Search

Conifers are long-lived and slow-evolving, thus requiring effective defences against their fast-evolving insect natural enemies. The copy number variation (CNV) of two key acetophenone biosynthesis genes Ugt5/Ugt5b and βglu-1 may provide a plausible mechanism underlying the constitutively variable defence in white spruce (Picea glauca) against its primary defoliator, spruce budworm. This study develops a long-insert sequence capture probe set (Picea_hung_p1.0) for quantifying copy number of βglu-1-like, Ugt5-like genes and single-copy genes on 38 Norway spruce (Picea abies) and 40 P. glauca individuals from eight and nine provenances across Europe and North America respectively. We developed local assemblies (Piabi_c1.0 and Pigla_c.1.0), full-length transcriptomes (PIAB_v1 and PIGL_v1), and gene models to characterise the diversity of βglu-1 and Ugt5 genes. We observed very large copy numbers of βglu-1, with up to 381 copies in a single P. glauca individual. We observed among-provenance CNV of βglu-1 in P. glauca but not P. abies. Ugt5b was predominantly single-copy in both species. This study generates critical hypotheses for testing the emergence and mechanism of extreme CNV, the dosage effect on phenotype, and the varying copy number of genes with the same pathway. We demonstrate new approaches to overcome experimental challenges in genomic research in conifer defences. [ABSTRACT FROM AUTHOR]

The demand for exterior wood siding is stagnating in North America due in part to perceptions of low durability and the need for frequent maintenance. One way to address these concerns is to modify the wood to improve its physical properties, while maintaining its appearance. In this study, white spruce was treated with organosilanes and a combination of aluminum treatments followed by a thermal treatment to improve the dimensional stability and the wood durability. Anti-swelling efficiency (ASE), leaching and decay tests were performed on the treated Canadian wood species. The quantity of hydroxyls available after treatment was evaluated by water vapor sorption. The results showed that the treatment improved the dimensional stability up to 50%. Available hydroxyls decreased by as much as 37%. The organosilanes treatment was resistant to leaching, while the aluminum was observed to leach. Organosilanes in combination with aluminum showed brown rot resistance. The addition of aluminum to the organosilanes treatment did not have effect on dimensional stability but it had a great impact on the brown rot resistance. [ABSTRACT FROM AUTHOR]

• We exposed seedlings of conifer species to three realistic simulated future climates. • Seedlings of conifer species experienced high mortality (75%) induced by drought. • Conifer species are highly vulnerable at the seedling stage to future drought. • Hydraulic safety margins are good indicators of mortality risk for conifer species. The future climate of northern temperate forests is projected to be drier and warmer by the end of this century. As a result, more drought-induced forest dieback events are anticipated in northeastern North America, and assessing the vulnerability of dominant tree species to drought is critical for understanding the future composition of these forests. In a greenhouse experiment, we exposed two-year-old seedlings of Picea glauca (Moench) Voss, Picea mariana (Mill.) B.S.P. and Pinus strobus L. to three future climate treatments for southern Quebec, Canada, and evaluated their mortality, growth, and foliage water status responses to soil water availability and atmospheric drought. Using a unique approach, climate treatments emulated droughts of different frequencies, durations, and intensities. Treatments closely simulated one growing season, with changes in air temperature and relative humidity every six hours and daily adjustment in the amount of water delivered to the seedlings. The three species experienced high mortality (75%) in all water-limited treatments compared to a control treatment that provided non-limiting soil moisture (0% mortality). The biomass of the seedlings that survived was 40% lower than that of control seedlings. Our results confirmed that the hydraulic safety margins, defined as the difference between seasonal minimum water potential and xylem water potential leading to 12, 50 and 88% of hydraulic conductivity loss, were good predictors of probability of tree mortality. Therefore, hydraulic safety margins are useful functional traits that can be used to compare the vulnerability of various species to drought and then provide crucial information to practitioners and policymakers to adjust forest management to climate change. We showed that three dominant conifer species of northern temperate forests were highly vulnerable to drought in future climates. Because drought is projected to be a significant threat to forests, understanding potentially adaptive physiological responses to drought, such as hydraulic safety margins of tree seedlings, is important for predicting the response of forest regeneration and composition in warmer and drier climates. [ABSTRACT FROM AUTHOR]