Document Type : Original Article
Author
Plant Pathology Research Institute, Agricultural Research Center, Giza, Egypt.
Abstract
The fungal plant pathogens were isolated from different host plants grown at different locations in Egypt. Alternaria alternata, Alternaria solani, Curvularia lunata, Fusarium solani, Fusarium oxysporum, Macrophomina phaseolina, Pyrenochaeta lycopersici, Rhizoctonia solani, Stemphylium botryosum, Trichoderma viride and Thielaviopsis basicola were recovered. Polygalacturonase (PG), chitinase (CH), cellulase (Cx) were determined using a suggested modified plate method with very low agar content (5gm/l). All fungal isolates produced remarkable activity of PG, CH and produced less cellulase (81.8% frequency) at 28°C. Six isolates (54.5%) were scored active PG producers namely T. viride, Th. basicola, F. oxysporum, P. lycopersici, M. phaseolina, S. botryosum, four isolates (36.4%) were moderate in this regard, R. solani (9.1%) was scored non producer at 21°C. Similar variation in Cx for the activity of three fungal isolates (27.3%) was recognized as active producers for T. viride, Th. basicola, F. oxysporum and three isolates (27.3%) were scored as moderate producers for P. lycopersici, F. solani, A. solani. on the other hand, five isolates, (45.5%) were found to be non-producers in this regard, A. alternata, R. solani, M. phaseolina, S. botryosum and C. lunata at 21°C. Moreover, two fungal isolates (18.2%) were highly active producers of chitinase (CH) activity for F. oxysporum and F. solani. Three isolates (27.3%) failed to produce chitinase (CH) under the conditions of the experiment for A. alternata, R. solani, M. phaseolina, though six isolates (54.5%) were found to be moderate chitinase (CH) producers by A. solani, C. lunata, P. lycopersici, S. botryosum, T. viride and T. basicola.Seven fungal isolates (63.6%) reacted positively at higher temperature (28°C) and higher production of (PG), (CH) and (Cx). The highest temperature tends to increase qualitatively the enzyme activity, while lower temperature decreased such effect.Four isolates, F. oxysporum, Th. basicola, T. viride, and P. lycopersici were scored active PG, CH and Cx at two different temperatures, 21 and 28°C, at four days incubation. It is worth noting that the semi solid agar medium (5 gm. agar/l) is being favorable for accurate detection of PG, Cx, and CH. Further trial with the modified semi-solid agar medium for evaluation of other enzymes involved in pathogenicity are needed.
Keywords
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