Submitted to: Annual Beet Sugar Development Foundation Research Report
Publication Type: Research Notes
Publication Acceptance Date: 5/15/2009
Publication Date: 6/1/2009
Citation: McGrath, J.M., Hanson, L.E. 2009. Release of SR98 Sugarbeet Germplasm with High Levels of Resistance to Rhizoctonia Damping-Off, Crown and Root Rot, and Fusarium CD-ROM]. 2009 Annual Beet Sugar Development Foundation Research Report. Denver, Colorado: Beet Sugar Development Foundation.
Technical Abstract: SR98 (PI 655951) is a sugarbeet germplasm with smooth, low soil tare root and high levels of resistance to damping-off and crown and root rot caused by Rhizoctonia solani (AG2-2). Previous smooth–root releases have been highly susceptible to diseases caused by R. solani, and the SR98 has incorporated Rhizoctonia resistant germplasm released from the USDA-ARS Ft. Collins, CO, and East Lansing, MI, Rhizoctonia resistance breeding programs. SR98 has shown moderate yield potential in agronomic trials, and has shown reasonable resistance to Aphanomyces blackleg and Cercospora leaf spot as is customary of traditional East Lansing ARS germplasm. SR98 is expected to be used as a pollinator for developing hybrids adapted to the Great Lakes growing region. In the 2007 seedling Rhizoctonia nursery in East Lansing, SR98 had a September stand count of 30.0 plants (std. dev.=0, n=2 plots), compared with the resistant EL51 (mean=25.5, std. dev.=5.3, n=4) and a susceptible unrelated smooth-root breeding line SR IC-2 (mean= 2.0, std. dev.=1.4, n=2). In 2008, SR98 had a mean stand count in July of 25.7 plants (std. dev=3.5, n=7 plots), relative to the resistant EL51 (mean= 1.0, std. dev.=5.2, n=4) and the susceptible SP7322 (mean=2.5, std. dev.=0.6, n=4). Pre-inoculation stand counts taken June 29, 2008, for these three germplasms was 36.6 plants per plot (std. dev.=7.4) with no significant difference between germplasms at this stage. By July 27, 2008, SR98 retained 64% of initial stand (std. dev.=11%), the resistant EL51 retained 54% of initial stand (std. dev.=6%) and the susceptible SP6822 retained only 9% of initial stand (std. dev.=2%).