Epidemiology and cultural characteristics of Penicillium digitatum causing green mould of citrus

摘要

Post harvest diseases account for 50% of losses in fruits stored under poor storage conditions especially under high humidity. They pose a major problem to the agriculture industry. Not only the quality and quantity are affected by the post harvest losses but loss in aesthetic appeal of the fruit and also result in consequent reduction in the market value. Post harvest losses in fruits can occur in terms of economics, quantity, quality and nutrition. The most common and serious diseases that affect citrus fruits were green moulds caused by Penicillium digitatum. The disease epidemiology and cultural characteristics of green mould of citrus was studied in 2015-2016 at Deptt. of Plant Pathology, AC&RI, Killikulum, T.N.A.U. The infected fruits were collected and used for isolation of pathogen. The six different isolates of Penicillium sp. obtained from infected fruits of different markets were screened to identify the most virulent strain. Three of them (isolate 1, 3 and 5) proved pathogenicity and one isolate (isolate 3) was highly virulent. Cultural characteristics of Penicillium digitatum. Were studied in four different solid and liquid media and also at eight different pH level and five different temperature level of the medium. Three replications were maintained for each treatment. The radial growth of the mycelium and mycelial dry weight was assessed for all the cultural characteristics. The results revealed that the maximum mycelial growth of Penicillium digitatum was found in CYA solid medium exhibiting 90.00 mm radial mycelial growth and 0.90g in CYA broth media. Among the different pH levels tested, Penicillium digitatum was found to grow well at pH 7.0 with mycelial growth of 90.00 mm for all the three isolates. Significantly the maximum mycelial growth of 90.00 mm was observed at temperature 25°C. It is thus concluded from this study that Penicillium digitatum can grow well in Czapek yeast agar (CYA) solid as well as liquid media at 7.0 pH and 25°C temperature.