Selective breeding for growth does not compromise drought resistance in western larch seedlings

Abstract

As the impacts of drought intensify with climate change, adaptation to drought is becoming an increasingly important consideration for tree breeding and forest management. This elevates the need to understand how breeding for faster growth affects drought tolerance and if breeding to improve drought tolerance could help mitigate the impacts of drought on forest health and productivity. To understand the implications for tree breeding in future climates, we studied how selective breeding of western larch (Larix occidentalis) for faster growth affects drought resistance (a component of drought tolerance); the quantitative genetics of drought resistance traits; and the effects of drought on genetic variation in growth and phenology. We established a seedling common garden experiment in a warm climate outside the natural range with 23 natural populations and 29 selectively-bred families from two breeding zones in British Columbia. We imposed two drought treatments of varying duration and severity with a control treatment in the third growing season. Height growth, bud phenology and drought resistance traits were phenotyped. We found that selective breeding for faster growth has not compromised drought resistance in seedlings. Weak correlations between drought resistance and height growth or bud phenology among family phenotypes suggest that breeding for improved drought resistance may be possible without affecting other traits relevant to adaptation to local climates. However, we detected limited genetic variation and low heritability for drought resistance, as well as diminished genetic variation in growth and phenology traits under drought, indicating potential barriers to breeding for improved drought resistance in seedlings.

Citation

Roskilly, Beth A.; Henry, Martin R.; Aitken, Sally N. 2025. Selective breeding for growth does not compromise drought resistance in western larch seedlings. Forest Ecology and Management. 596: 123064. https://doi.org/10.1016/j.foreco.2025.123064.