Effects of Physical Parameters on Growth of Alternaria alternata causing Alternaria Leaf Spot of Lehsua

Lehsua (Cordia myxa Roxb.) also known as Lasoda, Gunda and Indian cherry, is a major fruit of the family Boraginaceae and grown in Rajasthan and other states of India. Alternaria leaf spot of lehsua, caused by Alternaria alternata is an important disease of this crop and day by day it is becoming severe in Rajasthan. The physiological study i.e. effect of temperature, RH, pH and effect of media on fungus (Alternaria alternata) was studied in vitro. The mycelial growth of Alternaria alternata was studied at different levels of temperature ranging from 15 oC to 35 oC. Maximum mycelial growth (87.51 mm) was recorded at 25 oC, while minimum (55.73 mm) was recorded at 15 oC. Maximum (88.71 mm) and minimum (49.00 mm) growth was recorded at 100 and 60 per cent level of RH, respectively; similarly maximum mycelial dry weight (847 mg) was recorded at pH 6.5 and minimum (300 mg) was at pH 8.0. The best growth supportive medium (87.88 mm dia. cololny) for the pathogen was potato dextrose agar medium followed by Czapeck’s Dox agar medium