Effect of amendment of non-autoclaved and autoclaved natural soil, with Eucalyptus rostrata leaves, on fungal population and total content of phenolic compounds

الملخص EN

Inclusion of natural soil with Eucalyptus leaves and irrespective of amendment ratio, resulted in a significant general increase in the total soil fungal population due to the increase in soil organic matter.

However, individual effects of amendment on fungal genera revealed : a-significant increase in densities of Aspergillus, Penicillium, Paecilomyces, Fusarium, Alternaria, Cunninghamella, Cladosporium and Rhizopus spp., the majority of which are of a saprophytic nature.

b-slight fluctuation in population densities of less number of genera such as Trichoderma, Chaetomium and Humicola.

c-decrease in population densities of fewer number of genera as Cephalospdrium and Curvularia.

d-increase in population densities of Aspergillus fumigatus and Fusarium oxysporum, two of the tested fungi naturally present in the soil used, in spite of the significant increase in soil content of phenolics.

The growing of Aspergillus fumigatus, Fusarium oxysporum f.sp, lycopersici and Sclerotium cepivorum singly in sterilized soil free or included with Eucalyptus amendment showed that: a- the main source of increased phenolic content of soil was the plant tissue and not any of the fungi included.

b-F.

oxysporum significantly increased in density while counts of each of A.

fumigatus and S.

cepivorum dropped clearly from the first 2 weeks.

Such drop is most probably due to the inhibitory effect of phenolics derived from decayed Eucalyptus leaves, since the possibility of inhibition due to increased saprophytic antagonists was experimentally eliminated.