Unraveling diversity in wheat competitive ability traits can improve integrated weed management

AbstractWeed pressure can be high in organic and low-input farming and reduce yield and produce quality. In these systems, integrated weed management includes different agronomic practices but rarely focuses on the use of more competitive cultivars, which would reduce reliance on direct weed control methods and their detrimental effects on soil and the environment. We characterized 160 common wheat (Triticum aestivum L.) accessions cultivated in Italy since the nineteenth century for four traits linked to competitive ability against weeds (above-ground biomass before stem elongation, tillering index, plant height, and flag leaf morphology) and for two production-related traits (grain yield and thousand-kernel weight). This approach aimed to identify the most suitable combinations of competitiveness and production traits, which often show trade-offs, and led to the identification of eight accessions with reduced grain yield to plant height trade-off. We genotyped the collection with SNP markers, revealing high molecular diversity and highlighting a trend of polymorphism loss passing from heritage to modern germplasm, with the presence of unique polymorphisms in both groups. These results underline the importance of studying both heritage and elite germplasm when focusing on traits that are not targeted by formal breeding, such as the competitive ability against weeds. Marker-trait associations (MTAs) with false discovery rates (FDR) < 5% were detected for all traits studied, while MTAs with FDR < 1% were detected for plant height, biomass, grain yield, and thousand-kernel weight. We identified MTAs confirming associations already reported in the literature as well as MTAs pinpointing new genomic regions that may disclose new breeding perspectives in common wheat. This study, for the first time, shows the high potential of interdisciplinary research bridging advanced genetic studies with agroecological approaches for selecting more competitive common wheat germplasm as additional tool in more sustainable integrated weed management systems