EFFECT OF AGRO CHEMICALS AND BIOCONTROL AGENTS ON THE VIABILITY OF SCLEROTIA OF RICE SHEATH BLIGHT PATHOGEN Rhizoctonia solani Kuhn.
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Date
2017
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Acharya N.G. Ranga Agricultural University
Abstract
The present investigation was carried out to study the effect of agro
chemicals and biocontrol agents on the viability of sclerotia of Rhizoctonia
solani Kuhn. Rice sheath blight pathogen R. solani was isolated from the
diseased samples obtained from Agricultural Research Station, Nellore. Its
pathogenicity was proved by using detached leaf technique.
The herbicides viz., Glyphosate, 2,4-D Sodium salt, Butachlor,
Pretilachlor, Oxadiargyl, Pyrazosulfuron ethyl, Bensulfuron methyl 0.6% +
Pretilachlor 6%, Cyhalofop-butyl, Bispyribac sodium and Ethoxy sulfuron
were tested at recommended concentrations were significantly superior over
control in checking the mycelial growth of R. solani. Glyphosate, Butachlor,
Pretilachlor showed 100 per cent inhibition.
Among the ten herbicides tested against sclerotial viability, only two,
viz., Butachlor and Pretilachlor were found to be effective in inhibiting the
sclerotial germination even at lower incubation period of 5 min. both in soil
application and in vitro. Glyphosate inhibited sclerotial germination at higher
incubation periods i.e., 18 h and 24 h. Rest of the herbicides tested were
ineffective in inhibiting the sclerotial germination even though they were
effective in inhibiting mycelial growth.
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Pseudomonas fluorescens isolates NLR-B1, NLR-B2, NLR-B3 were
tested in dual culture against R. solani among which NLR-B3 isolate was
found to be more antagonistic in vitro against R. solani than other two
isolates.
Sclerotial germination was tested after incubating in NLR-B3 bacterial
suspension in the concentrations from 10-4 to 10-8 CFU/ml, there was no
inhibition in sclerotial germination at 10 min incubation at all concentrations
of bacterial suspension, where as at 20 min incubation, inhibition of sclerotial
germination was 73.33 per cent at 10-4 concentration, 43.33 per cent at 10-5
concentration, 30 per cent at 10-6 concentration and there was no inhibition of
sclerotial germination at 10-7 and 10-8 concentrations. At the incubation period
of 30 min. inhibition in sclerotial germination was 53.33 per cent at 10-4
concentration, 36.67 per cent at 10-5 concentration, 30 per cent at 10-6
concentration. Similar inhibition of 13.33 per cent was observed both at 10-7
and at 10-8 concentration. Per cent inhibition increased with increase in
concentration of bacterial suspension at 20 and 30 min incubation periods.
The bacterial suspensions at the earlier concentrations were added to
the soil and incubated for 10 days after which the sclerotia were retrieved and
tested for their viability, the inhibition of sclerotial germination was 56.67 per
cent at 10-4 concentration, 36.66 per cent at 10-5 concentration and 16.66 per
cent at 10-6 concentration. However at lower concentration of 10
-7 and 10-8
there was no inhibition of sclerotial germination. There was a significant
increase in per cent inhibition of sclerotial germination with increase in
concentration of the bacterial suspension.
The efficacy of seed treatment with different fungicides viz.,
Carbendazim, Propiconazole, Hexaconazole, validamycin, Tebuconazole,
Thifluzamide, Azoxysrtrobin, Difenoconazole, Tebuconazole 50% +
Trifloxystrobin 25% (Nativo) on the viability of sclerotia admixtured with the
seed was tested, in which all the tested fungicides showed 100 per cent
inhibition of sclerotial germination in both wet and dry seed treatments.
The seed admixtured with sclerotia was treated with different
fungicides given above, and the effect of sclerotia on germination and
seedling growth was tested by paper towel and pot culture methods. All the
seed was germinated in both paper towel and pot culture methods. The
efficacy of fungicides on seedling growth varied in both wet and dry seed
treatments. All the tested fungicides showed increased seedling growth (root
length and shoot length) except Carbendazim and Tebuconazole 50% +
Trifloxystrobin 25% (Nativo) when compared to control in both paper towel
and pot culture methods.
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Effect of Trichoderma silver nano particles on mycelial growth of R.
solani at three different concentrations i.e., 75, 100 and 125 ppm were tested.
Among the three concentrations, the highest inhibition (88.19 %) was
observed at 125 ppm followed by 100 ppm (52.93 %). The effect of
Trichoderma silver nano particles were also tested on sclerotial viability of R.
solani in vitro. Among the four tested concentrations (50, 75, 100 and 125
ppm) the highest per cent inhibition was observed at 125 ppm (85 %) followed
by 100 ppm (47.50 %)
Description
D5527
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