Abstract Egyptian broomrape (Orobanche aegyptiaca) is a major root parasite of tomato plant (Solanum lycopersicum) with devastating effects on crop yield. There is no certain strategy for complete control of O. aegyptiaca in tomato farm. Developing a reliable control method depends to large extent on understanding molecular events happening during host-parasite interaction. A proteomic-based study was carried out to elucidate molecular mechanisms responsible for resistance of tomato seedlings to O. aegyptiaca at early stages of infection. For this purpose, the changes in protein profiles of two resistant genotypes of wild tomato (Solanum chilense TL00798 and S. pimpinellifolium L00134) and a sensitive genotype (S. lycopersicum Var. Early Orbana 111) were compared seven days after infection with O. aegyptiaca using two-dimensional gel electrophoresis. Out of 550 spots visualized by this approach, 22 proteins were differentially expressed among the genotypes (P≤0.01) with at least 2 folds increase or decrease in expression and were further studied by MALDI-TOFTOF mass spectrometry technique. As a result, 14 proteins involving in various cellular mechanisms such as signal transduction pathway, regulation of gene expression, stress resistance, programmed cell death and energy metabolism were identified. Accordingly we can say that the majority of identified protein spots were related to defence and stress responses. Expression pattern of the identified proteins implies involvement of defence mechanisms at early stage of O. aegyptiaca infection.

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