The infection process of pea roots with A. euteiches and P. pisi was evaluated by analysing gene expression of selected defence marker genes such as ACO (1-aminocyclopropane-1-carboxylate oxidase), Pi49 (PR10-like), ABA17 (abscisic acid responsive gene) and chit4 (chitinase 4), using reverse transcription quantitative PCR (RT-qPCR). The gene discussed is KLK15; the disease is infection.