Résumé
Increasing intra-specific diversity in agroecosystems is a promising practice, but belowground mechanismsshaping plant-plant interactions in mixtures remain unclear. We explored how belowground traits andassociated microbial communities influence durum wheat performance under limited resources, testingwhether traits in monogenotypic wheat stands could explain mixture performance. In a field experiment, 14durum wheat genotypes were cultivated alone or in pairs under two stress levels (control versus combinedwatering and N-fertilizer reduction). We measured root morphological traits, mycorrhizal colonization rate andmicrobial communities (mycorrhizal fungi, fungi, and bacteria) via Illumina metabarcoding on wheat roots andrhizospheric soil. Wheat performances were assessed by shoot biomass, N and P uptake. Mixed models wereused to assess which traits best explained wheat performances. In the stressed condition, mixtures exhibited11% higher shoot biomass compared to monogenotypic stands. Also only under stress, wheat performances(shoot biomass and P uptake) were significantly correlated to root biomass and colonization byMucoromycotina fungi, which are mycorrhizal fungi recently distinguished from the well-knownGlomeromycota. However, belowground traits and microbiome composition of monogenotypic stands failed toexplain mixture performances, pointing the need to explore different traits and integrate more diverse wheatgenotypes as 11 were modern cultivars. Although a definitive framework is lacking, our study offers promisingresults, urging further research in designing mixtures meeting farmers' needs