Rapeseed

Brassica napus

1. Identification and origin

Rapeseed (Brassica napus L.) is an annual plant of the Brassicaceae family, resulting from natural hybridisation between Brassica rapa L. and Brassica oleracea L. It is native to Europe and Western Asia, and is currently one of the main oilseed crops grown in the world, especially in temperate climates.

2. Economic importance

Rapeseed is grown mainly for the production of food and industrial oil, including biodiesel. The meal resulting from oil extraction is used as a protein source in animal feed. Modern “double zero” rapeseed varieties (low in erucic acid and glucosinolates) have significantly increased the food and commercial value of the crop. It is also important in crop rotations, contributing to soil structuring and the reduction of cereal pests.

3. Botanical characterisation

An annual plant of erect habit, 1–1.5 m tall. The leaves are alternate, glaucous, with an entire or lobed blade. The flowers are yellow, typical of the Brassicaceae, gathered in racemes. The fruits are elongated siliques containing numerous spherical seeds, rich in oil. The root system is taprooted, with a good capacity to explore the soil.

4. Soil and climate requirements

It prefers cool temperate climates and is grown as an autumn-winter crop in many regions. It develops best in deep, fertile, well-drained soils, with a pH between 6.0 and 7.5. It is sensitive to waterlogging and benefits from a good water supply during flowering and seed filling. It tolerates moderate frosts after establishment.

5. Main pests

• Cabbage seed weevil (Ceutorhynchus assimilis): damage to the siliques and seed loss.
• Flea beetle (Phyllotreta spp.): leaf punctures in seedlings.
• Cabbage root fly (Delia radicum): root damage and reduced vigour.
• Aphids (Aphididae): sap sucking and transmission of viruses.
• Lepidopteran caterpillars (Plutella xylostella, Pieris spp.): defoliation and reduced productivity.

6. Main diseases

• Clubroot of crucifers (Plasmodiophora brassicae): root deformations and decline.
• Alternaria blight (Alternaria brassicae, A. brassicicola): leaf spots and seed losses.
• Downy mildew (Hyaloperonospora brassicae): chlorotic spots and necrosis.
• White rot (Sclerotinia sclerotiorum): wilting and crown rot.
• Stem canker (Leptosphaeria maculans): necrosis and lodging of stems.

7. General crop management

Management includes choosing adapted varieties, sowing at the appropriate time, balanced density and adjusted fertilisation, especially with nitrogen and sulphur. Crop rotation is essential to reduce the pressure of soil-borne diseases, especially Plasmodiophora brassicae. Monitoring of flea beetles, weevil and aphids is critical in the early stages. Harvesting should be carried out when the siliques reach physiological maturity, avoiding losses through dehiscence.

Bibliographic references

• EPPO Global Database – Brassica napus.
• CABI Crop Compendium – Brassica napus.
• Kimber, D., & McGregor, D. I. (1995). Brassica Oilseeds: Production and Utilization. CAB International.
• Rimmer, S. R. et al. (2007). Compendium of Brassica Diseases. APS Press.
• Friedt, W. et al. (2018). Oilseed rape breeding. Springer.