Title: Evaluation of antagonists and natural plant extracts in controlling collar rot of groundnut caused by Aspergillus niger
Abstract: Forty five isolates of Trichoderma spp. were isolated from soil samples collected from groundnut growing fields of north-coastal zone of Andhra Pradesh and of them 10 morphologically different isolates were identified. The native isolates of Trichoderma spp. significantly inhibited the growth of Aspergillus niger over control. The isolates T1, T2, T18, T21 and T40 recorded more inhibition than others in dual culture and seeded agar methods. The extent of inhibition was more pronounced in seeded agar method than in dual culture method. The results revealed that all the ten bioagents tested in vitro applying dual culture technique against A. niger significantly inhibited the mycelial growth of the test pathogen over untreated control. However, Trichoderma isolate T21 recorded minimum colony diameter (2.07 cm) and highest inhibition (75.44%) of mycelial growth of A. niger over untreated control followed by the T1 and T40 which recorded mean colony diameter of 2.50 cm, 2.53 cm and mean mycelial inhibition of 70.34%, 69.99%, respectively. Where as in seeded agar methods maximum inhibition was recorded in T1 (85.00%) followed by T2 (81.93%) and T21 (81.11%). The native isolates of Trichoderma spp. showed a clear cut superiority over commercial formulations. But the commercial formulation of bacterial antagonist Bacillus subtilis showed significantly more antagonistic effect on the growth of A. niger than native isolates. Evaluation of different botanicals by poisoned food technique showed that all plant extracts tested in vitro were found significantly effective in reducing the percentage mycelial growth of Aspergillus niger over untreated control. However, plant extract (@ 5, 10 and 15% of garlic, recorded lowest mean colony diameter (1.57 cm) and highest mean mycelial growth inhibition (81.51%) followed by Polyalthia longifolia, Annona squamosa and Pongamia glabra which recorded the mycelial growth of 3.38 cm, 3.75 cm, 3.87 cm and the mean mycelial growth inhibition of 60.18%, 55.87%, 54.44% respectively. Among the concentrations and plant extracts, A. sativum (@10 and 15%) was most effective in reducing the growth of A. niger (100%) followed by Polyalthia longifolia @15% (77.73%), Annona squamosa @ 15% (74.61%) and Pongamia glabra @ 15% (70.33%). When plant extracts compared with the isolates of Trichoderma spp., P. fluorescens and B. subtilis showed inhibition of growth of the A. niger which ranged from 62.95 to 100.00 per cent. A. sativum showed the highest inhibition of growth of A. niger (100.0%) followed by B. subtilis and Trichoderma T1 isolate, which caused 84.52 and 84.49 per cent growth reduction of A. niger, respectively.
Publication Year: 2014
Publication Date: 2014-01-01
Language: en
Type: article
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