STUDY ON SCLEROTINIA SCLEROTIORUM (LIB.) DE BARY, THE CAUSAL OF WHITE ROT DISEASE IN GREEN BEANS AND ITS CONTROL UNDER LABORATORY CONDITIONS

Sclerotinia white rot of bean, caused by Sclerotinia sclerotiorum, is a major disease in green beans in Egypt, mainly in  ismailia region. It affects on the quantity and quality of the exportable yield. The purpose of this study is to quantify the effects of some factors affecting on growth of  S. sclerotiorum under laboratory conditions i.e. culture media, pH, Relative humidity (RH), light hours, carbon, nitrogen source and C/N ratios. Also, we did some attempts to control the fungus in vitro such by means of antagonists (17 fungal antagonist) and also bacterial antagonists (3 bacteria). Results showed that the  best solid medium was Potato dextrose agar (PDA) and the lowest suitable medium was the Yeast extract agar with average of 51.50 and 30.00 mm., respectively. While, Oatmeal extract was the best liquid medium giving 2.39 mycelial dry weight/m, while Leonian medium was not suitable for growth giving 1.21 mycelial dry weight/ml, respectively. The optimal pH was affected by  both 5.0 and 5.5 with 2.40 and 2.41 mycelial dry weight/ml, respectively. At RH, the optimal RH was 100% which gave 90 mm mycelial growth. Under C, N and C/N ratio, it was noticed that D-glucose was the best carbon source, while L-alanin was the best N source and both 9:1 and 20:1 were the best C/N ratio for growth. Under control studies, among all tested fungal antagonists, we noticed that Coniothyrium. minitans and Trichoderma. hamatum were the best antagonistic fungi in growth inhibition and sclerotial damage with 91.11, 85.83% and 95.8, 391.67%, respectively. Among all tested bacterial antagonists, it is noticed that Pseudomonas fluorescens and Streptomyces griseoviridis giving 61.94 and 59.72% inhibition in radial growth, while Bacillus subtilis   was the best bacteria in destroying the sclerotia with 70.83%.