Pathological and nutritional studies of Phomopsis citri causing fruit rot of Mandarin in Rajasthan

Fruit rot incited by Phomopsis citri of mandarin [(Citrus reticulata) was observed at Horticultural farm, Rajasthan College of Agriculture, Udaipur (Rajasthan). Natural rotted fruits had abundant black sporulation on sunken necrotic spot. Fungus was identified as Phomopsis citri. Pathogenicity test were confirmed on main host as well as on Kinnow, sweet orange, mosambii, karna khatta and lemon fruits. In vitro studies revealed that fungus grew and sporulated well on Potato dextrose agar as well as malt extract solid and liquid media. An optimum temperature of 30±2°C favoured maximum mycelial growth (82.0 mm) and sporulation (+++) followed by 25±2°C (68.0 mm). Out of Seven type of light intensity, brown light was found more favorable (90.80 mm) by supporting the growth and sporulation of the pathogen and darkness light gave least growth and sporulation. Relative humidity at 100 per cent gave maximum mycelial growth (88.90 mm), sporulation (+++) and spore germination (92.40 and 96.50 per cent at 6 and 12 hrs) followed by 80 per cent (74.40 mm, +++, 78.00 and 82.10 per cent) respectively. Least mycelial growth (8.20 mm), sporulation and spore germination was recorded at 20 per cent RH. Among thirteen different pH levels, the pH 6.5 was found to be more supported for dry mycelial weight (299.80 mg) and sporulation (+++) followed by 7.0 pH(289.90 mg) and least mycelial weight (208.40) was obtained at 4.0 pH.