Identifying genetic variation associated with environmental gradients
and drought-tolerance phenotypes in ponderosa pine
Abstract
As climate changes, understanding the genetic basis of local adaptation
in plants becomes an ever more pressing issue. Combining
Genotype-Environment Association (GEA) with Genotype-Phenotype
Association (GPA) analysis has an exciting potential to uncover the
genetic basis of environmental responses. We use these approaches to
identify genetic variants linked to local adaptation to drought in
Pinus ponderosa. Over 4 million SNPs were identified using 223
individuals from across the Sierra Nevada of California. We found 1458
associated with five largely uncorrelated climate variables, with the
largest number (1151) associated with April 1st snowpack. We also
conducted a greenhouse study with various drought-tolerance traits
measured in seedlings grown in control and drought treatments. 817 SNPs
were associated with control-condition trait values, while 1154 were
associated with responsiveness of these traits to drought. While no
individual SNPs were associated with both the environmental variables
and the measured traits, several annotated genes were associated with
both, particularly those involved in cell wall formation, biotic and
abiotic stress responses, and ubiquitination. However, the functions of
many of the associated genes have not yet been determined due to the
lack of gene annotation information for conifers. Future studies are
needed to assess the developmental roles and ecological significance of
these unknown genes.