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STUDIES ON SEEDBORNE FUNGI OF SOYBEAN AND ITS MANAGEMENT

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Title STUDIES ON SEEDBORNE FUNGI OF SOYBEAN AND ITS MANAGEMENT
 
Creator VENUGOPAL RAO, THOTA
 
Contributor RAJESWARI, B
 
Subject additives, crossing over, heterosis, diseases, sowing, yields, developmental stages, genes, genetics, planting
 
Description Charcoal rot / dry root rot caused by Macrophomina phaseolina is an
economically important seed and soil borne disease causing significant yield losses in
soybean. The pathogen causes charcoal rot, seedling blight, dry root rot, ashy stem
blight and dry wilt diseases. Annual lossess due to charcoal rot in soybean was to an
extent of 30 – 50%. Disease free quality seed production in soybean is utmost important
to sustain the productivity and maintain the quality of the crop. Keeping this in view,
detailed investigations were carried out to study the implication of seedborne fungi of
soybean on seed quality parameters and to find out suitable detection methods for
seedborne M. phaseolina. Studies on seed to seedling transmission of the pathogen and
its management through seed treatments using fungicides, bioagents, botanicals and
irradiations were made using soybean cv. JS-335.
A total of one hundred and twenty (120) seed samples comprising of soybean cv.
JS-335 were collected from major soybean growing districts of Andhra Pradesh i.e.,
Nizamabad (60 Nos) and Adilabad (60 Nos) during kharif 2012 - 2013. The seed
samples were analysed for seed health by standard blotter, 2, 4-D blotter, deep freeze
blotter and agar plate methods as per ISTA (1996). Significant differences in occurrence
of total number of fungal colonies due to location and source of seed samples were
observed. Total per cent occurrence of seed mycoflora in Nizamabad and Adilabad
districts of Andhra Pradesh was ranged from 30 to 49.2 % and 23.6 to 45.0 % by blotter
method, 14.8 to 28.1% and 11.6 to 22.1% by 2, 4 - D blotter method, 11.8 to 19.3 % and
9.5 to 16.2 % by deep freeze blotter method, 13.1 to 37% and 15.4 to 26.4 % by agar
plate methods, respectively. A total of nine fungal species belonging to eight genera
were detected in all the seed samples tested in four detection methods. Nine fungal flora
viz., Macrophomina phaseolina, Colletotrichum dematium, Aspergillus flavus,
Aspergillus niger, Rhizopus, Curvularia sp. Alternaria, Cladosporium and Fusarium sp.
were observed. Among them, pathogenic fungi viz., Macrophomina phaseolina,
Colletotrichum dematium, Curvularia sp. Alternaria, Cladosporium and Fusarium sp.
and storage / saprophytic fungi like Aspergillus flavus, Aspergillus niger and Rhizopus
were observed.
Of the four detection methods adopted for isolation of seed mycoflora in soybean,
standard blotter method was found superior in recording more number of total fungal
colonies in addition to predominant seedborne M. phaseolina over agar plate method, 2,
4 - D blotter and deep freeze blotter methods. Out of nine fungal species, M. phaseolina
was found predominant in the seed samples analysed (8.5 to 28.5 %) in Nizamabad and
Adilabad districts. The pathogen appeared as greyish mycelial growth on the incubated
seeds. Pathogenicity of seedborne M. phaseolina was proved by seed inoculation
method using soybean cv. JS-335. The pathogen was reisolated and compared with the
original isolate.
The mycoflora associated with soybean seed samples were found to reduced seed
quality parameters. Significant differences in mean seed germination (70.4 to 73.1 %),
mean seed vigour index I (1697 - 1821) and mean seed vigour index II (68.8 - 82.2) was
recorded. Among different Mandals, Ditchpally Mandal of Nizamabad district and
Kubeer Mandal of Adilabad district recorded low seed germination (65.3 % and 67 %),
seed vigour I (1394 – 1470) and seed vigour II (57.0 - 65.2) with increased seed rot
(19.2 % and 14.1 %) and seedling blights (17.3 % and 12.5 %). Seedborne fungi present
in soybean produced seed rots, seedling blights and decreased quality and quantity of
soybean besides causing germination failures.
Seed transmission of M. phaseolina in apparently healthy soybean seeds (cv. JS
335) was 6 % and 8 % and in artificially inoculated soybean seeds (38.5 % and 49 %)
and in naturally infected soybean seeds (32 % and 43.1 %). Germination in the above
seed samples ranged from 75% to 72%, 55% to 46% and 59.3 % to 50.5 % in test tube
water agar method (in vitro) and in glasshouse conditions.
The efficacy of seed treatments against seedborne M. phaseolina were evaluated
under glasshouse conditions. The results indicated that soybean seeds treated with
thiram + carbendazim @ 3 g kg-1 or vitavax power 200 @ 2.5 g kg-1 improved seed
germination (91%, 89%) and reduced seed rot (5.7 %, 6.7 %) and seedling blights (4.0
% and 5.2 %). Seed treatment with T. viride @ 10 g kg-1 was also found on par with
fungicide seed treatments in improving seed germination of 88 % and reducing seed rot
and seedling blight of 7.3% and 6.3%, respectively. Seed treatment with bioagent (P.
fluorescens), botanicals (neem seed kernel extract @ 5 % and neem leaf powder @ 5g
kg-1) and irradiations (1.5 k Gy and 2.5 k Gy) were also effective in improving seed
germination and reducing seedling mortality as compared to untreated seeds (74%, 20.7
% and 15.0 %) and pathogen treated seeds (60 %, 26.3 % and 25.7%), respectively in
soybean cv. JS-335.
 
Date 2016-06-13T12:20:33Z
2016-06-13T12:20:33Z
2013
 
Type Thesis
 
Identifier http://krishikosh.egranth.ac.in/handle/1/67267
 
Language en
 
Relation D9315;
 
Format application/pdf
 
Publisher ACHARYA N.G. RANGA AGRICULTURAL UNIVERSITY