Monday, November 13, 2006 - 9:45 AM

Identification of Genotypes of Annual Bluegrass (Poa annua L.) with Contrasting Resistance to Pink Snow Mold.

Annick Bertrand1, Yves Castonguay1, Tom Hsiang2, Luc Couture1, and Julie Dionne3. (1) Agriculture and Agri-Food Canada, 2560 Hochelaga Blvd, Quebec City, QC G1V 2J3, Canada, (2) Dept. Environmental Biology, University of Guelph, Guelph, ON N1G 2W1, Canada, (3) Royal Canadian Golf Association, Suite 1 - 1333 Dorval Drive, Oakville, ON L6M 4X7, CANADA

Freezing stress and infection of cool season grasses by snow molds often result in widespread damage to golf greens in the spring.  Alternatives to current preventive application of fungicides in the fall are required to control snow molds in the context of reduction of fungicide use on golf greens.  The development of plant material more tolerant to freezing and less susceptible to snow molds is the most sustainable approach to improve winter survival and quality of putting surfaces.  The objectives were to: 1) develop a screening procedure for snow mold susceptibility; 2) identify genotypes with contrasting levels of resistance to pink snow mold, caused by Microdochium nivale.  To reach these goals, 30 genotypes were collected on golf greens across Quebec and Ontario and vegetatively propagated under controlled conditions.  After preliminary experiments, the following screening conditions were selected.  Genotypes were cold acclimated at 2°C for 2 weeks followed by 2 weeks at -2°C.  Genotypes were then inoculated with a mixture of 4 isolates of M. nivale that were grown on wheat bran and applied at a rate of 10 mg cm-2.  Plants were incubated for 7 weeks at 2°C under high relative humidity (>99%). Snow mold development was visually assessed using a modified Horsfall–Barratt scale.  Genotypes were then transferred to conditions for regrowth (21/17°C D/N) and scored for damage after one week and after two weeks using the modified Horsfall–Barratt system. The experiment was conducted as a completely randomized block design with 10 replicates each of uninoculated and inoculated treatments.  This screening approach allowed us to identify 3 genotypes of low susceptibility and 3 of high susceptibility to pink snow mold.  These contrasting selections of genetic material are currently under evaluation and will be used in further studies to unravel the genetic and molecular bases of resistance to pink snow mold.