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
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Creator |
INDUMATHI, S
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Contributor |
ESWARA REDDY, N.P
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Subject |
Alternaria LEAF, SUNFLOWER, Alternaria helianthi, Hansf, Tubaki, Nishihara
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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. |
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Date |
2016-06-02T11:43:47Z
2016-06-02T11:43:47Z 2011 |
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Type |
Thesis
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Identifier |
http://krishikosh.egranth.ac.in/handle/1/66627
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Language |
en
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Relation |
D8958;
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Format |
application/pdf
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Publisher |
ACHARYA N.G. RANGA AGRICULTURAL UNIVERSITY
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