PATHOLOGICAL STUDIES ON CROWN AND STEM ROTS OF EGYPTIAN CLOVER

Abstract

Isolation trials from the rotted crowns and stems of Egyptian clover plants were carried out. The isolated fungi were purified and identified as Alternaria spp., Fusarium spp., F.solani, Macrophomina phaseolina, Pythium spp., Rhizoctonia solani, Sclerotinia sclerotiorum, S.trifoliorum, Trichoderma album, T.harzianum and T.viride. No apparent infection by crown and stem rot diseases was observed on clover plants during October, November and May then the infection began to appear from December to April of the next year. The highest infection by crown rot occures during January and by stem rot during February. Pathogenicity test by soil infestation and stem inoculation revealed that all the tested fungi were able to infect clover plants except Trichoderma spp. S. sclerotiorum infected all the plants that belong to family Fabaceae, i.e. alfaalfa, bean, chick pea, Egyptian clover, faba bean, etc…as well as lettuce, safflower cantaloupe, cucumber, and potato and failed to infect barley and wheat. All the tested Egyptian clover cultivars were susceptible to infection by crown and stem rots. In addition, Fahl cv. was the lowest susceptible one. Meanwhile, Miskawy cv. was the highest susceptible one. The cardinal degrees of temperature of S. sclerotiorum were5, 20 and 25°C. Also, the fungus failed to form any sclerotia at 0.0 and 5°C. All of the four tested fungicides caused significant reduction to the radial growth of the tested fungus compared with control treatment. Tachigaren was the most effective fungicide. Culture filtrates of the tested eight Bacillus spp. and the fourteen Trichoderma spp. isolates resulted in different degrees of reduction to the radial growth and the germinated sclerotia of S. sclerotiorum.The preceding crop resulted in significant reduction to the natural infection by crown and stem rot. In addition, planting rice before Egyptian clover caused great reduction in the natural infection by crown and stem rots. Adding organic manure, i.e. balady old manure, chicken manure, compost and peat moss before sowing Egyptian clover in soil infested with S. sclerotiorum resulted in significant reduction in the severity of crown and stem rots with significant increase in the weight of green forage yield compared to control treatment. Meanwhile, balady fresh manure resulted significant increase in the severity of crown and stem rots with significant decrease in the weight of green forage yield compared to control treatment. The tested bioagents, i.e. B. thuringiensis-1 and T. harzianum-3 as well as soil solarization resulted in significant reduction in the severity of clover crown and stem rots with significant increase in the green forage yield compared to control treatment. The use of calcium cyanamide, compost and soil solarization, each alone or in combinations, resulted significant reduction in the severity of clover crown and stem rots with significant increase in the green forage yield compared to control treatment. The use of leaves powder of lemon grass, solarization and Tachigaren each alone or in combinations, resulted significant reduction to crown and stem rots severity as well as significant increase in the produced green forage yield compared to control treatment. Key wards: Crown and stem rots, Egyptian clover, disease management, physiological studies, and Sclerotinia sclerotiorum