Coniothyrium rose canker in Oregon Public Deposited

http://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/k0698c819

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  • An isolate of Coniothyrium obtained from a stem canker on Nocturne rose from the Botany Department Farm, Corvallis, Oregon was studied with respect to morphological and cultural characters, pathogenicity and mineral nutrition. The hyphae of the isolate were smooth, septate and branched. The hyphal cells averaged 16.37 X 3.52 microns. The conidia were produced within black, carbonaceous pycnidia with pseudoparenchymatous walls five to six cells thick. Pycnidia averaged 286 X 256 microns. Conidia were extremely small, unicellular, oval shaped and hyaline, 1orne singly on stalk like projections from the innermost cells of the pycnidial wall. The conidia averaged 4.18 x 2.95 microns. On the basis of conidial character, the isolate was considered as Coniothyrium fuckelii, and synonymous with Coniothyrium rosarum. C. fuckelii gained entrance into the host only through wounds. At first penetration was primarily from cell to cell, in the cortex but later extended to part of the vascular cylinder and the pith. The fungus was intracellular. Incubation period was four to five days. The pathogen rarely entered through pruning wounds and did not infect rose leaves. Disease development occurred at temperatures from 10 to 30° C, the optimum being 25° C. This coincides with the optimum for growth of the fungus in culture, The canker lesions developed more rapidly on young succulent stems than on older canes. Rose varieties differed in susceptibility to infection by C. fuckelii. High levels of nitrogen in unbalanced nutrient solutions had a significant effect on size of lesions produced on inoculated rose stems. Whether the increased severity of infection was the result of an effect on the pathogen or increased succulence of the host tissue was not indicated. The callus which sometimes formed above the canker lesion resulted from proliferation of parenchymatous cells in the lower areas of the cortex but was not directly associated with the Coniothyrium infection. Germinating conidia began to send out a single hyaline germ tube after 18 hours incubation. Five percent sucrose solution proved to be the best medium for germination of conidia. Conidia germinated over a range of pH from 3 to 10 with maximum germination at pH 5. In general, acidity seemed to favor germination. Continuous darkness was more or less inhibitory. Minimum temperature for mycelial growth and for formation of pycnidia on PDA was approximately 5° C, the maximum was approximately 35° C and the optimum was 25° C. Coniothyrium fuckelii utilized fructose and mannose as sources of carbon and ammonium tartrate, casein hydrolysate. and urea as sources of nitrogen. Growth occurred within a pH range f 3.0 to 9.0, with optimum growth at a initial pH of 4.0. Numerous pycnidia were formed in media with initial pH values from 3.0 to 7.0. White light exerted a strong effect on pigment production in themycelium and on pycnidial formation. It also enhanced canker development on the rose canes. Young cultures of the fungus produced both submerged and aerial mycelium that was at first white and fluffy but became buff colored, then light brown as the culture aged. White light caused formation of a dark-green colored mycelium.
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