STUDIES ON ANTHRACNOSE OF SOYBEAN INCITED BY Colletotrichum truncatum ( Schw.) Andrus and Moore
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Date
2019
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PROFESSOR JAYASHANKAR TELANGANA STATE AGRICULTURAL UNIVERSITY
Abstract
Soybean anthracnose caused by Colletotrichum truncatum (Schw.) Andrus and
Moore is one of the most important seed borne diseases of soybean. Detailed
investigations were carried out on symptomatology, isolation and identification of the
pathogen, cultural and morphological characterization of the pathogen, in vitro
evaluation of fungicides, bioagents and botanicals against test pathogen, screening of
soybean germplasm/ genotypes against anthracnose pathogen was tested both under in
vitro and under glasshouse conditions. The disease reaction of available soybean germ
plasm/genotypes against pathogen was taken up. Integration of seed treatments using best
fungicide, potential bioagent and effective botanical were tested either alone or in its
combination by using soybean cv. JS 335 by rolled paper towel method. Integrated
disease management (IDM) adopting seed treatments with bioagents, fungicides and
botanicals either alone or in combination against anthracnose of soybean was attempted
under glasshouse conditions.
Soybean infected plant samples with anthracnose pathogen (leaf, stem and pod)
were collected from major growing areas of Adilabad and Jagital district of Telangana
state and Bidar district of Karnataka state during kharif, 2018. The disease is characterized
by appearance of reddish brown lesions on lower surface and later they turned to deep
dark brown and became chlorotic forming the lesions on both the surfaces. At later stages,
the lesions appeared on petioles, stem and on pods. In severe cases premature defoliation
occured.
The pathogen was isolated and pathogenicity was confirmed on susceptible soybean
cv. JS 335 under glass house conditions. Based on cultural and morphological
characteristics, pure culture of the pathogen was identified as C. truncatum (Schw.)
Andrus and Moore. The colonies of C. truncatum were initially appear as white and later
turned to dark brown to black, acervuli were black in colour measuring 186.7 µm to 265.0
µm. Conidia were single celled, smooth walled, hyaline, curved and measuring 20.0 µm
to 23.3 µm.
Eight fungicides were tested for their efficacy under in vitro conditions by using
poisoned food technique. Among the fungicides, carbendanzim + mancozeb and
propiconazole gave cent per cent inhibition of mycelial growth of C. truncatum at
different concentrations of 500 ppm, 1000 ppm, 1500 ppm, 2000 ppm and 2500 ppm,
respectively.
The antagonistic potential of four bioagents viz., Trichoderma harzianum, T. viride,
Pseudomonas fluorescens and Bacillus subtilis under in vitro conditions by dual culture
technique. T. harzianum significantly inhibited the mycelial growth of the pathogen
(80.22%) followed by T. viride (72.55%).
The efficacy of ten botanicals at 10 per cent concentration on the radial growth of
C. truncatum was tested by using poisoned food technique. Highest mycelial
growth inhibition was observed in garlic extract (53.22%) followed by onion extract
(47.11%) Studies on compatibility of bioagent T. harzianum with effective fungicides and
botanical either alone or in combination indicated that T. harzianum was compatible to
carbendazim + mancozeb, garlic extract and carbendazim + mancozeb + garlic extract.
Fifteen soybean germplasm/ genotypes tested against C. truncatum on seed quality
indicated that significant differences in seed germination, seedling length and seedling
vigour of pathogen uninoculated and inoculated soybean seeds was ranged from 20 to 36,
3.2 to 15.6 and 393 to 1775, respectively.
Screening of fifteen soybean germplasm/ genotypes against C. truncatum under
glasshouse conditions indicated that four germplasm/ genotypes viz., GPAS 23, GPAS
27, GPAS 65 and KDS - 726 were found moderately resistant with disease severity of
7.88 per cent to 10.1 per cent eight germplasm/ genotypes viz., MACS 1188, MACS 1281,
JS 20-69, BASARA, MACS 612, GPAS 62, GPAS 49 and GPAS 36 were moderately
susceptible and recorded disease severity of 13.83 per cent to 23.76 per cent and three
genotypes viz., JS 335, JS 20- 29 and JS 9305 were found susceptible and recorded disease
severity of 40.55 per cent to 43.76 per cent in reaction against anthracnose pathogen.
Seed treatment with carbendazim + mancozeb and garlic extract either alone or in
combination using soybean susceptible cv. JS 335 recorded seed quality parameters viz.,
seed germination (56% to 72%), seedling length (13.6 cm to 16.2 cm) and seedling vigour
index (758 to 1165) in uninoculated seeds over pathogen inoculated seeds (52%, 12.05
cm and 626).
Integrated disease management (IDM) using susceptible cv. JS 335 indicated that
seed treatment with carbendazim + mancozeb + garlic extract + T. harzianum was found
effective in increasing seed germination (50%) and reducing disease severity (6.34%)
followed by seed treatment with carbendazim + mancozeb + garlic extract which
recorded 50 per cent seed germination and 9.52 per cent disease severity. Where as in
pathogen inoculated control, seed germination (25%) and disease severity (85.18%) were
recorded.
Evaluation of fifteen soybean germplasm/ genotypes prior to inoculation with
pathogen using effective seed treatment with carbendazim + mancozeb +garlic extract +
T. harzianum by rolled paper towel method enhanced all seed quality parameters
viz., seed germination, seedling length and seedling vigour index (68% to 88%, 13.84 cm
to 17.75 cm and 941 to 1482) as compared to the pathogen inoculated seeds of soybean
cv. JS335 (52%, 12.05 cm, 626).
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