  Understanding the relationship between genomic variation and variation in
phenotypes for quantitative traits such as physiology, yield, fitness or
behavior, will provide important insights for both predicting adaptive
evolution and for breeding schemes. A particular question is whether the
genetic variation that influences quantitative phenotypes is typically the
result of one or two mutations of large effect, or multiple mutations of small
effect. In this paper we explore this issue using the wild model legume
Medicago truncatula. We show that phenotypes, such as quantitative disease
resistance, can be well-predicted using genome-wide patterns of admixture, from
which it follows that there must be many mutations of small effect. Our
findings prove the potential of our novel 'whole-genome modeling' -WhoGEM-
method and experimentally validate, for the first time, the infinitesimal model
as a mechanism for adaptation of quantitative phenotypes in plants. This
insight can accelerate breeding and biomedicine research programs.
