Cellulose decomposing fungi and cellulase activity as affected by amistar and moncut fungicides

Abstract

Spray application of the two fungicides; Amistar (25% Azoxystrobin) and Moncut (25% Flutolanil) on faba bean plants in the field exhibited an inhibitive effect on the total and individual counts of cellulose decomposing fungi associated with roots and shoots of plants. The inhibitive effect of these fungicides depended mainly on the fungicide concentration. The inhibitive effect was increased with the increase in fungicide concentration at different periods of treatment. Forty four fungal isolates representing 35 species and 2 varieties belonging to 19 genera were screened for their abilities to produce exo-β-1,4 glucanase and endo-β-1,4 glucanase enzymes. All fungal isolates tested had the ability to produce cellulase enzymes, but with variable degrees. For exo-β-1, 4 glucanase, six isolates (represent 13.7% of total isolates) showed high cellulase activity. However, twenty one isolates (47.7% of total isolates) were found to be moderate in their cellulase activity. The remaining isolates (17 isolates, represent 38.6% of total isolates) were low producers of cellulase. For endo-β-1, 4 glucanase enzyme, five isolates (represent 11.4% of total isolates) showed high cellulase activity and twenty one isolates (47.7% of total isolates) had moderate ability to produce cellulase. The remaining isolates (18 isolates, represent 40.9% of total isolates) were low producers of cellulase. When these fungicides (at 100-800 ppm) were incorporated individually into the liquid culture medium specified for growth and an extracellular cellulase production was exerted an inhibitive effect on both mycelial growth and cellulase production of Aspergillus flavus var. columnaris, A. fumigatus, A. ochraceous, Mucor hiemalis and Trichoderma harzianum. Key words: Fungicides, faba bean, cellulose decomposing fungi, cellulase enzymes.