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چکیده
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The structure of nematode eggshell indicates that proteases and chitinases are necessary for infection by nematophagous fungi, and most of them produce these enzymes. Therefore the aim of this study was to assay chitinase activity in 34 isolates of various species of fungi obtained from golden potato cyst nematode (Globodera rostochiensis), as the most important potato pest, over two days of fungal growth (24 and 96 h). Chitinase specifc activity was determined by measuring the release of reducing saccharides from colloidal chitin by the N-acetylglucosamine-dinitrosalicylate method at 540 nm. Colorimetry based on image processing technique was used to discover colour changes in minimal synthetic medium for validation of chitinase activity. The 34 isolates were identifed based on morphological and molecular features including internal transcribed spacer (ITS) regions of ribosomal DNA. Results of the chitinase specifc activity measurement showed the chitinase specifc activity in all of them for 96 h was higher than for 24 h. Among isolates, the maximum and minimum chitinase specifc activity respectively belonged to isolate 154 (0.56 U mg-1) and isolate 6 (0.15 U mg-1) in 24 h, also isolate 113 (1.02 U mg-1) and isolate 6 (0.40 U mg-1) in 96 h. Colorimetric results confrmed that enzyme activity was associated with colour changes. The 34 fungal isolates were classifed in 11 genera most of which belonged to Fusarium. Finally, two isolates, 113 (Fusarium oxysporum) and 154 (Trichoderma atroviridae), with the highest chitinase enzyme activity are introduced as potent isolates to control the golden potato cyst nematode that can be used for chitinase enzyme production which is supposed to be used in commercial formulation.
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