Data from: Resource allocation trade-offs and the loss of chemical defences during apple domestication

Background and Aims: Most crops have been dramatically altered from their
wild ancestors with the primary goal of increasing harvestable yield. A
long-held hypothesis is that increased allocation to yield has reduced
plant investment in defence and resulted in crops that are highly
susceptible to pests. However, clear demonstrations of these trade-offs
have been elusive due to the many selective pressures that occur
concurrently during crop domestication. Methods: To provide a robust test
of whether increased allocation to yield can alter plant investment in
defence, this study examined fruit chemical defence traits and herbivore
resistance across 52 wild and 56 domesticated genotypes of apples that
vary >26-fold in fruit size. Ninety-six phenolic metabolites were
quantified in apple skin, pulp and seeds, and resistance to the codling
moth was assessed with a series of bioassays. Key Results: The results
show that wild apples have higher total phenolic concentrations and a
higher diversity of metabolites than domesticated apples in skin, pulp and
seeds. A negative phenotypic relationship between fruit size and phenolics
indicates that this pattern is driven in part by allocation-based
trade-offs between yield and defence. There were no clear differences in
codling moth performance between wild and domesticated apples and no
overall effects of total phenolic concentration on codling moth
performance, but the results did show that codling moth resistance was
increased in apples with higher phenolic diversity. The concentrations of
a few individual compounds (primarily flavan-3-ols) also correlated with
increased resistance, primarily driven by a reduction in pupal mass of
female moths. Conclusions: The negative phenotypic relationship between
fruit size and phenolic content, observed across a large number of wild
and domesticated genotypes, supports the hypothesis of yield–defence
trade-offs in crops. However, the limited effects of phenolics on codling
moth highlight the complexity of consequences that domestication has for
plant–herbivore interactions. Continued studies of crop domestication can
further our understanding of the multiple trade-offs involved in plant
defence, while simultaneously leading to novel discoveries that can
improve the sustainability of crop production.