- Date de réalisation : 27 Janvier 2020
- Durée du programme : 22 min
- Classification Dewey : SCIENCES nature - Botanique Arbres, Arbustes, Plantes grimpantes
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[COLLOQUE] GENTREE Final Conference 27-31 January 2020 séance 21
GENTREE Final Conference :
Ian MACLACHLAN - University of British Columbia Vancouver · Canada
GENTREE Final Conference 'Genetics to the rescue - managing forests sustainably in a changing environment'
27-31 January 2020, Avignon, France
Ian MACLACHLAN - University of British Columbia Vancouver · Canada : Selective breeding produces multi-locus responses in adaptive genomic variation of lodgepole pine
Climatic adaptation of temperate and boreal trees involves trade-offs between growth, phenology and tolerance to cold.
Negative trade-offs among these traits have evolved in natural populations and can be exacerbated by selective breeding programs.
Understanding the genomic basis of climatically adaptive traits and their trade-offs may allow efficient and precise adaptive genetic management strategies in response to shifting climates, and provide insights into the genomic architecture of adaptive traits.
Our study combined seedling phenotypes (n = 2176) for height growth, phenology and cold injury traits, genotype data for 18,600 SNPs from previous exome captures, and climatic data for 20 selectively bred and 105 wild-stand lodgepole pine seedlots sampled from across Alberta and British Columbia, Canada.
GWAS was used to identify phenotype-associated SNPs of interest. We then quantified multi-locus effects of selective breeding at individual seedling and population levels by studying frequency changes in alleles associated with the greater trait value for each phenotype-associated SNP, which we termed ‘positive effect alleles’ (PEAs).
There was substantial overlap among all traits in SNPs that had the strongest phenotypic associations, suggesting widespread pleiotropy is important to climatically adaptive trade-offs among traits despite their strongly contrasting genomic architectures.
Selective breeding for increased height growth caused systematic PEA frequency increases within seedlings for SNPs associated with height, phenology and cold injury.
Genomic responses to selective breeding varied substantially among regions of our sampled range and appear linked to differences in genomic architectures among traits.
Modest amounts of multi-locus variation in breeding zone PEA frequencies was associated with strong phenotypic differences and climatic gradients for both natural and selectively bred seedlings, reinforcing the need for assisted gene flow to mitigate climatic maladaptation.
Selectively bred seedlings had stronger phenotype-genotype relationships than natural seedlings among breeding zones for three of four traits, and for all the climate-genotype relationships, even though these differences were not statistically significant.
Relationships among genotypes, phenotypes and climate were maintained or strengthened among the selective breeding programs we sampled, suggesting that among breeding zones the same assisted gene flow prescriptions are valid for both natural and selectively bred seedlings.
Even so, the potential for trade-offs among traits due to substantial antagonistic pleiotropy was evident and should be carefully monitored as a potential source of climatic maladaptation in selectively bred seedlings.
Our use of PEA frequencies demonstrated a simple, sensitive and effective method of summarizing genomic data for polygenic traits and detecting the effects of selective breeding on climatically adaptive genotypes that are relevant to breeding strategies and assisted gene flow policies.