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MANAGEMENT OF PURPLE BLOTCH OF ONION CAUSED BY ALTERNARIA PORRI (Ellis) Cif.

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Title MANAGEMENT OF PURPLE BLOTCH OF ONION CAUSED BY ALTERNARIA PORRI (Ellis) Cif.
 
Creator Yadav, P. M.
 
Contributor RAKHOLIYA, K. B.
 
Subject diseases, fungi, onions, yields, fungicides, bacteria, land resources, biological phenomena, planting, pathogens
 
Description Onion (Allium cepa L.) is one of the most important, delicious and vitamin rich vegetable crop. The crop is subject to attack by a number of diseases caused by fungi, bacteria, viruses and nematodes which are the major constraints for higher production of the crop. Among the several diseases, purple blotch disease of onion (Allium cepa L.) caused by Alternaria porri (Ellis) Cif., is one of the most destructive disease causing accountable losses of about 80 to 90 per cent. Present investigations on the purple blotch disease was carried out during rabi 2011-12 and 2012-13 with the objectives viz., survey, isolation, pathogenicity, epidemiology, induced disease resistance with bioagents, evaluation (in vitro and in vivo) of fungicides and bioagents in the Department of Plant Pathology, N. M. College of Agriculture and College farm, N. A. U., Navsari.
The test pathogen was successfully isolated on potato dextrose agar and proved its pathogenicity on onion cv. Pilipatti under greenhouse conditions. The maximum sporulation was observed at 8 a.m. with high humidity and decreased towards noon with peak spore were spread at 12 noon and minimum at 8 a.m. The use of Pseudomonas fluorescens as a pre-treatment induced disease resistance against A. porri and reduced disease severity.
During laboratory screening, all tested fungicides caused significant inhibition of test pathogen over untreated control. However, among non-systemic fungicides, mancozeb was found best with highest (85.06%) mean
ABSTRACT
inhibition the radial growth of test pathogen. This was followed by copper oxychloride (77.57%) and thiram (75.05%). Among systemic fungicides, hexaconazole was found most effective and recorded significantly highest mean inhibition of radial growth (98.21%). This was followed by the propiconazole (97.32%) and difenoconazole (91.23%). The percentage mycelial inhibition of the test pathogen was found to be increased with increase in concentrations of the test fungicides.
All bioagents found antifungal / antagonistic in vitro against the test pathogen. Trichoderma viride was found most effective with significantly highest mycelial growth inhibition (94.71%) of the test pathogen followed by T. harzianum (91.13%) and T. koningii (88.85%). While in bacterial antagonist, Pseudomonas fluorescens-I was recorded 73.08 per cent mycelial growth inhibition.
The result obtained on the field efficacy of different fungicides revealed that, all the fungicides treatments significantly reduced the purple blotch disease intensity and significantly increased the bulb yield in onion cv. Pilipatti. Among the fungicides tested, hexaconozole (0.005%) was found most effective and recorded significantly least mean intensity (11.62%) with corresponding significantly increased bulb yield (41465 kg/ha). The next best fungicides were found propiconazole (0.025%) and tebuconazole (0.07%), which recorded significantly least mean disease intensity, respectively of 14.28, 15.62 per cent and gave corresponding maximum bulb yield of 36702 and 35864 kg/ha, respectively. Of the bioagents tested, Pseudomonas fluorescens-I (0.5%) was found most antifungal against A. porri and recorded significantly least mean disease intensity (37.19%) and gave maximum bulb yield (27183 kg/ha). Both the fungal and bacterial antagonists tested were also found effective against A. porri and recorded significantly reduced mean disease intensity there by increased the bulb yield over unsprayed control.
Based on incremental cost:benefit ratio (ICBR) of the fungicides treatments, hexaconozole (0.005%) which gave highest ICBR of 1:21.13 and was found to be most effective and economical for the management of purple blotch disease of onion. The next best fungicides were found propiconazole (1:18.33) and mancozeb (ICBR, 1:17.89). While among bioagents tested, Pseudomonas fluorescens-I (ICBR, 1:13.87) was found economical and effective for the management of purple blotch of onion followed by Bacillus subtilis (ICBR, 1:12.93).
 
Date 2016-05-03T10:51:18Z
2016-05-03T10:51:18Z
2013-05
 
Type Thesis
 
Identifier http://krishikosh.egranth.ac.in/handle/1/65740
 
Language en
 
Format application/pdf
 
Publisher Navsari Agricultural University, Navsari