[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

http://www.gentree-h2020.eu/

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-offsbetween growth, phenology and tolerance to cold.

Negative trade-offsamong these traits have evolved in natural populations and can beexacerbated by selective breeding programs.

Understanding the genomicbasis of climatically adaptive traits and their trade-offs may allowefficient and precise adaptive genetic management strategies inresponse to shifting climates, and provide insights into the genomicarchitecture of adaptive traits.

Our study combined seedlingphenotypes (n = 2176) for height growth, phenology and cold injurytraits, genotype data for 18,600 SNPs from previous exome captures,and climatic data for 20 selectively bred and 105 wild-standlodgepole pine seedlots sampled from across Alberta and BritishColumbia, Canada.

GWAS was used to identify phenotype-associated SNPsof interest. We then quantified multi-locus effects of selectivebreeding at individual seedling and population levels by studyingfrequency changes in alleles associated with the greater trait valuefor each phenotype-associated SNP, which we termed ‘positive effectalleles’ (PEAs).

There was substantial overlap among all traits inSNPs that had the strongest phenotypic associations, suggestingwidespread pleiotropy is important to climatically adaptivetrade-offs among traits despite their strongly contrasting genomicarchitectures.

Selective breeding for increased height growth causedsystematic PEA frequency increases within seedlings for SNPsassociated with height, phenology and cold injury.

Genomic responsesto selective breeding varied substantially among regions of oursampled range and appear linked to differences in genomicarchitectures among traits.

Modest amounts of multi-locus variationin breeding zone PEA frequencies was associated with strongphenotypic differences and climatic gradients for both natural andselectively bred seedlings, reinforcing the need for assisted geneflow to mitigate climatic maladaptation.

Selectively bred seedlingshad stronger phenotype-genotype relationships than natural seedlingsamong breeding zones for three of four traits, and for all theclimate-genotype relationships, even though these differences werenot statistically significant.

Relationships among genotypes,phenotypes and climate were maintained or strengthened among theselective breeding programs we sampled, suggesting that amongbreeding zones the same assisted gene flow prescriptions are validfor both natural and selectively bred seedlings.

Even so, thepotential for trade-offs among traits due to substantial antagonisticpleiotropy was evident and should be carefully monitored as apotential source of climatic maladaptation in selectively bredseedlings.

Our use of PEA frequencies demonstrated a simple,sensitive and effective method of summarizing genomic data forpolygenic traits and detecting the effects of selective breeding onclimatically adaptive genotypes that are relevant to breedingstrategies and assisted gene flow policies.