Contrasting performances of modern and landrace cultivars in wheat mixtures and wheat-legume intercrops in organic and low input conditions - Euphytica

The context of global ecological crisis has led to the rediscovery and reuse of landrace crop cultivars. Many recent studies testify the high-quality value of landraces, as well as their agronomic interest in terms of adaptability to pedoclimatic environments. The aim of this study was to highlight the differences between modern varieties and landraces for their mixing and intercropping capabilities. An on-farm experiment, in low input conditions, took place in five different sites in Western France (3 repetitions per site) during three seasons (from seedling 2014 to harvest 2017). Three landraces and three modern varieties were compared in three mixing modalities: monoculture, cultivar mixture and legume intercropping. This on-farm experiment with no chemical input has offered new insights on the differences between modern varieties and landraces: (1) Landraces yielded around 2.8 t ha−1 while modern varieties yielded around 3.0 t ha−1, a difference that was not significant. (2) Landraces’ yields were more stable over sites. (3) Wheat straw dry matter yields were 1.5 t ha−1 higher for landraces than for the modern ones. (4) The grain nitrogen content for landraces was 13.5% while it is 12.3% for modern varieties. (5) Landraces were healthier than modern varieties; (6) Arbuscular mycorrhiza fungi wheat root colonisation was 5% higher in landraces (35.2%) than modern varieties (29.4%) in these conditions unfavourable to mycorrhiza due to ploughing. (7) Wheat lodging was 38.5% for landraces while it was around 1% for modern varieties. Intercropping wheat with legumes decreased wheat grain yield by around 25%, but increased wheat grain nitrogen content from 12.7 to 13.8%, independently between landraces and modern varieties. This study provides novel evidence of the interests of diversifying crops, either through intra-varietal genetic diversity (the use of landraces) and inter-specific diversity (intercropping of wheat and legumes), for both wheat performance and stability.