Turnip

Brassica rapa

1. Identification and origin

The turnip (Brassica rapa L.) is a horticultural species of the Brassicaceae family, cultivated since Antiquity in Europe and Asia. It is believed to have been domesticated in the region of the Eastern Mediterranean and Western Asia, subsequently spreading throughout Europe. It includes several varietal groups used for the production of root, leaves or both.

2. Economic importance

The turnip is used for human consumption (roots and leaves), animal feed (green forage, silage and grazing) and as a cover crop in soil conservation systems. In Portugal, it is cultivated mainly on small and medium-sized farms, integrating horticultural rotations and traditional systems. At European level, it stands out for its rusticity, short cycle and low production cost.

3. Botanical characterisation

An annual or biennial herbaceous plant, with a globose or elongated tuberous root, white, yellow or purple in colour, depending on the cultivar. The leaves are lyrate or entire, forming a basal rosette. The floral stem appears in the second year, and may reach 60–120 cm. The flowers are yellow, typical of the Brassicaceae, gathered in clusters. The fruit is a silique containing several small and spherical seeds. There is great morphological variability between cultivars, both in the shape and colour of the root and in vegetative vigour.

4. Soil and climate requirements

The turnip adapts well to temperate climates, tolerating moderate cold and light frosts. It prefers temperatures between 10–20 °C. It develops better in loose, deep, well-drained soils rich in organic matter, with pH between 6.0 and 7.5. It is sensitive to waterlogging and compaction, which impair root development. It requires regular humidity, especially during the root thickening phase.

5. Main pests

• Cabbage root fly (Delia radicum): damage to the roots and reduction of vigour
• Flea beetles (Phyllotreta spp.): perforations in young leaves
• Aphids (Aphididae): sap sucking and transmission of viral diseases
• Noctuid caterpillars (Noctuidae): partial defoliation
• Root-knot nematodes (Meloidogyne spp.): root deformations

6. Main diseases

• Clubroot of crucifers (Plasmodiophora brassicae): root deformations and wilting
• Downy mildew (Hyaloperonospora parasitica): chlorotic spots and sporulation on the underside
• Powdery mildew (Erysiphe cruciferarum): white coating on the leaves
• Alternaria leaf spot (Alternaria brassicae): dark concentric spots
• Root rots associated with waterlogged soils

7. General crop management

Management includes the choice of cultivars adapted to the intended use (root or leaves), sowing at the appropriate time (autumn-winter or early spring), the use of certified seed and weed control in the initial phases. Fertilisation should be balanced, avoiding excesses of nitrogen that favour excessive vegetative development and susceptibility to diseases. Rotation with non-cruciferous crops is essential to prevent clubroot of crucifers and soil problems. Harvesting is carried out when the roots reach the desired size, avoiding delays that lead to lignification.

Bibliographic references

• EPPO Global Database – Brassica spp.
• CABI – Crop Protection Compendium – Brassica rapa
• Gómez‑Cortecero, A., et al. (2019). Biology and management of diseases in Brassica crops. In: Integrated Brassica Crop Production. Springer
• Rubatzky, V. E., & Yamaguchi, M. (2012). World Vegetables. Springer
• Dixon, G. R. (2007). Vegetable Brassicas and Related Crucifers. CABI Publishing