Phytochemical analysis and antifungal efficiency of Origanum majorana extracts against some phytopathogenic fungi causing tomato damping-off diseases

Abstract

Plant diseases represent one of the major problems causing yield loss of tomato crops, especially root rot and seedling damping-off diseases caused by some phytopathogenic fungi like Fusarium solani (Fs), F. oxysporum (Fo), and Macrophomina phaseolina (Mp) frequently detected in tomato either alone or in combination infection. The objective of the present study is to assess the antifungal activity of Origanum majorana extracts against the phytopathogenic fungi, Fs, Fo, and Mp, thereby avoiding controlling the disease with chemical fungicides. In this context, the acetonic extracts of O. majorana exhibited the highest antifungal activity against the tested phytopathogens. However, F. solani exhibited high resistance to Ridomil fungicide at the tested concentrations. A chemical analysis of the O. majorana acetonic extract was conducted to determine the main phytoactive constituents exhibiting fungicidal activity. In this regard, gas chromatography and mass spectrometry confirmed that 4-terpineol was the main phytoactive compound followed by γ-terpinolene exhibiting relative percentages of 24.36 and 8.26%, respectively. These results proved that the marjoram extract may contribute to the development of an alternative and natural fungicide to protect tomato crops from damping off and root rot diseases, avoiding the usage of chemical fungicides.