Genetics Research

Hybrid poplars are one of the primary dedicated energy crops needed to meet national targets for bioenergy in the USA (US DOE, 2016). However, investments in hybrid poplar programs are not expected to support narrow breeding zones or the tailoring of individual clones to specific sites (Nelson et al., 2018), ie., specialist genotypes (Zalesny et al., 2009). Accordingly, the emphasis of our hybrid poplar breeding program at the Natural Resources Research Institute (NRRI) has evolved so that it is now identifying families and clones that are fast-growing and broadly adapted to a range of soils, climates and geographic regions, ie., generalist genotypes (Zalesny et al., 2009).

The NRRI program has produced many promising native cottonwood and poplar hybrids that are in various stages of testing. The best clones show at least a 60 - 70 percent genetic gain in volume growth over existing commercial standards (Berguson et al. 2015; Nelson et al. 2018; Nelson et al. 2019).

However, no clones are ready to be released for commercial use in the Midwest due to: 1) inconsistent performance on different sites (high GxE); 2) the need for a suite of a minimum of 6–10 genetically diverse superior disease resistant clones; 3) inadequate testing outside Minnesota; and 4) lingering questions about disease resistance. These limitations are targeted in our current research.

Current research activities include the following:

  • Testing of improved clones in north central Minnesota, central Iowa, and southwestern Indiana, with a goal of identifying broadly-adapted clones. Ideal clones will show consistent performance (low GxE) on sites in all 3 states and superior disease resistance.
  • Testing of new genetic material in north-central Minnesota.
  • Monitoring previous hybrid poplar studies to identify elite broadly adapted, disease resistant .and fast growing families and clones and to accurately predict biomass yields.

Recently published data from existing field tests include early growth rate and disease resistance data for Minnesota sites for some of the genotypes to be included in this study (Nelson et al. 2018), and recently completed field test results for two sites in Indiana that indicate unexpectedly high growth rates and plasticity of adaptability (low GxE) for our DxN genotypes derived from material of Minnesota origin (Nelson et al. 2019). Furthermore, a paper published in Silvae Genetica in 2017 (Berguson et al. 2017) indicates that the NRRI recurrent breeding and selection strategy that gives weight to both families and clones within families is sound and can be optimized. Results of this research are being used to design the most efficient breeding program and estimate yield gains possible over successive breeding cycles.

References Cited

Berguson, W.E., Buchman, D., Rack, J., Gallagher, T., McMahon, B., and Hedke, D. 2015. Laurentian Bioenergy Project. DOE Technical Report DOE-UM-GO86023-1. 290 p.

Berguson, W.E., B.G. McMahon, and D.E. Riemenschneider. 2017. Additive and non-additive genetic variances for tree growth in several hybrid poplar populations and implications regarding breeding strategy. Silvae Genetica 66: 33 – 39.

Nelson, N.D., W.E. Berguson, B.G. McMahon, M. Cai, and D.J. Buchman. 2018. Growth performance and stability of hybrid poplar clones in simultaneous tests on six sites. Biomass and Bioenergy. 118: 115 – 125.

Nelson, N.D., R.M. Meilan, W.E. Berguson, B.G. McMahon, M. Cai, and D. Buchman. 2019. Growth performance of hybrid poplar clones on two agricultural sites with and without early irrigation and fertilization. Silvae Genetica 68: 58 -66.

U.S. Department of Energy (US DOE) (2016) 2016 Billion-Ton Report: Advancing Domestic Resources for a Thriving Bioeconomy. In: Langholtz MH, BJ Stokes and LM Eaton (Leads) Volume 1: Economic Availability of Feedstocks. Oak Ridge, TN: ORNL/TM-2016/160, Oak Ridge National Laboratory. http://doi.org/10.2172/1271651

Zalesny R.S., R.B. Hall, J.A. Zalesny, B.G. McMahon, W.E. Berguson and G.R. Stanosz (2009) Biomass and genotype x environment interactions of Populus energy crops in the Midwestern United States. BioEnergy Research 2:106-122. https://doi.org/10.1007/s12155-009-9039-9