关键词: 杉木, 第4代育种候选群体, 全同胞子代测定, 遗传增益, 早期选择

Abstract:

【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.

Key words: Chinese fir(Cunninghamia lanceolatea), the 4th generation breeding candidate population, full-sib progeny testing, genetic gain, early selection