Registration of Four Multigerm Sugarbeet Germplasms Resistant to Rhizoctonia Root Rot: FC716, FC717, FC718, and FC719

Sugarbeet (Beta vulgaris L.) germplasms FC716 through FC719 (Reg. no. GP-143 to GP-146, P1 574627 to P1574630) were developed by the USD A-ARS in cooperation with the Beet Sugar Development Foundation. Each of these germplasms was developed from genetically different and distinctive sources. These lines should provide resistance to root-rotting strains (AG-2-2) of Rhizoctonia solani Kilhn and potential pollinators with combining ability for yield. They were released in 1992. FC716 resulted from interpollination of 38 mother roots selected for resistance to rhizoctonia from three commercial hybrids, HH32 (66%), ACH-139 (24%), and 70MSH386 (10%). HH32 is a rhizoctonia-resistant Holly Sugar Corp. hybrid, ACH-139 is a rhizoctonia-resistant American Crystal Sugar Co. hybrid, and 70MSH386 is a rhizoctonia-resistant hybrid from the former Great Western Sugar Co. This initial population underwent five cycles of mass selection for rhizoctonia root rot resistance. FC716 has excellent rhizoctonia root rot resistance when tested under strong disease pressure (4). There were no significant differences between FC716 and resistant controls in disease index (D1) (2) or the percentage of healthy plants (4) (Table 1). It has low to medium resistance to cercospora leaf spot (caused by Cercospora beticola Sacc.) and is susceptible to curly top virus. FC716 is diploid, multigerm, and easy bolting and has medium sucrose content. It segregates for green hypocotyls (88%). All plants have the cytoplasmic factor for male sterility (CMS); «80% of the plants are pollen fertile (non-O-type) and 20% CMS. The fertile plants include Type 2, Type 3, and Type 4 pollen fertile plants. Nonetheless, it is a good pollen producer. It should have a low frequency of segregates for monogerm and O-type. Because FC716 originated from productive hybrids, it should have potential as a source of rhizoctonia-resistant germplasm with high combining ability for sugar yield. Isolation plots had excellent seed set, and FC716 could function as a pollinator or a source population from which to select pollinators, O-types, or CMS females. It was released in 1992 as seed production 911028. FC717 was derived from a cross between FC708 and ACH14. FC708 is a rhizoctonia root rot resistant, monogerm O-type (3) and ACH14 is an American Crystal hybrid. Starting