“IN VITRO EVALUATION AND CHARACTERIZATION OF BIOCONTROL AGENTS ISOLATED FROM DIFFERENT AGRO-CLIMATIC ZONES OF ANDHRA PRADESH AGAINST MAJOR SOIL-BORNE PATHOGENS viz., Rhizoctonia solani, Sclerotium oryzae AND Fusarium oxysporum f.sp. ciceri ”
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Date
2024-05-06
Authors
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Acharya N G Ranga Agricultural University
Abstract
The present investigation was carried out to evaluate and to characterize
the biocontrol agents isolated from different agro-climatic zones of
Andhra Pradesh against major soil-borne pathogens viz., Rhizoctonia solani,
Sclerotium oryzae and Fusarium oxysporum f.sp. ciceri.
Infected plant samples of rice and chickpea were collected from the fields
of RARS, Nandyal. Three pathogens viz., Rhizoctonia solani, Sclerotium oryzae
and Fusarium oxysporum f.sp. ciceri were isolated from the diseased samples
and proved the pathogenicity. Twenty Trichoderma isolates showing high
antagonistic activity were collected from different Research stations of
ANGRAU, Andhra Pradesh and pure cultures of Trichoderma isolates were
maintained in PDA slants. All the twenty Trichoderma isolates were designated
based on the location and were evaluated against the three pathogens in vitro.
Twenty Trichoderma isolates were tested against R. solani in vitro. The
maximum inhibition per cent which was from 72.33 per cent to 33.67 per cent.
AT-6 Trichoderma isolate collected from Anakapalli Research station showed
highest inhibition of 72.33 per cent followed by AT-1 (67.33%), AT-4 (66.33%)
and AT-2 (65.67%) which were statistically on par with each other. The least
inhibition was observed with AT-5 isolate with 33.67 per cent. Based on the
results from this assay against R. solani, Trichoderma isolates viz., AT-6, AT-1,
AT-4, AT-2 were carried forward to test the mechanism of antagonistic activity
and their characterization.
When twenty Trichoderma isolates were tested against Sclerotium oryzae,
the maximum inhibition per cent was from 82.20 per cent to 44.40 per cent.
AT-4 isolate showed maximum growth inhibition of Sclerotium oryzae (82.20%)
followed by KT-1 (78.86%), AT-6 (77.76%) and AT-1(76.63%) which were on
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par with each other. The least inhibition was observed in NT-7 isolate (44.40%).
Based on the above results, Trichoderma isolates viz., AT-4, KT-1, AT-6 and
AT-1 were carried forward to test the mechanism of antagonistic activity and
their characterization.
When twenty Trichoderma isolates were tested for their antagonistic
potential against Fusarium oxysporum f.sp. ciceri, the maximum inhibition per
cent was from 60.17 to 33.33 per cent. Maximum per cent inhibition of 60.17%
per cent was observed with AT-6 isolate, followed by AT-2 (57.57%) and AT-1
(53.70%). Least per cent of inhibition was observed with AT-5 (33.33).
Of the twenty Trichoderma isolates were tested against three pathogens,
five Trichoderma isolates viz., KT-1, AT-1, AT-2, AT-4, AT-6 were selected
based on their performance in dual culture assay and carried forward to test the
antagonistic activity and their characterization.
Maximum mycelial growth inhibition of R. solani, S. oryzae,
Fusarium oxysporum f.sp. ciceri was due to production of volatile compounds by
AT-6, AT-4, AT-6 Trichoderma isolates respectively.
The effect of non-volatile compounds produced by potential Trichoderma
isolates against R. solani was similar in all the three concentrations viz., 50, 30
and 10 per cent with the highest mycelial growth inhibition of R. solani by
AT-6, S. oryzae by AT-4, Fusarium oxysporum f.sp. ciceri by AT-6 isolates
respectively.
Morphological characters of all five potential Trichoderma isolates viz.,
KT-1, AT-1, AT-2, AT-4, AT-6 like branching of conidiophores, shape and size
of phialides and conidia were studied. KT-1 and AT-2 showed Sigmoid or
hooked phialide shape and the size ranged in between 4.5-12.5 × 2.5-3.5 µm,
conidia were globose to ovoid and size between 3.6-4.8 × 3.5-4 µm. AT-1 isolate
showed ampulliform to lageniform phialides shape and size between 4.7–7.9 ×
2.3–3.5 µm, conidia were subglobose to ovoid and the size was between 2.5–3.2
× 2.2–2.8 µm. AT-4 and AT-6 isolates showed bottle shaped phialides and the
size ranged in between 6–11.5 × 2.5–2.9µm, conidia were ellipsoidal, subglobose
shaped and size ranged between 4–6 × 3.0–4.0 µm.
Tests for hydrolytic enzyme production viz., cellulases, proteases,
amylases were performed. Of the five potential Trichoderma isolates KT-1,
AT-4, AT-6 were positive for cellulase, AT-1, AT-4 and AT-6 isolates were
positive for amylase and KT-1 isolate was found positive and the remaining
isolates were found negative for protease production. AT-4, AT-6, KT-1, AT-2
isolates were positive for ammonia production. AT-1, AT-4, AT-6 isolates were
positive for HCN production. All the five isolates produced siderophores.
Molecular characterization of potential Trichoderma isolates viz., KT-1,
AT-1, AT-2, AT-4, AT-6 was done by using ITS-1 and ITS-4 primers.
Amplification of the 18S rDNA region from Trichoderma isolates with primers
ITS 1 and ITS 4 yielded products of approximately 600 bp. BLAST analysis
(BLAST) results showed that KT-1 and AT-2 isolates showed more per cent
identity with T. viride, AT-1 with T. harzianum and AT-4, AT-6 with
T. longibrachiatum
Description
Keywords
VITRO EVALUATION, BIOCONTROL AGENTS, AGRO-CLIMATIC ZONES, SOIL-BORNE PATHOGENS, ANDHRA PRADESH