Growth, stability, and genotype x environment (GxE) interaction were investigated for 69 clones after five years at six sites in Minnesota. Fifty-three clones were Populus deltoides x Populus nigra (DxN) crosses, nine were P. deltoides x P. maximowiczi, ten other crosses. Most clones were previously screened for growth and disease resistance in Minnesota. Five-year diameter (DBH) and basal area (BA) at 1.38 m averaged 93.5 mm and 72.11 cm2, respectively, over the six sites. DBH site means varied from 109.0 to 79.4 mm. The fastest-growing clone BA was 64% and 49% larger than the mean of the two commercial standards and the mean of the population, respectively. Site, clone, and clone x site effects were highly significant in the ANOVA. The variance component for clone was over twice that of clone x site (GxE), indicating a relatively small reduction in genetic gain due to GxE. Clonal rank did not change between sites. GxE interaction was dominated by relative performance differences of clones on the different sites. Twenty-six percent of clones were stable (little change in growth between sites), 74% unstable. Stability coefficients of the unstable clones varied over a 99% range, indicating the population had high and variable phenotypic plasticity. Only 15% of clones were both stable and fast growing. Seven putatively superior clones, all DxN, were selected for future testing under near-commercial conditions. The results, if representative of other inter-specific Populus populations, suggest it will be difficult, and probably impractical, to reduce GxE with standard quantitative genetics methods in hybrid poplar tree improvement programs without sacrificing productivity gains.
Bibliographical noteFunding Information:
This work was funded by the State of Minnesota appropriations to the Minnesota Hybrid Poplar Research Cooperative (MHPRC) , State Special appropriations to the University of Minnesota Duluth Natural Resources Research Institute , Minnesota Agricultural Utilization Research Institute , US DOE BETO Sun Grant Initiative Poplar Woody Crops Program contract # DEFC36-05GO85041 , US DOE Idaho National Laboratory contract #184125 , USDA NIFA Agriculture and Food Research Initiative Competitive Grants Program Sustainable Bioenergy and Bioproducts Challenge Area grant #2018-68005-27635 , and the following companies through membership in the MHPRC : Verso Corporation, International Paper, Boise Cascade, Potlatch Corporation, UPM-Blandin, and Minnesota Power. The authors acknowledge and thank Verso Corporation's forestry staff for providing land and assistance with site selection, planting, and maintenance throughout the field-testing periods of these trials. Clones from outside our program were provided by the U.S. Forest Service Rhinelander Forestry Sciences Laboratory (Dr. Don Riemenschneider). Parents from outside our program used in producing inter-specific hybrids were from the University of Minnesota (Dr. Carl Mohn program), GreenWood Resources (Dr. Brian Stanton), University of Toronto (the late Dr. Louis Zsuffa), and Iowa State University (the late Dr. Rick Hall). Kim Rewinkel and Anda Bellamy are gratefully acknowledged for editing the paper for journal submission.
- Forest genetics
- Genotype x environment
- Hybrid poplar
- Tree improvement