Stability of Douglas-fir genotypes across temperature and moisture regimes: Implications for breeding and climate change Sally N. Aitken and Tongli Wang Department of Forest Sciences University of British Columbia

Breeding for stability Genotype-by-environment interaction complicates selection and reduces genetic gain Breeders seek predictable genotypes with ‘stable’ performance across the range of potential deployment environments within breeding zones Climate change (changes in temperature and moisture regimes) will result in novel environments

What is stability? Varying definitions Type 1: Genotype with small among- environment variance in phenotype (b<1.0) Type 2: Regression of performance against site mean performance has average slope (b  1.0) Type 3: Deviation from regression mean square as small as possible (high r 2 )

Types of stability b=1 b=0 r21r21 b=1 r 2< 1

Objectives What environmental factors result in g x e? What are the growth and physiological characteristics of stable genotypes? Can stable genotypes be selected from field tests? How will select genotypes react to new climatic conditions?

Selection of stable and unstable parents 12-year stem volume data analyzed from 12 progeny test sites for 372 parents in 62 six- parent diallels 8 pairs of parents selected with similar breeding values (>0) but contrasting contributions to genotype-by-environment variance component for diallel (Type 3 stability) Two or three full-sib families for each parent included in experiment (total of 45 full-sib families)

1-year-old seedlings planted into raised nursery beds 4 treatments applied, 2 x 2 factorial with soil temperature (ambient and warm) soil moisture (well watered and drought) Temperature in warm treatment 3 to 4 o C above ambient Drought treatment had minimum predawn water potential of mPa

Treatment means All treatments differ significantly (Duncan’s multiple range test; p<0.05)

The progeny of stable and unstable parents had different average norms of reaction 1998 height increment (mm)

Stable and unstable families differed significantly in their response to treatments Cool Warm Wet Dry Stable Unstable

Analysis of Variance - F values for treatments, stability and interactions

Cold hardiness and stability Fall cold hardiness differed significantly among moisture treatments (p<0.05) There was no sig. stability effect or stability-by-treatment interaction for cold hardiness

Selecting for stability in Douglas-fir ‘Stable’ families selected for Type 3 stability exhibit type 2 stability ‘Unstable’ families selected for Type 3 stability exhibit both Type 3 instability across all treatments and Type 1 stability for temperature Norms of reaction for temperature appear to vary more than those for moisture ‘Stable’ ‘Unstable’

Reaction norms for temperature The unstable parents selected produce progeny with higher mean growth rates under poorer growth conditions (lower temperature and moisture) However, whether unstable genotypes have Type 1 stability (consistent performance) at higher temperatures depends on the norms of reaction to temperatures above those tested UnstableStable Low test temp. High test temp.

Conclusions Douglas-fir families contributing to genotype-by- environment interaction in field trials are less responsive to soil temperature than stable families but respond similarly to soil moisture Families with low Type 3 stability may be more productive on poor field sites than families with high Type 3 stability Deploying mixtures of genotypes with varying norms of reaction to temperature may be an appropriate strategy for uncertain future climates Further research is needed to characterize norms of reaction to soil temperature over a broader range

Acknowledgements Jack Woods, BC Ministry of Forests Alvin Yanchuk, BC Ministry of Forests Sonya Budge, UBC Joanne Tuytel, UBC Glen Reid, UBC Corinne Stavness, UBC