Registration of three near‐isogenic soybean lines carrying the <i>Rcs3</i> allele for frogeye leaf spot resistance

Abstract Soybean [ Glycine max (L.) Merr.] yield can be reduced by 30% or more when infected with frogeye leaf spot (FLS), a fungal disease caused by Cercospora sojina K. Hara. The Rcs3 quantitative trait locus (QTL) provides strong resistance to all races of C. sojina reported in the United States and Brazil. By backcrossing the Rcs3 QTL from the resistant cultivar ‘Davis’ (Reg. no. 56, PI 553039) into the elite cultivars ‘Gordon’, ‘Thomas’, and ‘Wright’, three BC 5 F 2 ‐derived near‐isogenic lines (NILs) were developed: ‘Gordon‐ Rcs3 ’ (Reg. no. GP‐551, PI 708927), ‘Thomas‐ Rcs3 ’ (Reg. no. GP‐553, PI 708929), and ‘Wright‐ Rcs3 ’ (Reg. no. GP‐552, PI 708928). In greenhouse disease assays, these Rcs3 NILs were resistant to five virulent races of C. sojina . In field evaluations, the NILs had similar appearance and agronomic characteristics to their respective recurrent parent. Haplotype analysis indicates that a segment of chromosome 16 harboring the Rcs3 QTL has been introgressed into each NIL. This germplasm will be useful as parents for breeding soybeans resistant to FLS and for future research on FLS and the Rcs3 QTL. These Rcs3 NILs are being released as germplasm by the University of Georgia for breeding and research purposes.