Carpogenic germination of sclerotia of Sclerotinia minor and ascosporic infection of pyrethrum flowers

O'Malley, Thomas B. and Hay, Frank S. and Scott, Jason B. and Gent, David H. and Shivas, Roger G. and Pethybridge, Sarah J. (2015) Carpogenic germination of sclerotia of Sclerotinia minor and ascosporic infection of pyrethrum flowers. Canadian Journal of Plant Pathology, 37 (2). pp. 179-187. ISSN 0706-0661

Abstract

Carpogenic germination of sclerotia and infection of flowers by ascospores of Sclerotinia minor is rare and seldom documented in most hosts. During 2007-2009, S. minor isolates were obtained from surface-sterilized pyrethrum flowers collected from fields in Australia. The isolation frequency of S. minor from flowers in 2007, 2008 and 2009 was 15.8%, 5% and 1.4%, respectively. During these years, the prevalence of S. minor in flowers amongst pyrethrum fields varied between 10.3% and 60%. Sclerotia with apothecia, consistent in size with S. minor, were collected in one field. Colonies from individual ascospores from this isolate were identified as S. minor. A subsample of 10 S. minor isolates was selected for further studies. Phylogenetic analysis based on the internal transcribed spacer region grouped these isolates with S. minor, and distinct from published sequences of other Sclerotinia spp. Species-specific primers developed previously to differentiate the four major Sclerotinia spp. (S. sclerotiorum, S. minor, S. homoeocarpa and S. trifoliorum) were used to confirm identity. Of the 10 S. minor isolates, eight were able to carpogenically germinate in vitro. Pathogenicity of S. minor to flowers was confirmed in the greenhouse using ascospores. This study is one of the few instances documenting the ability of S. minor to infect floral tissues and the first documentation of S. minor causing flower disease of pyrethrum. These findings serve as a scaffold for further investigations into the mechanisms of flower infection by S. minor and have implications for the management of the Sclerotinia disease complex affecting pyrethrum in Australia.


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Item Type: Article (Commonwealth Reporting Category C)
Refereed: Yes
Item Status: Live Archive
Additional Information: Files associated with this item cannot be displayed due to copyright restrictions.
Faculty / Department / School: No Faculty
Date Deposited: 24 May 2017 23:22
Last Modified: 01 Sep 2017 02:50
Uncontrolled Keywords: carpogenic germination; pyrethrum; Sclerotinia flower blight; Sclerotinia minor; Sclerotinia sclerotiorum; PLANT SCIENCE; PLANT PATHOLOGY AND SYMBIOSES; Plant Pathology; Fungi - general;
Fields of Research : 06 Biological Sciences > 0607 Plant Biology > 060704 Plant Pathology
07 Agricultural and Veterinary Sciences > 0703 Crop and Pasture Production > 070308 Crop and Pasture Protection (Pests, Diseases and Weeds)
Socio-Economic Objective: B Economic Development > 82 Plant Production and Plant Primary Products > 8203 Industrial Crops > 820303 Plant Extract Crops (e.g. Pyrethrum, Jojoba)
Identification Number or DOI: 10.1080/07060661.2015.1036122
URI: http://eprints.usq.edu.au/id/eprint/31517

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