Effect of domestication on phenotypic plasticity in chaya (Cnidoscolus aconitifolius (Mill) I.M. Johnstone)

Abstract

It is widely recognized that phenotypic plasticity may increase the survival of plants in environmentally variable habitats. However, the manner in which artificial selection affects the phenotypic plasticity of crops is poorly understood and there is no previous study in clonally propagated crops. The goal of this study was to assess the effect of domestication on phenotypic plasticity in leaf traits, growth rates and allocation patterns, under contrasting light environments, in the clonally propagated crop chaya (Cnidoscolus aconitifolious (Mill) I.M. Johnstone). Leaf area, leaf perimeter, leaf specific area, leaf production, trichome density, growth in height, growth in stem diameter and slenderness were measured in 97 clones belonging to 20 genotypes (10 wild and 10 domesticated). The clones were allocated to two contrasting light environments: fully exposed to sun vs. placement beneath a shade cloth. Reaction norms for each trait were compared between wild and domesticated clones. Results suggest that domestication and light environment had a non-additive effect on phenotypic plasticity in leaf production and slenderness. Reduced plasticity in these traits was observed in domesticated plants compared to that of their wild relatives. Leaf production and slenderness are associated with the shade avoidance syndrome, which is evident in wild plants but not manifested in domesticated plants. Reduced plasticity in leaf production also suggests yield stability, since the leaves form the edible part of chaya. I conclude that artificial selection reduces phenotypic plasticity in the yield of chaya and in its response to variation in the light environment.