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Forty four plant species and eight antagonistic organisms were tested against Colletotrichum capsici and Alternaria alternata, the causal agents of fruit rot disease of chilli. In vitro studies indicated that leaf extracts (10%) of Abrus precatorius (Gundumuthu) and Aegle marmelos (vilvum), demonstrated the highest inhibition of spore germination and mycelial growth of these two pathogens. Among the fungal and bacterial antagonists tested, Trichoderma viride isolate 3 and Pseudomonas fluorescens were very effective in inhibiting mycelial growth of the pathogens in vitro. In the pot culture experiment, two sprays with leaf extract of A. precatorius (10%), first spray 20 days after fruit set and the second spray 2 days after inoculation with the pathogens, resulted in the lowest disease incidence (23.95%) and intensity (27.60 PDI - Per cent Disease Index) as compared to 71.50% incidence and PDI of 78.20 in the control. Among the antagonistic microorganisms two sprays of talc-based formulation of P. fluorescens (2%) were very effective in reducing the disease intensity (35.70 PDI). However, the leaf extracts and antagonistic organisms only ranked next to the fungicide (carbendazim 0.1%) (18.05 PDI). Field evaluation of the effective plant extracts, antagonistic microorganisms and fungicide revealed that spraying with A. precatorius leaf extract (10%) twice, the first spray at the time of fruit set and the second spray 20 days after fruit set caused the maximum disease reduction (25.53 PDI) followed by a single spray of the same leaf extract (10%) on 20th day after fruit set (28.50 PDI).
The virulent isolates of Colletotrichum capsici and Alternaria alternata produced more cellulolytic enzymes viz., C1 and Cxin vitro than the avirulent ones and the activity of these enzymes increased with the increase in age of culture. The virulent isolates of C. capsici and A. alternata produced more pectinolytic enzymes (macerating enzymes, pectin methyl esterase and endo polygalacturonase) than the avirulent ones. All the pectinolytic enzymes were highly active in 10-day-old culture and the activities decreased with the increase of culture age. Whereas the activity of enzymes produced by avirulent isolate of pathogens did not decrease and these enzyme activities increased with the increase in the age of culture. These pathogens also produced nonspecific toxic metabolites in culture filtrate which reduced seed germination, root length, shoot length and vigour index of the seedlings of chilli, rice, mungbean, maize, cotton, groundnut, okra, egg plant, cucumber and tomato. The toxins of the pathogens reduced seed germination and caused mortality of chilli seedlings in pot culture. The toxins also produced phytotoxic symptoms in the treated ripe and green chilli fruits and leaves.
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