic gain in volume growth, basic wood density and proportion of dark-brown heartwood are important parental sources for the 4th generation seed orchard establishing, and also the genetic resourese of excellent clonal selection in the next rotation of genetic improvement of Chinese fir.