الفهرس 
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Abstract
The pathogen, Sclerotium rolfsii causes roots rots disease in several crops like carrot and red beet that decreases yield. In vitro and greenhouse experiments confirmed that inducers in combination with antioxidants, salts, chitosan and heat treatment decreased about 80 % of the rot. Treatments have no phytotoxic effect on carrots or red beets seedlings at low concentrations were effective as physical control agents against S.rolfsii. The aim of this study An attempt to find safe and healthy non-chemical methods to decreased this white rot disease that affects many crops caused by S.rolfsii, especially the roots of vegetable plants such as carrot and red beet. This fungal pathogenh as high ability to destroy crops and also in containers which transported by land and sea after harvest, it also affects exported vegetables and lowering their quality. The most important methods used in this study were using different temperatures to decrease the activity of the fungus, because the fungus may fail to produceits sclerotia and/or to cause its pathogenicity. Some organic acid were used to increase resistance to this pathogen, all these measures were used as a kind of non –traditional methods to resist this pathogen. 89 In vitro trials: The pathogen which causes the white-rot in plants was isolated from roots of the carrot and red beetroots naturally infested in Egypt.The effect of various temperatures on radial growth inhibition of S. rolfsii and formation of sclerotia was compared with the control. The results showed a slight difference between S.rolfsiii solates at different temperatures and radial growth in control. The differences were recorded asthe shape of the growth in Petri dishes as well as the number of sclerotia formed.The effect of various temperatures on sclerotia germination of S. rolfsii was studied for different periods under different temperatures used (20ºC, 40ºC, 70ºC ,and 100ºC)while time of exposure was 10 min, 20 min and 30 min. Results showed that the almost lethal temperature was 100ºC, whichgave 50%inhibitionin for sclerotia germination. There was no effect when sclerotia were exposed to 40ºC and 20ºC giving 0% inhibition, compared control.The effect of hexadienoic acid potassium salt, citric acid,and copper sulfate onS. rolfsiiradial growth and sclerotia number were measured at different concentrations i.e.0.0005M, 0.001M, and 0.005Minside Petri dishes contained the potato dextrose agar kept in an incubator at temperatures of 22 ° C for 7 days. HAPS was the most efficient atall concentrations since radial growth was 100% and sclerotia number was zero. For citric acid, there was no effect at the low and high concentrations giving 0% inhibition. Copper sulphateat high concentrations was weak allowed S.rolfsii to grow like the control where almost no difference was noticed between them. The effect of some antioxidants(ascorbic acid, Cinnamic acid, and menthol)on S. rolfsii radial growth and sclerotia number was tested at different concentrations 0.01M, 0.03M, and 0.05M in Petri dishes contained potato dextrose agar mediumand incubated at 22°C for 7 days. Cinnamic acid was the best treatment as the inhibition in radial growth was 100% and sclerotia number was zero. Menthol at high concentrations caused an inhibition in radial growth reach100%, while at low concentrations there was no effect on radial growth and sclerotia number. On the other side, A.A. had a slight affect at low concentrations, but at least was able to inhibit the growth of S. rolfsii by 67.5% inhibition at high concentrations. The effect of Chitosan on S. rolfsii radial growthand sclerotia numbers wastested by using different concentrations 300ppm 500ppm and 1000ppm. The results showed S. rolfsii inhibition in all concentrations of Chitosan. Fungal growth did not appear in high concentrations and the inhibition was 100%, however, at low concentration inhibition was 86.35%.Greenhouse experiment:• The effect of hexadienoic acid potassium salt, citric acid, and copper sulfate on the disease incidence and disease severity of southern blight of carrot roots caused by S. rolfsii was carried out with the same concentrations as mentioned before in soil infestedwith S.rolfsii sclerotia adapted for a week. Seeds of carrot and red beet were soaked after surface disinfection with 1chlorine. Results showed inhibition of the pathogen inpotassium treatment in its high and low concentrations as well, while copper was able to inhibit the fungus in its high concentrations. Only, citric acid had a weak effect in inhibiting the pathogenic fungus.The effect of some antioxidants(ascorbic acid, cinnamic acid, and menthol)on the disease incidence and disease severity of southern blight of red beetroots causedbyS. rolfsiiwas carried out with the same concentrations as mentioned in soil infested with sclerotia of S.rolfsii which adapted for a week while soaking Seeds of carrot and red beet were soaked after surface disinfection with chlorine. Results showed inhibition of the pathogen in Cinnamic acid treatment in its high and low concentrations as well, while menthol was able to inhibit the fungus in its high concentrations only, and the ascorbic acid had a weak effect at high concentration in inhibiting the pathogenic fungus.The effect of chitosan concentrations on the disease incidence and disease severity of southern blight of carrots roots causedbyS. rolfsiiwas carried out with the same concentrations as mentioned before, in soil infested with S. rolfsii sclerotia adapted for a week. Seeds of carrot and red were soaked in chitosan solutions beet after surface disinfection with chlorine. Results showed inhibition of the pathogen in high concentration treatments while; chitosan was able to inhibit the fungus in its low concentration after two months of the experimen.