Submitted to: American Society of Sugar Beet Technologists
Publication Type: Proceedings
Publication Acceptance Date: December 16, 2010
Publication Date: March 2, 2011
Citation: Hanson, L.E., McGrath, J.M. 2011. Rhizoctonia seedling damping-off in sugar beet in Michigan. In: Proceedings of the American Society of Sugar Beet Technologists. 36th Biennial Meeting, March 2-5, 2011, Albuquerque, New Mexico. 2011 CDROM. Technical Abstract: Rhizoctonia solani is an important seedling pathogen of sugar beet, causing damping-off following seedling emergence. Anastomosis group (AG)-4 has been the primary seedling pathogen reported on sugar beet, however, recent screening has found high incidence of infection by AG-2-2. Isolations of R. solani were made from seedlings with symptoms in Michigan over a three-year period. Pure cultures were obtained after hyphal tip transfer. AG determination was done via paired isolate testing and molecular methods. Intraspecific group was determined by growth at 22 C and 35 C and pathogenicity was confirmed on sugar beet seedlings. In each year, AG-2-2 predominated on seedlings collected in Michigan. Over half of these had high temperature tolerance, characteristic of AG-2-2 IIIB. Germplasm showed variability in response to different isolates of both AG-2-2 and AG-4. Resistance to AG-2-2 IIIB was found in ARS germplasm, such as EL51 and SR98, with good plant survival in both greenhouse and field screening. An understanding of the prevalence of different AG and ISG is important to determine the impact of resistance, and to ensure resistance screening targets the more prevalent pathogens.