Ref ID: 11025
Ref Type: Thesis/Dissertation
Author: Huang, Shaowei
Degree: PhD
Type:
Num Pages:
Submission Date: 25-5-2004
Acceptance Date: 6-6-2004
Supervisors:
Institution: South China Agricultural University
Department: College of Life Sciences
City: Guangzhou
Keywords: affected/AFLP/allele/Australia/bark/basic density/branch/branch angle/branch architecture/breeding/CAD/characteristic/clone/comparative/comparative mapping/conservation/conservation genetics/control/conventional/cross/data/dbh/density/diameter/dry/early/effect/estp/expression/F1/F2/family/forest/forest tree/forestry/form/gain/gene/genetic/genetic control/genetic maps/genetics/genome/genotype/growth/height/high/homologous/hybrid/hybrid pines/hybrids/importance/inbreeding/index/industry/initiation/intensive/juvenile/length/linkage map/loci/map/marker/marker-aided selection/MAS/microsatellite/model/models/molecular/molecular genetics/molecular marker/molecular markers/negative/P/pal1/parent/pattern/phenotype/pine/Pinus/Pinus caribaea/Pinus elliottii/Pinus taeda/plant/planting/polymorphism/population/post-planting/practice/production/progeny/progeny test/property/QTL/QTL mapping/quality/quantitative/quantitative genetics/Queensland/rate/research/roguing/root/rooting percentage/scientist/seed/selection/sequence/solid/species/SSR/stem/strike rates/study/test/theory/thickness/trait/tree/trees/variance/wood/wood properties
Abstract: Two populations of an outbred F1 family and one population each for two inbred F2 families of Pinus elliottii var. elliottii (PEE) „e P. caribaea var. hondurensis (PCH) were used in the studies of QTL mapping and marker-aided selection for characteristics of economic importance in the hybrids. Molecular markers involved include microsatellite (SSR), expressed sequence tag polymorphism (ESTP)¡Aa phenylalanine ammonia-lyase (PAL1) gene and a cinnamyl alcohol dehydrogenase (CAD) gene. The study was summarized as follows. 1. A F1 population consisted of 86 individuals from a cross of a female parent of PEE and a male parent of PCH was used to construct comprehensive linkage maps for both of the parents, with ESTP, SSR, AFLP, CAD and PAL1 markers. The PEE parental map consisted of 68 SSR, 82 AFLP, 3 ESTP and the CAD markers in 27 linkage groups, with a total length of 1332 cM (Kosambi) and an average marker interval of 10.7¡Ó6.8 cM. It was estimated to cover 93% of the whole genome. The PCH parental map consisted of 70 SSR, 125 AFLP, 3 ESTP and the PAL1 markers in 32 linkage groups, with a total length of 1734 cM (Kosambi) and an average marker interval of 10.6„b7.8 cM, and was estimated to cover 92% of the whole genome. 2. High level of synteny was identified between maps of the two parents and among maps of PEE, PCH and loblolly pine (Pinus taeda). 37 SSR were shared by both of the parental maps and 15 homologous linkage groups were identified. Synteny and collinearity of the maps were identical in all homologous groups. 13 of the 15 homologous groups were also homologous with a SSR linkage map of loblolly pine. Besides, they shared 6 ESTP and SSR markers with two other maps of loblolly pine. These comprehensive maps will be a basis of QTL mapping and marker-aided selection for traits of economic importance of hybrid pines. It will also facilitate a further comparative mapping between PEE „e PCH hybrid and other pine species. 3. The above-mentioned mapping population and all markers except AFLP, were used to detect QTLs of growth, form quality and wood characteristics in hybrid pines. All phenotype data were from a two-site progeny test at the age of 7 years. Growth traits involved include height, diameter at breast high (DBH), bark thickness, ring width, earlywood ring width, latewood ring width and dry wood mass index. Form quality traits include stem straightness (stem class), ramicorns, Double leaders, and some branching traits. Wood properties include whole-core basic density, average ring density, earlywood ring density and latewood density. All traits for radial growth, wood mass index and wood density were separated to both average and annual basis. Totally there were 49 traits included in the study of QTL mapping. 4. Most of the studied traits were associated with several QTLs and most of the QTLs performed in oligogenic model. Loci explaining more than 20% of the phenotypic variance were identified for many traits. Wood density traits were genetic controlled at a higher level than growth traits. Level of genetic control on branching traits was about the same as that of growth traits. The highest level of genetic control was detected on average branch angle (AVBRA). QTLs of growth traits mainly concentrated on a few linkage groups and so did that of wood density traits. Two linkage groups played key effect in the genetic control of both growth and wood traits. Parts of the QTLs for these two sets of traits clustered on two small groups and showed pleiotropism models. 5. Based on the previously done QTL mapping for strike rate of adventitious root initiation of 3-year-old hedges (by research scientists and fellows in Cooperative Research Centre for Sustainable Production Forestry, Australia, involving cooperative organizations include Centre for Plant Conservation Genetics, Southern Cross University, Queensland Department of Primary Industries, Forestry and the University of Queensland), through an outbred F1 population consisted of 224 clones and an inbred F2 population consisted of 192 clones. A third inbred F2 population consisted of 26 clone was also used to confirm the QTL effect. Evident oligogenic model had been determined for QTLs of strike rate. Predominant additive effects were detected in all loci. Gene expression was stable across genetic backgrounds and at different degrees of inbreeding. Species effect was evident. At most of the loci, PCH contributed alleles for high strike rates. On the other hand, PEE can provide few favorable alleles as well. The fact that alleles of QTLs for strike rate expressed stably across populations of different genetic background, and the existence of species effect, provided a solid basis to marker-aided selection for the trait. 6. QTLs of strike rate influenced the growth within 2 years post planting, but the effects became weak beyond 4 years post planting. There was no significant negative correlation between strike rate and the growth beyond 4 years post forestation, indicating MAS for strike rate would not cause decrease in growth. 7. A few traits of form quality (stem straightness and double leaders) shared several QTLs with strike rate. Species effect was also evident. However, the QTLs affected stem forms in the opposite direction to that they affected strike rate, i. e. PEE alleles were favorable to stem forms but unfavorable to strike rate compared to PCH alleles. Therefore, intensive selection on strike rate could cause decrease in form quality. 8. Strike rate of mature hedges (6 years old from seed) and that of juvenile hedges (less than 3 years from seed) shared the same QTLs. Although the strike rate of 6-year-old hedges decreased severely because of maturation effect, QTL effects were still evident. Directions of species effect were the same and the predominance of additive effect over dominant effect was stronger than what happened to 3-year-old hedges. Therefore, gains from selection at the age of 3 years would maintain to the age of 6 years. 9. Practical selection was conducted for root strike rate, through multiple scenarios using several markers associated with QTLs of strike rate. Selection effects of all scenarios were compared. It was demonstrated that effects of multiple marker selections were better than those of single marker selections. Effects of selecting ¡§superior¡¨ genotypes were better than those of roguing ¡§inferior¡¨ genotypes. However, the number of markers used in MAS should not be more than 3, given the existence of large effect loci. Practice has showed that MAS can simultaneously increase the strike rate of both juvenile and mature hedges and the early growth as well. Meanwhile, form quality would decrease if intensive selection is adopted. Although the existence of individual of high strike rate (100%) and good stem straightness (6% higher over the mean of population), a selection of moderate intensity was recommended. Scenarios combining QTLs for multiple traits or multiple sorts of traits should be considerable if possible. 10. The phenomena and patterns on the genetic control of traits of economic importance in hybrid pine revealed by the studies, involved some important aspects of quantitative genetics and molecular genetics of forest tree. The results were believed to enrich the genetic theory of pine trees and provide a valuable reference to the conventional and molecular assistant breeding of hybrid pines
Notes: Entered by Mervyn Shepherd (25/03/2005)
Address: mshepher@scu.edu.au
Reprint: Not in File
Program: SPF Genetic Improvement
Project: A7
Deliverable: A7-3
Confidentiality: Confidential to Queensland Department of Primary Industries Forestry, Queensland Forest Research Institute, Southern Cross University, University of Tasmania, CSIRO Forestry and Forest Products
Availability:
Report: Annual Report 2004/5