Abstract: Spent wheat straw (after cultivation of oyster mushroom, Pleurotus floridanus) was infested into the soil at different concentrations (1, 2, 5% w/w) to study its effect on the growth of broad bean (Vicia faba) susceptible to Botrytis fabae. In addition, the effect of spraying the plant with its water extract was also studied. In seedling stage, the non infected broad bean plants treated with 1 and 2% spent straw (ss) showed an increase in shoot length and at 5% ss as well as upon spraying with water extract of spent straw (wess) root length increased. All treatments increased both root and shoot length in infected plants only, while the number of leaves was increased in both infected and non infected plants. The number of nodules and lateral roots, fresh and dry weight of both shoot and root increased at 2 and 5% ss. Moreover, spraying with wess increased fresh and dry weight of root in all plants. In non infected plants, treatment with wess and 2% ss increased glucose, sucrose and total carbohydrate in both root and shoot, in addition to increasing sucrose at 1%. On the other hand, glucose contents were significantly increased at 5% ss while all treatments increased sucrose in root and at 1% in shoot of infected plants. Also, increasing in polysaccharides in whole plants occurred at 2 and 5% as well as with wess. However, all treatments increased total carbohydrates in root of the infected plant. Total nitrogen was significantly increased only in infected plants when sprayed with wess and treated with 5% ss. In flowering stage, all treatments increased shoot length in non infected plants. However, 2 and 5% ss increased both root and shoot length of the infected plants. Increasing the number of rootlets and nodules in the non infected plants was recorded at 2% ss but, in infected ones an increase was apparent at 2 and 5% ss. Increase in fresh and dry weight of root was achieved at 1 and 2% ss in non infected plants, and at 2 and 5% ss in infected ones. Shoot fresh and dry weight increased at 2% in all plants. Glucose content of whole non infected plants was significantly increased at 1 and 2% ss. However, 5% ss and (wess) increased glucose content in both root and shoot respectively in the infected plant. Infestation with 1 and 2% ss and only 2% ss caused an increase in sucrose of root and shoot respectively in non infected plants. Additionally (wess) increased sucrose in both root and shoot. However, spraying the infected plant with (wess) or grow in soil supplemented with 2 and 5 or 5% only caused an increase in sucrose content in root and shoot respectively. Contents of polysaccharides increased in root of non infected plants and infected at 1 and 2% ss respectively while spraying with (wess) increased polysaccharides in the whole infected plants. Total carbohydrates content in non infected plant was significantly increased at 1 and 2% ss in root and shoot respectively, while in infected plants all treatments and only spraying with (wess) increased total carbohydrates of root and shoot respectively. On the other hand, total nitrogen of both root and shoot increased only at 5% ss as well as spraying with wess in infected plant.