Garlic cloves (Allium sativum L.) conditioned at low temperatures and planting dates enhance the polyphenolic content of garlic cataphylls

Abstract

Temperature is regarded as one of the most important abiotic factors for plant growth and development. Low-temperature conditioning of garlic seed cloves (2 °C) for different periods (0, 15, 30, 45, and 60 days) before planting, and temperature as thermal time in accumulated growing degree days during plant growing from three planting dates were assessed. The experiment was conducted in a randomized complete block design with three replicates. The experimental units comprised six rows of 4 m long each. The main effect of planting date did not affect the total phenols and anthocyanin concentrations. On the contrary, these compounds were significantly affected by the main effect of cold conditioning of garlic cloves. The total phenols and anthocyanin concentrations increased significantly when garlic seed cloves were conditioned at low temperatures for 60 days. Total flavonoid concentration was modified by the interaction between the factors of low-temperature conditioning and planting dates. The best interaction was found when garlic cloves were conditioned with 720 chilling units before planting, and a crop cycle of 1130 growing degree days. As this report involves temperature, in terms of chilling units and growing degree days, the total phenols, flavonoids, and anthocyanins were linearly correlated with the growing degree days (negatively) and chilling units (positively). Further studies are needed on the content of these active biocompounds because there is a huge market for purple and spice garlic cultivars like ‘Calerense’.