Physiological and Nutritional Variability in Alternaria solani, Causing Early Blight of Tomato

Of the twelve culture media tested Potato dextrose agar supported best mycelial growth of A. solani (88.50 mm), followed by tomato leaf extract agar (84.22 mm), tomato fruit extract agar (82.52 mm), Richards agar (82.42 mm) and Czepek's dox agar (78.22 mm). The excellent (++++) sporulation was recorded by Potato dextrose agar, Oat meal agar, tomato leaf extract agar and Richards agar. The maximum mycelial growth and sporulation was recorded at temperature 25°C, followed by 30°C and 20°C. Maximum mycelial growth (88.58 mm) of the test fungus was recorded at pH 7.0, followed by pH 6.5 (78.44 mm) and 7.5 (76.52 mm). The excellent (++++) sporulation wasrecorded at pH of 7.00, 6.5 and 6.0. The best mycelial growth was recorded at alternate dark and light (88.72 mm), followed by continuous dark (82.34 mm). The excellent (++++) sporulation was recorded at continuous dark, followed by alternate dark and light (each 12 hrs duration). Among the eight carbon sources tested highest mycelial growth was recorded with starch (74.33 mm), followed by sucrose (58.88 mm) and maltose (56.78 mm); whereas, least mycelial growth was found with xylose (32.12 mm) and carbon control (22.28 mm). Carbon sources viz., sucrose, maltose and glucose recordedexcellent (++++) sporulation; whereas, xylose and control without carbon were without sporulation. Of the eight nitrogen sources tested, highest mean mycelial growth and excellent (++++) sporulation was recorded with Potassium nitrate (89.00 mm), followed by Magnesium nitrate (87.00 mm) and Sodium nitrate (86.40 mm). Least mycelial growth was found with Ammonium chloride (28.33 mm) and nitrogen control (38.42 mm).