Assessing the Potential for Hybrid Vigour Within a Species: Disparate Population Breeding of Balsam Poplar

• Author / Creator

  Hu, Yue

• When two or more species are crossed to produce hybrid progeny, some of them can be expected to yield a growth performance far superior to that of either parent (i.e., hybrid vigour/heterosis). To date, there have been few attempts to examine whether hybrid vigour can be achieved by crossing disparate populations of the same species. Balsam poplar (Populus balsamifera L.) is a widespread tree species in North America ranging from Alaska to Newfoundland. This wide range makes it an ideal species to study within-species hybrid vigour for increasing genetic gain in growth.
  In this thesis project, I tested the hypothesis that within species breeding of widely-spaced populations of balsam poplar leads to the expression of hybrid vigour through the following mechanisms: 1) A longer growing season due to phenology differences, which leads to increased growth; and 2) Differences in endogenous hormone levels that are linked to physiological performance. In addition, I explored epigenetic responses of hybrid balsam poplar to abiotic environmental stress.
  In September 2009, three balsam poplar field trials (two in Alberta (AB) (Field AB1 and AB2 respectively) and one in Quebec (QC) (Field QC1)) were established. Five male parents from each province with five female parents from Quebec, and four female parents from Alberta were used for breeding, both for within-region and between-region crosses. Preliminary analysis on six-year height and diameter data from AB1 and AB2 indicated differences in family performance among the different cross-types (within- and between-region crosses). The results from this project showed that the AB♀ × QC♂ cross-type ranked first for height and diameter at breast height (DBH). From phenology study (Chapter 2), the increased growth of hybrid balsam poplar was due to phenological differences (earlier bud burst and often a later bud set). From the hormone study (Chapter 3), results showed stem volumes calculated from height and diameter of 2-month-old rooted cuttings grown under optimal greenhouse conditions are positively and significantly correlated with stem volumes of 8-year old field-grown trees. Additionally, hybrid vigour is correlated with hormone levels and linked to photosynthetic performance. The epigenetics study (Chapter 4) suggested that fast growing (FG) progeny originating from sources in AB were more resistant to drought than the same genotypes originating from wetter locations. Additionally, cuttings of the same genotype grown in different locations showed different responses under well-watered versus drought conditions. Therefore, epigenetics at the phenotypic level of measurement was successfully detected.
  My study demonstrated the potential of using disparate, native populations of balsam poplar to produce superior progeny with enhanced stem growth traits. However, future use of this material on crown land for reforestation or reclamation purposes may require additional field testing to meet policy regulations.

• Subjects / Keywords

  • Heterosis
  • Balsam poplar
  • Phenology
  • Hormone
  • Epigenetics
  • Tree improvement

• Graduation date

  Fall 2021

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/r3-cabr-ha78

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.