Evolutionary adaptation in cow cockle Vaccaria hispanica: a potential alternative crop

Abstract

Domestication is the process by which a wild plant evolves into a cultivated plant by undergoing morphological, physiological or molecular changes. These changes may be due to conscious selection (primary cultivated plant) or unconscious selection (secondary cultivated plant) by man. These evolutionary changes need to be studied to understand the transition from wild to cultivated plant. Cow cockle (Vaccaria hispanica) is a summer annual species introduced to North America from Europe. It is being considered for commercial production because of its seed constituents. The purpose of this study is to determine which cow cockle populations are best adapted to cultivation and the plant characteristics that are responsible for such adaptation. We compared 15 cultivated and wild cow cockle populations from different parts of the world for 12 agronomic and morphological traits. Multivariate analyses were performed to group populations according to their agronomic and morphological similarity. Cluster analysis revealed three main population groups among the 15 accessions based on the traits studied. Two linear discriminants were obtained by discriminant function analysis accounting for 96 % of the variability among the populations. Analysis of variance showed significant (P < 0.001) differences for most of the characters studied; however populations did not differ for emergence and disease resistance. Physiological maturity, seed size, plant height, flower size and seed yield were responsible for the divergence in cow cockle populations. The cluster including the cultivars Pink Beauty, Turkey, PB-87, Scott and UMan-89 were characterized by taller plants (~58 cm), production of large seeds (~7.7 g) and high seed yield (~2,400 kg ha−1). A high agronomic potential in these populations may be due to pre-adaptation towards domestication, which they might have acquired through the convergent adaptation to large-seeded crops. Although some populations showed adaptation to cultivation, characters relating to their seed dispersal may need further selection, and can be viewed as variants that are prepared for initial stage of domestication.