Evaluation of plant extracts and biocontrol agents against leaf spot disease of brinjal.

摘要

The antifungal properties of neem (Azadirachta indica) seed extract, and onion, garlic, bael (Aegle marmelos) and bitter melon (Citrullus colocynthis) extracts at various concentrations (5, 10 and 15%) were evaluated against Alternaria alternata by poisoned food technique. The efficacy of the extracts in the inhibition of mycelial growth increased with the increase in extract concentration. The garlic extract was the most inhibitory among the extracts (mean inhibition of 73.7%). In a pot experiment, aubergine seedlings were inoculated with A. alternata, and then sprayed with each of the extracts at 48 h after inoculation and 10 days thereafter. The plant extracts reduced the disease incidence (seedling mortality) and disease intensity (leaf spot), with the garlic extract being the most effective (mean reduction of 6.6 and 30.7%, respectively). The antagonistic potential of Trichoderma harzianum, T. viride and Aspergillus niger against A. alternata was evaluated by dual culture plate method on PDA medium. T. harzianum and T. viride inhibited the growth of the pathogen. T. harzianum was the most effective (inhibition zone of 7.3 mm), followed by T. viride (6.2 mm). Aubergine seeds were inoculated with the fungal antagonists (1.0 x 104 cfu [colony-forming units]/ml), inoculated with A. alternata, and then treated with 10-day-old cultures of the fungal antagonists before sowing. At 60 days after sowing, the pathogen was inoculated to plants. The fungal antagonists reduced seedling mortality and leaf spot intensity. Seedling mortality and disease intensity were lowest (9.3 and 38.5%, respectively) in plants treated with T. harzianum.