الفهرس | Only 14 pages are availabe for public view |
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%. |