الفهرس 
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Abstract
This study was carried out at Plant Pathology Laboratory and the farm of
Genetic Engineering and Biotechnology Research Institute (GEBRI), Menoufiya
University, Menoufiya Governate, Sadat city.
Tomato plants are the one of most important vegetable crops in Egypt and other
countries. Sclerotium rolfsii is the most destructive disease of tomato. Sclerotium
rolfsii Sacc. (Athelia rolfsii (Curzi) Tu &Kimbrough) causes the disease known as
southern blight in a wide variety of crops. Sclerotium rolfsii forms brownish
sclerotia that can survive in soil for long periods, Compost products have been
viewed as potential substitutes for fungicides; several independent studies
demonstrated that composts could reduce the incidence of plant diseases.
Hence, detailed studies on different types of compost including their microbial
communities and effect of some amendments like chitin, humic acid and effective
microorganisms (Lactic acid bacteria) on microbial communities to get qualified
compost have the ability to suppress Sclerotium blight in tomato plant and enhance
the growth of tomato.
Studies on compost revealed that Animal manure are not adequate for composting
and could limit efficiency of process due to high N concentration for organic-C and
lower C/N ratio. On the contrary, the microbial activity increased in spent agroresidues
obtained after cultivation of edible mushroom (Pleurotus) due to the
composition of cellulose, hemicellulose, lignin, carbon and nitrogen these agroresidues
which make proper C/N ratio. Also the addition of lignocellulosic
agricultural and forestry by-product in composting of nitrogen-rich wastes such as
animal manure gave proper carbon level and C/N ratio and the environment will be
conducive to growth of microorganisms.
The effect of humic substance, isolated from a composting substrate, was
evaluated on the mycelial growth of two strains of Sclerotium rolfsii and the
antagonistic Trichoderma sp. two strains of S. rolfsii treated with humic
substances, one strain isolated from tomato stems and the other isolated from the
roots of sugar beet. In general, any HS treatment significantly reduced the radial
growth of the S. rolfsii mycelium in normal potato dextrose agar (PDA) medium
enriched with humic acid compared to potato dextrose agar medium free from
humic acid. However S. rolfsii which isolated from tomato stems showed
resistance against the effect of humic acid after 4 and 9 days from inoculation due
to the soil treatment many times with humic acid. Humic acid treatment was also
able to alter the sclerotial production either by significantly reducing the number of
viable germinating sclerotia or by almost increasing the number of sclerotia to
double as a resistance mechanism towards the survival of S. rolfsii. Apparently, the
extent of the inhibitory action was related to some chemical and functional
properties of HS, such as the COOH group content and elemental composition. On
the contrary the same HS treatment generally did not inhibit the growth of
Trichoderma sp. This study showed no significant correlation between HS
chemical properties and Trichoderma sp. However, it showed the inhibitory effect
of Trichoderma sp. in presence of humic acid on two isolates of S. rolfsii with
percentage of inhibitions 53.3 % and 94.4%.