In situ and in vitro suppressive effect of agricultural composts and their water extracts on some phytopathogenic fungi

In situ and in vitro experiments were carried out to determine the effect of various composts (leafy fruit compost (LFC), garden compost (GC), and crops compost (CC)) and their water extract on Pythium debaryanum, Fusarium oxysporum f.sp. lycopersici, Sclerotium bataticola. Compost water extract (CWE) of LFC, GC, and CC were found to contain Bacillus spp., Micrococcus spp., Staphylococcus spp. and Corynebacterium spp., and the fungi Aspergillus spp., Rhizopus spp., and Drechslera spp., and various Actinomycetes. In situ results indicated considerable decrease in fungal growth around the unautoclaved compost especially in the case of S. bataticola and F. oxysporum f.sp. lycopersici, compared to the autoclaved compost. In vitro tests showed that concentration of CWE at 5, 10 and 15% (v/v) suppressed the hyphal growth of S. bataticola by 83% using 5% CC and by 94.4% using 5% LFC or 10% GC, and F. oxysporum f.sp. lycopersici by 94.4% using either composts. CWE of GC decreased fungal dry weight of F. oxysporum f.sp. lycopersici by 97.7%, P. debaryanum by 92.8%, and S. bataticola by 84.4%; CC decreased F. oxysporum f.sp. lycopersici by 94%, P. debaryanum by 86.2%, and S. bataticola by 63.3%, while CWE of LFC was the least effective against the tested fungi. CWE produced clear inhibition zones against all the tested fungi. Microflora found in CWE have an important role in suppressing the growth of tested fungi. CWE contained neither antibiotics nor siderophores. The presence of protease, chitinase, lipase and -1,3 glucanase (lysogenic enzymes) in CWE indicates a possible role in fungal degradation.