Montazeaud G., Violle C., Fréville H., Luquet D., Ahmadi N., Courtois B., Bouhaba I., Fort F.
- Genotypic mixtures have been receiving a growing interest as genetic diversity could increase crop productivity. Resource-use complementarity is an expected key underlying mechanism, provided that varieties in the mixture differ in resource-related traits, notably root traits. We aimed at examining how trait differences and resource-use complementarity drive biomass production of genotypic mixtures.
- Four rice (Oryza sativa) genotypes including two Near-Isogenic Lines only differing in root depth were grown in monoculture and in two-way mixtures in pots under two levels of phosphorus supply. We analyzed the relative difference between mixture biomass and the best monoculture biomass in relation to between-genotype phenotypic distance on ten resource-related traits.
- Mixtures never outperformed the best monoculture. However, relative mixture productivity increased with increasing between-genotype distance in biovolume, specific leaf area and top soil root biomass. This was mainly driven by a “selection effect”: trait differences led to competitive ability differences and the dominant genotypes tended to gain more in mixture than the subdominant genotypes lost compared to monoculture.
- Rather than trying to minimize competition through resource-use complementarity, we argue that promoting interactions between genotypes that have different competitive abilities may be a more promising approach to design productive crop mixtures.