Domestication reduces phenotypic plasticity in chaya ( Cnidoscolus aconitifolius (Mill.) I.M. Johnst)

Abstract

Background: Natural selection optimizes phenotypic plasticity in plants found in environmentally variable habitats. However, it is unclear how artificial selection has affected the phenotypic plasticity of crops. Reduced plasticity in crop yield is often considered a desirable feature in cultivated plants; however, limited phenotypic plasticity in this and other traits may also affect the ability of crops to cope with environmental variation.
 Study species: Wild and domesticated chaya ( Cnidoscolus aconitifolius (Mill.) I.M. Johnst).
 Question: How domestication has affected the phenotypic plasticity of vegetative traits in response to the light environment?
 Methods: Leaf area, leaf perimeter, leaf specific area, leaf production, trichome density, stem elongation, growth in stem diameter and slenderness were measured in clones of wild and domesticated plants. These clones were allocated to two contrasting light treatments: fully exposed to sun vs . placement beneath a shade cloth. The phenotypic traits and reaction norms were compared between the genotypes of wild and domesticated plants.
 Results: Lower plasticity in leaf production and slenderness was observed in the domesticated compared to the wild plants. Leaf production and slenderness are associated with the shade avoidance syndrome, which was evident in wild plants but not manifested in domesticated plants. Reduced plasticity in leaf production also suggests yield stability.
 Conclusion: Artificial selection reduces phenotypic plasticity in the yield of chaya and in its response to variation in light availability.