Abstarct: Root rot and Vine decline disease of melon plants induced by Monosporascus cannonballus. secreted mextabolites (bottom and top of 10 kDa) of M. cannonballus were extracted from liquid culture media (Czapeck’s) of the fungus and purified using high voltage paper electrophoresis and sodium dodecyl sulphate-polyacrylamide gel electrophoresis, identified sequence of the bands with relative molecular mass of bigger than 10 kDa (26, 27, and 57) were determined via mass spectrometry. The smaller bands had the same sequence information and similar to serine protease from Lecanicillium psalliotae are most likely the isozymes of the same protein. Meanwhile, the 57 kDa band was identified as α-1,2-mannosidase similar to Phytophthora infestans (T30-4). Fungal serine proteases hydrolyze plant cuticule, while the mechanism of α-1,2-mannosidase has been remained elusive in pathogenisity. mextabolites under 10 kDa reacted positive with ninhydrin in electrophotogram. Due to the relative mobility on paper (Rm = 1) and biological activity such as water-soaking, it seems that this compound belongs to marasmines (a group of phytotoxic). Both small and big fractions demonstrated to be phytotoxic to melon leaves. This is the first report of phytotoxic compounds isolated from M. cannonballus contributing to disease induction in melon plants. In order to obtain tolerant melon lines via somaclonal variation, the explants were grown in MS medium with different concentrations of BA and 2,4-D hormones and different concentrations of fungal secretome for 7 weeks. The results were indicative of producing tolerant lines to M. cannonballus in the availability of 0.7 mg of the secretome.