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| Web URL(s): | http://archive.lib.msu.edu/tic/rpr/1998/61834,Cornell,%20Harman.PDF
Last checked: 04/30/2013
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| Publication Type:
| Report |
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| Material Type: | Manuscript |
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| Monographic Author(s): | Harman, Gary E.; Nelson, Eric B.; Ondik, Kristen L. |
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| Author Affiliation: | Harman and Ondik: Department of Horticultural Sciences, Cornell University, Geneva, NY; and Nelson: Department of Plant Pathology, Cornell University, Ithaca, NY |
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| Monograph Title: | The Basic Biology and Etiology of Sclerotinia homoeocarpa, the Casual Agent of Dollar Spot: 1998 USGA Annual Report, 1998. |
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| Publishing Information: | Geneva, New York; Ithaca, New York: Cornell University |
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| # of Pages: | 5 |
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| Collation: | 4, [1] pp. |
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| Abstract/Contents: | "This research thus far has been designed primarily to focus on the following objective: To examine the development, including possible apothetical production, of the pathogen in creeping bentgrass greens when present in leaf tissue, in root tissue, or as isolated stroma and to determine the length of survival of the pathogen in infected tissue or as stroma. This is the first year of funded research. A summary of observations and tentative conclusions from the first field season are provided below together with action plans for the upcoming months. Small (2 x 4 cm) porous nylon bags were prepared, inoculum of S. homoeocarpa, in the form of infected grass or grown on sterile wheat, was placed in the bags, the bags were heat-sealed and they were buried vertically in bentgrass greens. The upper edge of the bags was even with soil line. The bags containing the wheat-based inoculum caused low levels of disease shortly after burial. Conversely, the bags with the turf-based inoculum rarely, if ever, caused disease. Disease was attributed to the bags since the natural epiphytotic had not occurred yet in this area. At the time of the natural epiphytotic in August and September, NO disease from the bags occurred from either inoculum type. Reisolation of S. homoeocarpa from the internal region of the bags resulted in slow-growing colonies that were almost overlooked due to the great difference in the growth patterns and morphologies of the laboratory culture. S. homoeocarpa's normal growth type is rapid and floccose. This morphotye occurs in laboratory-adapted cultures and is obtained is the pathogen is isolated from infected turf. The slow-growing phase of the organism and the rapid-growing phase are very different. After a week of incubation, the slow-growing S. homoeocarpa colonies from the buried inoculum suddenly begin to grow rapidly and become indistinguishable from the rapid-growing phase. The sudden explosive development is the only way that we could recognize the pathogen on the plates. We are still attempting to isolate the pathogen from the dark stromal area on the surface of the bags. These observations have permitted us to develop some concepts regarding how S. homoeocarpa may survive and cause epiphytotics. These are provided below. Data suggest that Sclerotinia homoeocarpa in soil has a slow-growing near-dormant phase that may not be infective. The lack of infectivity is suggested by the fact that the pathogen in our buried bags, which was in the slow-growing phase, did not cause disease during the time when natural epiphytotics were occurring. It is very difficult to isolate the fungus in this phase; this difficulty has no doubt has interfered with research on the presence, etiology and epidemiology of this disease. It may well be that Sclerotinia homoeocarpa has two phases - a near-dormant, heretofore undescribed, phase and the expected rapidly growing phase described by other researchers. It is tempting to speculate that the slow-growing (near-dormant) phase may be a survival mechanism and that the rapid-growing phase is the infective one. If so, then the mechanisms that cause the shift between the two phases could be the trigger for the onset of epiphytotics that are typical of the disease." |
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| Language: | English |
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| References: | 0 |
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| See Also: | See also related summary article, "The basic biology and etiology of Sclerotina homoeocarpa, the causal agent of dollar spot", 1998 Turfgrass and Environmental Research Summary [USGA], 1998, pp. 30-31, R=61834. R=61834 |
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| Note: | Also appears as pp. 3-7 in the USGA Turfgrass Research Committee Reporting Binders for 1998.
"USGA Annual Report, November 1998"
Tables |
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