Quantitative genetic architecture of adaptive phenology traits in the deciduous tree, Populus trichocarpa (Torr. and Gray)

Abstract

In a warming climate, the ability to accurately predict and track shifting environmental conditions will be fundamental for plant survival. Environmental cues define the transitions between growth and dormancy as plants synchronise development with favourable environmental conditions, however these cues are predicted to change under future climate projections which may have profound impacts on tree survival and growth. Here, we use a quantitative genetic approach to estimate the genetic basis of spring and autumn phenology in Populus trichocarpa to determine this species capacity for climate adaptation. We measured bud burst, leaf coloration, and leaf senescence traits across two years (2017–2018) and combine these observations with measures of lifetime growth to determine how genetic correlations between phenology and growth may facilitate or constrain adaptation. Timing of transitions differed between years, although we found strong cross year genetic correlations in all traits, suggesting that genotypes respond in consistent ways to seasonal cues. Spring and autumn phenology were correlated with lifetime growth, where genotypes that burst leaves early and shed them late had the highest lifetime growth. We also identified substantial heritable variation in the timing of all phenological transitions (h2 = 0.5–0.8) and in lifetime growth (h2 = 0.8). The combination of additive variation and favourable genetic correlations in phenology traits suggests that populations of cultivated varieties of P. Trichocarpa may have the capability to adapt their phenology to climatic changes without negative impacts on growth.

The genetic basis of adaptation in phenology in an introduced population of Black Cottonwood (Populus trichocarpa, Torr. & Gray)

“…6 Putative candidate genes in introduced population and native North American range. Overlap between our (a) autumn phenology and (b) spring phenology (bud burst) candidate genes and those identified in two other studies (Evans [ 22 ] and McKown [ 16 ]) …”

“…In northern Europe, biomass production with Populus species is an underutilized option due to the phenological maladaptation of commercially bred varieties [ 21 ]. Commercial interest thus exists for adapting non-native Populus species to growth under northern European conditions, but the required genetic resources and understanding of relevant traits for such an undertaking are lacking [ 22 ]. Black cottonwood ( Populus trichocarpa ) is a deciduous tree native to North America with continuous distribution in western and northwest North America from California to Alaska.…”

“…Introduction of the species to novel conditions such as those characterizing northern Sweden allow further exploration of the genetic architecture of these traits, and have the potential to reveal novel genes associated with them and comparisons with the results and signatures of selection from the natural range present an opportunity to uncover further details of adaptation, and potential constraints of it in the novel conditions, in these traits. Finally, exploration of the adaptive potential [ 22 ] and its genetic basis in small populations resulting from introductions will also offer insight into how to perform cost-effective breeding in forest trees in terms of breeding population size.…”

Theory into practice: opportunities & applications of quantitative genetics in plants

“…The challenge of adapting crops to changing climates is discussed for wheat (Hyles et al 2020) and the perennial tree species Populus trichocarpa (Richards et al 2020). Both argue that there is much value in characterising component genetic controllers of the seasonal timing of plant lifecycles, given its central importance in seasonal adaptation and for optimising crop production in a changing climate.…”

“…Understanding the underpinning genetics and accurately characterising corresponding phenotypes is central to future breeding efforts. Richards et al (2020) describe adaptive phenology in the perennial tree species P. trichocarpa, incorporating the pressing need to predict and track environmental change, particularly in the breeding and selection of perennial species. Supporting this, they determine the quantitative genetic basis of a number of phenology traits, demonstrating a consistent year-to-year response to seasonal cues.…”