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Chemical and biological control of S...

Athukorala, Sarangi Nirosha Priyajeevani.

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Chemical and biological control of Sclerotinia diseases in sunflower and study of biocontrol mechanisms involved.

Record Type:	Language materials, printed : Monograph/item
Title/Author:	Chemical and biological control of Sclerotinia diseases in sunflower and study of biocontrol mechanisms involved./
Author:	Athukorala, Sarangi Nirosha Priyajeevani.
Description:	195 p.
Notes:	Source: Masters Abstracts International, Volume: 47-06, page: 3356.
Contained By:	Masters Abstracts International47-06.
Subject:	Agriculture, Plant Pathology. -
Online resource:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=MR48948
ISBN:	9780494489482

Chemical and biological control of Sclerotinia diseases in sunflower and study of biocontrol mechanisms involved.
Athukorala, Sarangi Nirosha Priyajeevani.

Chemical and biological control of Sclerotinia diseases in sunflower and study of biocontrol mechanisms involved. - 195 p.

Source: Masters Abstracts International, Volume: 47-06, page: 3356.

Thesis (M.Sc.)--University of Manitoba (Canada), 2008.

Sclerotinia sclerotiorum (Lib.) de Bary is a devastating pathogen affecting over 400 different crop species and causes head rot, root rot and wilt, and mid-stalk rot, in sunflower (Helianthus annuus L.) worldwide. The disease management strategies in Canada include mainly cultural practices like crop rotation, tillage practices since there are no highly resistant cultivars or registered fungicides available. Biological control of wilt using fungal antagonists has been mostly experimental. The use of bacterial agents against this pathogen in sunflower is uncommon in Canada. Therefore, two bacterial strains Pseudomonas chlororaphis PA23 and Bacillus amyloliquefaciens BS6 which exhibited in vitro and in vivo inhibition of S. sclerotiorum in canola were used with the fungicide Ronilan (vinclozolin) in a field study at Morden, Manitoba against head rot and wilt diseases in 2006 and 2007. In 2006 none of the strains or the fungicide was successful against head rot due to the high disease pressure that prevailed. However, with some modifications in the application procedure a reduction in head rot by PA23, BS6 and Ronilan could be observed in the 2007 head rot trial although the differences were not significant. Only Ronilan showed significant reduction of wilt in both years. In addition, growth promotion by these two strains was monitored in two field trials located at Morden and Winnipeg in 2007. None of the strains in both locations promoted growth of sunflower. The laboratory experiment carried out to determine the involvement of different genes in the production of organic antimicrobial volatiles by PA23 showed that none of the tested genes affect the antibiotic production but they seem to affect the amount of volatiles produced by PA23 to various extents. Further research is suggested to test this hypothesis. The greenhouse study to determine the effect of two different antibiotics, phenazine and pyrrolnitrin, produced by PA23 on its colonization ability showed that antibiotics play a role when nutrients in the rhizosphere become limited. In addition, various other factors including siderophores seem to affect its colonization efficiency, their antibiotic production and biocontrol ability. Antibiotic deficient mutants showed relatively reduced colonization ability compared to the wild type PA23. Furthermore, combining PA23 with mutant strains of PA23 also reduced its efficiency but the relative effect of one antibiotic-deficiency over the other was not clear. In the investigation of antibiotics produced by Bacillus sp. isolated from different habitats using PCR, the presence of biosynthetic genes for surfactin and iturin A were identified in 20/21 of strains. Only a few strains showed the presence of other antibiotic genes tested. Sequence analysis showed that BS6 was positive for all genes tested. The MALDI-TOF MS analysis further confirmed the production of particular antibiotics by these strains. This indicates that antibiosis may be one of the mechanisms involved in the biocontrol exhibited by these Bacillus strains. In summary, this study demonstrated the potential use of the fungicide Ronilan to control wilt of sunflower and the importance of studying the effect of environmental factors influencing the efficacy of a biocontrol agent when using it in the rhizosphere and the phyllosphere.

ISBN: 9780494489482Subjects--Topical Terms:

1028950
Agriculture, Plant Pathology.

Chemical and biological control of Sclerotinia diseases in sunflower and study of biocontrol mechanisms involved.
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100 1 $a Athukorala, Sarangi Nirosha Priyajeevani. $3 2096829
245 1 0 $a Chemical and biological control of Sclerotinia diseases in sunflower and study of biocontrol mechanisms involved.
300 $a 195 p.
500 $a Source: Masters Abstracts International, Volume: 47-06, page: 3356.
502 $a Thesis (M.Sc.)--University of Manitoba (Canada), 2008.
520 $a Sclerotinia sclerotiorum (Lib.) de Bary is a devastating pathogen affecting over 400 different crop species and causes head rot, root rot and wilt, and mid-stalk rot, in sunflower (Helianthus annuus L.) worldwide. The disease management strategies in Canada include mainly cultural practices like crop rotation, tillage practices since there are no highly resistant cultivars or registered fungicides available. Biological control of wilt using fungal antagonists has been mostly experimental. The use of bacterial agents against this pathogen in sunflower is uncommon in Canada. Therefore, two bacterial strains Pseudomonas chlororaphis PA23 and Bacillus amyloliquefaciens BS6 which exhibited in vitro and in vivo inhibition of S. sclerotiorum in canola were used with the fungicide Ronilan (vinclozolin) in a field study at Morden, Manitoba against head rot and wilt diseases in 2006 and 2007. In 2006 none of the strains or the fungicide was successful against head rot due to the high disease pressure that prevailed. However, with some modifications in the application procedure a reduction in head rot by PA23, BS6 and Ronilan could be observed in the 2007 head rot trial although the differences were not significant. Only Ronilan showed significant reduction of wilt in both years. In addition, growth promotion by these two strains was monitored in two field trials located at Morden and Winnipeg in 2007. None of the strains in both locations promoted growth of sunflower. The laboratory experiment carried out to determine the involvement of different genes in the production of organic antimicrobial volatiles by PA23 showed that none of the tested genes affect the antibiotic production but they seem to affect the amount of volatiles produced by PA23 to various extents. Further research is suggested to test this hypothesis. The greenhouse study to determine the effect of two different antibiotics, phenazine and pyrrolnitrin, produced by PA23 on its colonization ability showed that antibiotics play a role when nutrients in the rhizosphere become limited. In addition, various other factors including siderophores seem to affect its colonization efficiency, their antibiotic production and biocontrol ability. Antibiotic deficient mutants showed relatively reduced colonization ability compared to the wild type PA23. Furthermore, combining PA23 with mutant strains of PA23 also reduced its efficiency but the relative effect of one antibiotic-deficiency over the other was not clear. In the investigation of antibiotics produced by Bacillus sp. isolated from different habitats using PCR, the presence of biosynthetic genes for surfactin and iturin A were identified in 20/21 of strains. Only a few strains showed the presence of other antibiotic genes tested. Sequence analysis showed that BS6 was positive for all genes tested. The MALDI-TOF MS analysis further confirmed the production of particular antibiotics by these strains. This indicates that antibiosis may be one of the mechanisms involved in the biocontrol exhibited by these Bacillus strains. In summary, this study demonstrated the potential use of the fungicide Ronilan to control wilt of sunflower and the importance of studying the effect of environmental factors influencing the efficacy of a biocontrol agent when using it in the rhizosphere and the phyllosphere.
590 $a School code: 0303.
650 4 $a Agriculture, Plant Pathology. $3 1028950
690 $a 0480
710 2 $a University of Manitoba (Canada). $3 1018707
773 0 $t Masters Abstracts International $g 47-06.
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791 $a M.Sc.
792 $a 2008
793 $a English
856 4 0 $u http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=MR48948