Registration of EL51 Sugarbeet Germplasm with Resistance to Rhizoctonia Crown and Root Rot

Sugarbeet (Beta vulgaris L.) germplasm EL51 (Reg. no. GP-205, PI 598074) was developed by the USDA-ARS and the Michigan Agricultural Experiment Station, in cooperation with the Beet Sugar Development Foundation, and released in January 1999. EL51 has extremely high resistance to crown and root-rotting strains (AG-2-2) of Rhizoctonia solani Kiihn. EL51 has moderate resistance to Cercospora leaf spot (caused by Cercospora beticola Sacc.) and to blackroot seedling disease and root rot (caused by Aphanomvces cochlioitles Drechs.). It provides a unique source for development of parental lines resistant to three of the most destructive sugarbeet diseases in the United States. EL51 is predominantly multigerm with 11% monogerm plants. It is non-Type-O. self-sterile, and segregates for red (87%) and green (13%) hypocotyls. EL51 originated from seed borne on four plants of multigerm line FC705/1 (PI 590754) selected for resistance to Rhizoctonia crown and root rot at East Lansing. MI in 1985, in a crossing block with a heterogeneous population of 87 other plants. This group of 87 plants was composed of 15 plants selected from multigerm line FC701/5 at East Lansing for resistance to Rhizoctonia crown and root rot, and 72 plants from ten families (81B19, 82B18, 83B8. 84B5, 84B6, 84B7, 84B8, 84B9, 84B10, 84B11) of the traditional East Lansing germplasm pool, both multigerm and monogerm, some bred for Rhizoctonia resistance. These 72 plants had been mass selected for resistance to Rhizoctonia crown and root rot or to Cercospora leaf spot. Seven plants, probably F, but some possibly produced from sib pollination, from seed borne on the four FC705/1 plants were mass selected for resistance to Rhizoctonia crown and root rot at East Lansing in 1987, and intercrossed to produce a population that was subjected to two cycles of recurrent selection for resistance to Rhizoctonia crown and root rot at East Lansing, with no less than twenty selected beets intercrossed in each generation. The resulting population was tested under the designation 96RR. EL51 is an increase of 96RR. EL51 is highly resistant to Rhizoctonia crown and root rot, scoring a significantly lower disease index (DI) than resistant checks FC705/1 and FC712 (PI 590766) (1.70 compared with 2.40 and 2.23, respectively; DI of 0 = no root rot, and 4 = all plants dead; LSD,,.,,, = 0.38) in the!997 USDA-ARS commercial cultivar evaluation at East Lansing. EL51 had moderate resistance to Cercospora leaf spot in the 1998 USDA-ARS evaluation at Ft. Collins CO, receiving a DI of 3.11 (average for three dates) compared with 2.83,2.89, and 4.22 (DI of 0 = no leaf spots and 10 = all plants dead; LSD(l.u; = 0.84) for the resistant check, EL50 (PI 598073), and the susceptible check, respectively. EL51 had a stand rating of 3.4 (moderately resistant) compared with 2.5 and 3.7 for SR87 and the resistant Michigan hybrid check in the 1997 Betaseed summer root rot (Aphanomyces) evaluation at Shakopee, MN (DI of 1 = full healthy stand, and 9 = all plants dead; LSD005 = 1.17). Sucrose concentration of EL51 was 88 percent of the mean of two commercial cultivars, ACH185 (American Crystal) and HME17 (Hilleshog-Novartis), in three tests at Saginaw, MI in 1996 and 1997. EL51 provides a source for the development of monogerm and multigerm parental lines and populations with resistances to crown and root rot and leafspot diseases. Breeder seed will be maintained by USDA-ARS and provided in quantities adequate for reproduction. Written requests should be addressed to J. Mitch McGrath. Seed of this release has been deposited in the National Plant Germplasm System where it will be available for research purposes, including development and commercialization of new cultivars. It is requested that appropriate recognition be made if this germplasm contributes to genetic research or to the development of a breeding line or cultivar.