In vitro evaluation and characterization of biocontrol agents isolated from different Agro climatic zones of Andhra Pradesh against major soil-borne pathogens of groundnut
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Date
2024-05-01
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Acharya N G Ranga Agricultural University
Abstract
Soil borne pathogenic fungi are of major concern in agriculture which
significantly reduce the plant yield. Management through chemicals imposes
environmental threats potentially dangerous to both humans as well as to animals.
The present study's main goal was to identify and assess efficient Trichoderma
spp. for biocontrol of the principal groundnut soil-borne diseases Aspergillus
niger, Rhizoctonia bataticola, and Sclerotium rolfsii. The investigation of
morphology, bio-efficacy, and biochemical synthesis (enzymes and antifungal
chemicals) is crucial to agents (BCAs) select high potential bio control against
complex plant pathogens and to confirm the mycoparasitic antagonistic capacity
of Trichoderma. In the current study twenty isolates were evaluated against soil
borne pathogens.
In dual culture the interactions of Trichoderma isolate with s.rolfsii
observations on fourth day of incubation showed that among different isolates
tested Trichoderma isolate KT-3 recorded significantly high per cent of inhibition
(76.67%) and least mycelial growth of S.rolfsii (2.10cm).
Observations on sixth day of incubation revealed that, Trichoderma isolate
NT-3 (80.37%) showed highest per cent of inhibition and lowest mycelial growth
of A.niger (1.77cm) and appeared to be significantly superior among the 20
isolates followed by Trichoderma isolate- KT-1 (78.15%) and AT-1(76.30%)
against A.niger. Against R. bataticola observations on sixth day of incubation
revealed that the inhibition per cent ranged from (75.56% - 52.96%) Trichoderma
isolate AT-6 showed least mycelial growth (2.33cm) and maximum inhibition
(75.56%) of growth of R. bataticola. Selection of potential isolates of Trichoderma
spp. against soil-borne pathogens, is done based on per cent inhibition (Bell’s scale
method). Among the 20 isolates tested it appeared that five isolates of Trichoderma
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spp. (AT-1, AT-6, NT-3, KT-1 and KT-3) were showing highest per cent inhibition
against three pathogens on an average and falling under the category of Group 2.
Selected isolates were further evaluated to test screen their lytic enzyme ability,
volatile and non-volatile efficacy.
Among five Trichoderma isolates tested for the antifungal volatile
metabolites production against the pathogens, isolate KT-3 showed high per cent
of inhibition (49.63%) and least mycelial growth of S. rolfsii (4.53cm) and differed
significantly with other Trichoderma isolate against S. rolfsii. Isolate NT-3 was
recorded maximum growth inhibition (80.00%) least mycelial growth of A. niger
(1.80cm) and found significantly superior over Trichoderma isolate KT-1 (76.3%),
AT-1 (72.22%), AT-6(68.89%) and KT-3(62.59%). Isolate AT-6 showed
significantly higher per cent of inhibition (59.62%) and least mycelial growth of
R. bataticola (3.67cm) followed by Trichoderma isolate KT-1 (49.26%) and
Trichoderma isolate NT-3(40.00%).
When cultrate filtrate of Trichoderma isolates tested at different
concentrations viz., 10, 30 and 50 per cent concentrations, at 50% concentration
highest rate of inhibition was noticed. Among the five isolates at 50 per cent
concentrations against S. rolfsii Trichoderma isolate KT-3(78.89%) showed
highest per cent of inhibition followed by AT-1(76.67%). On the sixth day
maximum inhibition against A. niger was noted on NT-3(85.56%) followed by
Trichoderma isolate KT-1(84.81%) which are on par with each other. The least
inhibition was observed in the isolate KT-3(75.56%). Against R. bataticola,
Trichoderma isolate AT-6 (74.44%) showed highest inhibition followed by
Trichoderma isolate KT-3 (73.33%) which are at par with above isolate.
Trichoderma isolate were grouped based on the morphological characters likes
sporulation type, shape and size of conidia, branching pattern, phialides length AT
1 and KT-3 recognized as T. harzianum, KT-1 as T. viride, NT-3 as T. asperllum,
and AT-6 as T.longibrachiatum.
When biochemical characterization of five potential isolates were screened,
Trichoderma isolate AT-6, NT-3 and KT-1 showed positive results for cellulase
test. Isolates KT-1 showed positive for protease test. For amylase test KT-3, NT-3
and AT-1 showed positive with halo zone formation and for siderophore assay all
the isolates showed positive results and for HCN assay the Trichoderma isolate
KT-1, AT-6 and NT-3 showed positive results. For NH3 assay KT-1, NT-3, AT-6
and KT-3 showed positive.
The potential Trichoderma spp. were identified at molecular level using ITS
1 and ITS 4 primers and based on the per cent similarity from the NCBI data base
showed that out of five isolates two isolates Trichoderma isolates-AT-1 and KT-3
were identified as Trichoderma harzianum and Trichoderma isolate-AT-6 as
Trichoderma longibrachiatum, NT-3 as Trichoderma asperellum and KT-1 as
Trichoderma asperellum (Trichoderma viride).