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INTEGRATED DISEASE MANAGEMENT OF Alternaria LEAF SPOT OF SUNFLOWER CAUSED BY Alternaria helianthi (Hansf.) Tubaki and Nishihara

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Title INTEGRATED DISEASE MANAGEMENT OF Alternaria LEAF SPOT OF SUNFLOWER CAUSED BY Alternaria helianthi (Hansf.) Tubaki and Nishihara
 
Creator INDUMATHI, S
 
Contributor ESWARA REDDY, N.P
 
Subject Alternaria LEAF, SUNFLOWER, Alternaria helianthi, Hansf, Tubaki, Nishihara
 
Description Sunflower (Helianthus annuus L.) is one of the major oil seed crops grown in
the world. In India it occupies 4th place in terms of area and production. In A.P it is
grown in an area of 0.42 m ha with 0.427 mt production.
Sunflower is affected by Alternaria helianthi (Hansf) Tubaki and Nishihara,
causing Alternaria leaf spot an important disease with yield losses ranging from 60 to
80 per cent. Earlier reports indicated the development of resistance by the pathogen to
different fungicides due to continuous and indiscriminate usage. Hence, in the present
study, an attempt was made to isolate native potential antagonists against A.helianthi
and to evaluate their efficiency in combinations with different fungicides in vivo
conditions.
The Pathogen was isolated from infected plant showing typical Alternaria
symptoms viz., circular, dark brown to black lesions with concentric rings that
resemble a target pattern, purified and identified as Alternaria helianthi.
A total of 24 antagonistic microflora (4 fungi and 20 bacteria) were obtained
from phylloplane and leaf endophyte of sunflower using serial dilution method. Most
of the bacterial isolates were found to be effective in inhibiting the growth of
A.helianthi in dual culture as well as in culture filtrate experiment, but at varying
degrees. Among the 4 fungal isolates, one was identified as Trichoderma sps. (FP1).
All the fungal antagonists overgrew the pathogen, A.helianthi in dual culture
technique. Among the twenty bacterial isolates, the endophyte isolate, BE8 showed
the highest inhibition (62.42%) against A.helianthi in culture filtrate technique.It is
followed by BE10 showing inhibition (61.12%) which is followed by BP1 showing
inhibition (58.87%).
Sensitivity of A.helianthi to different fungicides viz., carbendazim + mancozeb
(0.3%), mancozeb (0.25%), iprodione (0.2%), propiconazole (0.1%), hexaconazole
(0.2%), copper hydroxide (0.3%), cymoxanil (0.15%) was assessed in poisoned food
technique. Propiconazole showed the highest rate of inhibition (88.12%) followed by
cymoxanil (87.62%).
Compatibility of the potential bacterial antagonist BE8 with the above
fungicides was evaluated using spectrophotometric method. The bacterial isolate, BE8
was highly compatible with propiconazole followed by cymoxanil and iprodione.
Since the tested bacterial isolate BE8 shown highest degree of compatibility with
propiconazole, propiconazole was selected as the effective fungicide. The in vitro
experimental results (Plate 14) revealed that volatile metabolites produced by
antagonistic bacteria BE8 and BE10 inhibited the mycelia growth of Alternaria
helianthi up to the extent of 47.60% and 24.35% over the control on the 10th day of
incubation under in vitro.
The efficacy of potential antagonist BE8 alone and in combination with
propiconazole (0.1%) was assessed in pot culture. The integrated treatment T6, of
BE8 and the fungicide, propiconazole imposed at 30 and 45 DAS, was found to be
effective with leaf spot score 2, followed by the treatment T5 (leaf spot score 3). The
treatment T1 was found to be least effective with leaf spot score 5.
RAPD banding profile with seven different random primers viz., OPA-2,
OPA-3, OPA-4, OPA-6, OPA-9, OPA-12 and OPD-3 revealed the existence of
genetic variability among the isolates and were classified into 3 main clusters.
Amplification of 16S rDNA with 63F and 1387R primers which are specific to
bacterial 16S rDNA produced approximately 1300 bp fragment. These results show
that all the antagonistic isolates are bacteria and belong to prokaryotes.
 
Date 2016-06-02T11:43:47Z
2016-06-02T11:43:47Z
2011
 
Type Thesis
 
Identifier http://krishikosh.egranth.ac.in/handle/1/66627
 
Language en
 
Relation D8958;
 
Format application/pdf
 
Publisher ACHARYA N.G. RANGA AGRICULTURAL UNIVERSITY