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Abstract
The fungus Sclerotinia minor (IMI 344141) is being developed as a biological control for dandelion and other broadleaf weeds in turfgrass environments. Being a microbial pest control agent (MPCA), the S. minor strain must be characterized to show relatedness to like organisms and to distinguish the MPCA from related microorganisms. Phenotypic variation among 30 isolates of S. minor, collected from different regions and hosts, was studied on potato dextrose agar (PDA) and oatmeal agar (OMA). Isolates varied significantly in sclerotia shape (length/width ratio) and number, but did not vary in colony morphology or growth rates. There was high diversity (0.6) among the mycelial compatibility groups (MCG) as seven multi-member and 11 single member groups were recognized. Isolates were categorized into highly virulent, virulent, moderately virulent, and hypo virulent based on 48 h post mycelial growth on detached dandelion leaves. When assessed on dandelion plants in the greenhouse, isolate IMI 344141 ranked the highest in biocontrol efficacy, reduction of above- and below-ground biomass, and reduction in dandelion survival. Oxalic acid production was not correlated with isolate aggressiveness or growth rate and did not vary among isolates of the same MCG. IMI 344141 can be phenotypically distinguished from the other tested S. minor isolates by performing vegetative compatibility testing and counting sclerotia produced on standard 9-cm diameter PDA plates. IMI 344141 produces <100 sclerotia/plate.
Acknowledgements
The authors are grateful to Miron Teshler for his help in various aspects of the project. Financial support from the Natural Sciences and Engineering Research Council of Canada (NSERC) Idea to Innovation (I2I) grant and Sarritor Inc. are gratefully acknowledged. The following graciously loaned S. minor isolates: G. Abawi, Cornell University, Geneva, USA; G. Boland, University of Guelph; J. Whipps, Warwick Horticulture Research International, UK; H. Huang, Agriculture and Agri-food Canada, Brandon; P. Phipps, Virginia Tech; S. O'Neill, Queensland Dept. Plant Industry, Brisbane; Tamrika Hind-Lanoiselet, Wagga Wagga Agricultural Institute, NSW; S. Morley, Herbarium VPRI, Victorian Department of Primary Industries, Knoxfield, Victoria, Australia; K. Elena, Benaki Phytopathological Institute, Athens, Greece; Alison Stewart, Lincoln University, Christchurch, New Zealand; Levente Kiss, Hungarian Plant Protection Institute, Budapest; P. Charue, Belgian Coordinated Collections of Microorganisms, Louvain; J. Tatnell and M. Fuhlbohm, Australian Department of Plant Industry, Kingaroy, QSLD; W.G. Kim, National Institute of Agricultural Science and Technology, Suwon, Republic of Korea; F. Snippe-Claus, Centraalbureau voor Schimmelcultures, Utrecht, The Netherlands.