Lupin

Lupinus spp.

1. Identification and origin

Lupins (Lupinus spp.) are herbaceous legumes of the Fabaceae family, distributed mainly across the Mediterranean basin, North America and South America. In Portugal, the most notable are Lupinus albus L. (white lupin), Lupinus luteus L. (yellow lupin) and Lupinus angustifolius L. (blue lupin). They are used as forage crops, green manures and, in the case of L. albus, also for human consumption after suitable processing to remove alkaloids.

2. Economic importance

Lupins are of high agronomic importance owing to their capacity for biological nitrogen fixation, contributing to soil fertility and to a reduction in mineral fertilisation. They are used in pastures, grain production for animal feed and structural improvement of the soil. L. albus additionally has food and industrial value. The Mediterranean species are relevant in dryland systems, thanks to their good tolerance of drought and poor soils.

3. Botanical characterisation

Lupinus spp. plants are annual or perennial, with a habit varying between 30 and 150 cm. The leaves are compound, palmate, with 5–11 leaflets. The inflorescences are dense racemes, with papilionaceous flowers of variable colour (white, yellow, blue or purple). The pods are elongated, containing protein-rich seeds. The root system is deep and vigorous, with symbiotic nodules of Bradyrhizobium spp.

4. Soil and climate requirements

Lupins adapt well to Mediterranean climates, tolerating summer drought and moderately low temperatures. They prefer acidic to slightly acidic soils (pH 5.0–6.5), well drained and low in active limestone. They are sensitive to waterlogging and salinity. Productivity is favoured by adequate autumn–winter rainfall and mild temperatures during the vegetative cycle.

5. Main pests

• Weevils (Sitona spp.) — root damage and reduction of nitrogen fixation
• Aphids (Aphis craccivora, Acyrthosiphon pisum) — sap sucking and transmission of viruses
• Caterpillars (Spodoptera spp., Helicoverpa armigera) — reduction of aerial biomass
• Thrips (Frankliniella occidentalis) — damage to young leaves and flowers
• Nematodes (Ditylenchus dipsaci) — deformations and necroses in vegetative tissues

6. Main diseases

• Anthracnose (Colletotrichum lupini) — necroses, lesions on the stems and death of young plants
• Root rots (Rhizoctonia solani, Pythium spp.) — establishment failures
• Powdery mildew (Erysiphe spp.) — white coating and reduction of photosynthesis
• Rust (Uromyces lupinicolus) — leaf pustules and loss of vigour
• Lupin mosaic virus (LCMV) — mosaics and reduction of productivity

7. General crop management

Lupin management is based on selecting the species and cultivar suited to the soil type and water regime. Inoculation with appropriate strains of Bradyrhizobium spp. is essential to maximise nitrogen fixation. Crop rotation reduces the pressure of soilborne diseases. Weed control is critical in the early stages owing to the relatively slow growth. Harvesting for grain should occur when the pods are dry and the seeds reach physiological maturity.

Bibliographic references

• EPPO Global Database – Lupinus spp.
• CABI – Crop Protection Compendium – Lupinus spp.
• Gladstones, J. S. (1998). Lupins as Crop Plants: Biology, Production and Utilization. CAB International.
• Lucas, M. M. et al. (2015). The future of lupin as a protein crop in Europe. Frontiers in Plant Science, 6, 705.
• Dracup, M., & Thomson, B. (2000). Lupin improvement in Australia. Australian Journal of Agricultural Research, 51, 813–823.