유전간벌 모델에 따른 채종원 개량효과 및 유전다양성 추정 : 상수리나무 채종원을 중심으로 = Genetic gain and gene diversity of seed crops by genetic thinning models in seed orchards : Quercus acutissima seed orchard as a model

다국어 초록 (Multilingual Abstract)

Seed orchards are the main delivery vehicle for tree species' genetic improvement programs where balancing genetic gain and diversity is a main concern. The level of genetic gain or genetic worth of seed orchard crop depends primarily on the genetic superiority of the selected parents, their actual gametic contribution to the resultant seed crops, and the level of gene flow (pollen contamination) from extraneous pollen sources and their respective genetic quality. The genetic diversity of a seed crop is greatly influenced by the magnitude of parental fertility variation (unequal parental contribution to the resulting seed crops) as well as by the level of kinship among the orchard's parental population. Maximum genetic diversity is attained when all genotypes contribute equally to the seed crop while maximum gain depends on the proportionate contribution of high breeding value parents.
In the present study, morphological characteristics and growth traits were surveyed and analysed in a seedling seed orchard of Q. acutissima at ages 10 and 12. Leaves were collected at upper, middle and lower part of clown position from 35 families, and leaf morphology was analysed. As the results, there was a highly significant difference among families, and interaction between family and position was statistically significant. Also significant differences were found between positions in most leaf characteristics except depth of serration, ratio between serration number and leaf length, and leaf area.
The significant differences were found and statistically significant among families and interaction between family and direction (east, west, south and north) where leaves were collected at the middle crown position. But there was no significant difference among directions in the leaf characteristics.
There were highly positive correlations between pollen morphological traits, but the difference among families was not significant. The colpus width was ranged from 1.56㎛ to 1.89㎛. These results are implying that families with bigger polar axis length and equatorial diameter showed larger colpus length and width.
For growth characteristics, the averages of height, DBH, branch height, crown width, branch angle and stem straightness were 9.96m, 14.50cm, 1.04m, 6.80m, 18.82o and 2.58, respectively. Families 075 and 052 showed superior growth in height and 0511 and 0517 were inferior ones. For DBH growth, 075 and 0413 were best families and 0725 and 0511 were inferior families.
Pearson's product moment and Spearman‘s rank correlation coefficients were all positive for all growth traits except branch angle in both 2006 and 2008. This trend was also found in rank correlation. This result showed that the families with good height and DBH growth were also superior in stem straightness.
In ANOVA, there was highly significant difference among families in height, DBH, cylindric volume and stem straightness. Branch height, crown width and branch angle were also significantly different among families.
Family heritability was higher than individual heritability at ages 10 and 12. Height, DBH and stem straightness were under strong genetic control, showing high family heritability. This implies that high genetic gain could be expected by family or individual selection. Breeding values for volume growth were estimated with different weighed values to the growth traits based on ANOVA and genetic variation. This family breeding value was applied as a criterion in the genetic thinning of the seed orchard.
Genetic gain and diversity of orchard crops (acorns) in a seedling seed orchard of Q. acutissima were determined by various thinning schemes (different selection methods and thinning intensities). Different selection methods meant 1) individual selection, 2) family selection and 3) family + within family selection. Effective population size in the seed orchard was estimated by group coancestry. Additionally, gene diversity of acorn in a clone bank of Q. acutissima was monitored for consecutive 8 years based on fertility variation of real observations.
All selection methods gave high genetic gain and reasonable gene diversity. By individual selection, genetic gain increased and gene diversity decreased as selection intensity increased. Under family selection, increase of genetic gain was small at week thinning intensity but it was increased remarkably above 50% thinning intensity. Family + within family selection showed that genetic gain increased as intensity increased and the relative effective population size was decreased up to 30% thinning intensity and kept stable up to 70% thinning and then increased stronger than 70% thinning.
Under all thinning models, the effective population sizes were decreased as thinning intensity was increased, and the difference among thinning models was not remarkable. Up to 50% thinning, individual selection showed the highest effective population sizes but after that, family selection gave the highest values.
Acorn production was surveyed for 8 consecutive years from 2000 to 2007 in the clone bank of Q. acutissima established by grafting from 113 parents in 1992. This data were subjected to the estimation of gene diversity (effective population size) of the acorn produced from the clone bank. The average number of clone that produced acorns was 58 represented 51% of the total number of clones, and it was highest as 78 and 65 in good acorn production years of 2002 and 2005, respectively.
There was 3 or 4 year interval of acorn production in this clone bank. Acorn production reached at peak in 2001 and 2005 and was poor in 2000 and 2004. Coefficient of variation was mirrored to the acorn production.
Cumulative contribution curves (parental balance) to acorn production in good years were more closed to the balancing curve than those in poor acorn production years. Only 20% clone contributed to 80% acorn production in 2000.
Variation of acorn production among clones and the parental balance were connected to the estimation of effective population size. Effective population size of female parent was accompanied with the acorn production, meaning that high effective population size was found in good acorn production.
When data was pooled, the effective population size was 37.6. Thus, loss of gene diversity (gene frequency) could be estimated to be about 1.33% (=1/2Np) in the meta-population that consists of small populations originated from the acorn produced in the clone bank.
In conclusion, various selection methods and thinning intensities should be considered for the genetic thinning of Q. acutissima seed orchard. Under the different thinning models, genetic gain and diversity should be simulated, and then optimal thinning method and intensity must be decided.

목차 (Table of Contents)

• LIST OF TABLES = ⅰ
• LIST OF FIGURES = ⅲ
• ABSTRACT = ⅴ
• Ⅰ. 서언 = 1
• Ⅱ. 연구사 = 5
• 1. 임목의 유전변이 연구 = 5
• 1.1. 엽의 형태적 변이 = 5
• 1.2. 화분의 형태학적 변이 = 6
• 1.3. 생장, 증식 및 종자생산량 변이 연구 = 8
• 2. 채종원 개량효과 증진 및 유전다양성 연구 = 11
• 2.1. 가계(클론)간 종자생산량 및 개화량 변이 = 11
• 2.2. 채종원 개량효과 증진 연구 = 13
• 2.3. 채종원 유효집단크기(유전다양성) 연구 = 14
• 3. 채종원 조성 및 관리방안 연구 = 16
• Ⅲ. 재료 및 방법 = 19
• 1. 공시재료 = 19
• 2. 연구방법 = 20
• 2.1. 가계별 형태적 특성 및 생장량 변이 = 20
• 2.2. 채종원 개량효과 및 유전다양성 추정 = 26
• 2.3. 클론보존원 유효집단크기 추정 = 29
• Ⅳ. 결과 = 31
• 1. 가계별 형태적 특성 및 생장량 변이 = 31
• 1.1. 엽 특성 = 31
• 1.2. 화분의 형태학적 특징 = 33
• 1.3. 생장량 변이 = 36
• 2. 채종원 개량효과 및 유전다양성 = 43
• 2.1. 개체선발 = 43
• 2.2. 가계선발 = 44
• 2.3. 가계 및 가계 내 개체선발 = 46
• 2.4. 간벌모형 간 개량효과 및 유효집단크기 비교 = 49
• 3. 클론보존원 유효집단크기 = 52
• 3.1. 클론 간 종자생산량 변이 및 Parental balance = 52
• 3.2. 기여도 변이에 의한 유효집단크기 추정 = 55
• Ⅴ. 고찰 = 58
• 1. 가계별 형태적 특성 및 생장량 변이 = 58
• 2. 채종원 개량효과 및 유전다양성 = 60
• 3. 클론보존원 유효집단크기 = 63
• Ⅵ. 요약 = 67
• 인용문헌 = 70
• APPENDICES = 88
• PLATES = 99
• 감사의 글