Gradient of vernalization requirement in carrot cultivars from diverse geographical origins

Abstract

On the basis of their vernalization requirement (VR) for flowering, a genetically conditioned trait, carrots (Daucus carota L.) are typically classified as annuals and biennials. A previous study using F2 populations derived from crosses among carrots from different geographical origins revealed a model of two genes and three alleles controlling VR, with dominance of annuality for both genes. The present work evaluated VR in carrot cultivars from diverse origins, including those used in a previous study. We induced vernalization during different periods of cold exposure (20, 30, 40, 60, and 90 d) and different temperatures (∼5 and ∼15 °C). Increased flowering rates and earlier onset of flowering were associated with longer and more intense cold exposures. In most cultivars, 60–90 d at 5 °C (but not at 15 °C) were enough for vernalizing a large proportion of the plants. In general, biennials required longer cold exposure than annuals to flower, although variation within annuals and biennials was also found, suggesting a gradient of VR in the carrot germplasm, which reinforces our previously proposed genetic model. The plant materials used in this work cover the broadest range of VR in carrot reported to date. These findings contribute to carrot breeding and production, helping to choose the specific genotype and appropriate sowing time in different environments either for root or seed production.