P.K. Chohan’s scientific contributions

Alternaria fruit rot caused by Alternaria alternata was observed on fruits of brinjal (Solanum melongena L.) as dark brown-black concentric rings. Studies on effect of age of fruit, age of inoculum and inoculum load were tested for per cent disease incidence of A. alternata. The maximum disease incidence (15.90 and 18.26%) was observed on four days old fruits at 4th and 7th days after incubation inoculated with 10 days old inoculum and with 106 inoculum load (spores/ml) at 25±1°C temperature.

Altemaria fruit rot caused by Alternaria alternata was observed on fruits of brinjal (Solanum melongena L.) as dark-brown-black concentric rings. To understand the cultural behaviour of the fungus, in vitro studies were carried out in the Department of Plant Pathology, SKN College of Agriculture, Jobner, Jaipur. Six different solid growth media viz., Potato dextrose agar (PDA), Oat meal, Corn meal, Czapeck's dox, Martins medium and Richards's medium were tested for mycelial growth and sporulation of A. alternata. The maximum mycelial growth and excellent sporulation were observed on PDA (47.70 and 84.28 mm) followed by Richards' medium (38.28 and 76.70 mm) after 4th and 7th days of incubation at 25±1°C. Minimum mycelial growth of the fungus was observed on Martin's medium (20.20 and 38.70 mm) and showed fair sporulation after 4th and 7th days of incubation.

Alternaria fruit rot disease was observed on fruits of brinjal (Solanum melongena) at Jobner in Rajasthan. Alternaria alternata was isolated from fruits and observed to be pathogenic under artificial conditions. Various fungicides, plant extracts and biological agents were tested against the fungus and its culture behavior such as mycelial growth and sporulation were observed under in vitro conditions. Among fungicides mancozeb (1000ppm) was found most effective in inhibiting mycelial growth and sporulation of A. alternata followed by copper oxychloride and iprodione (1000ppm). Garlic extract at 15% concentration inhibited mycelial growth and sporulation of the fungus followed by neem and onion in poisoned food technique. Trichoderma viride was found most effective biocontrol agent and produced a clear inhibition zone followed by Trichoderma harzianum and Sporidiobolus pararoseus.