Blumeria graminis f.sp. tritici (Bgt) is an obligate biotrophic fungal pathogen responsible for powdery mildew in bread wheat (Triticum aestivum L.). During the first steps of this pathogenic interaction, basal defense mechanisms take place in wheat leaves. We used RT-qPCR and metabolomic approaches to analyze these early stages of the interaction between Bgt and the moderately susceptible wheat cultivar Pakito. The expression of genes encoding pathogenesis-related (PR) proteins (PR1, PR4, PR5 and PR8), known to target the pathogen, increased during the first 48 hours post-inoculation. Moreover, RT-qPCR and metabolomic analyses pointed out the importance of the phenylpropanoid pathway in quantitative resistance against Bgt. Among metabolites of this pathway, hydroxycinnamic acid amides containing agmatine and putrescine as amine components accumulated from the second to the fourth day after inoculation. This suggests the involvement of these metabolites in quantitative resistance via cross-linking processes in cell wall for reinforcement, what is supported by the up-regulation of PAL (phenylalanine ammonia-lyase), PR15 (encoding an oxalate oxidase) and POX (peroxidase) further inoculation. This study increases knowledge on basal resistance in wheat, giving new targets to investigate induced resistance in wheat towards Bgt.