To report on mechanisms of weed suppression in early vigour and weed suppressive wheat genotypes.

• In year 1 of this experiment, we demonstrated that genetically diverse wheat cultivars performed differently in two locations with varying rainfall patterns. Significant differences in crop biomass, LAI, weed count and biomass between  cultivars was also location dependent. These results show that although weed suppression in wheat is influenced by genotype, the genotypic response in wheat is clearly influenced by environmental factors as well, when it comes to growth, yield and weed suppression. However, certain cultivars were excellent performers in both locations in terms of weed suppression and crop yields and these included Espada and Condo and to a lesser extent Janz. Additional results will be obtained from metabolomic analyses to evaluate both primary and secondary biosynthetic pathways operational in crop genotypes and to determine if these pathways influence weed suppression in either location over time. The role of hydroxamic acids in weed suppression will be further examined in detail through targeted metabolic profiling in both soils and plant tissue. Additional field experiments will be repeated over the next 3 years to determine impacts of year and location upon wheat cultivar performance and weed suppression.