Frogeye Leaf Spot (FLS) is a soybean disease caused by the fungus Cercospora sojina. It is distinctly signified by red-brown circular lesions on the leaves that can move to the stems, pods, and seeds in severe infections. QoI inhibitor fungicides had been priorly used to control C. sojina, but resistance was quickly developed. Without adequate control, yield can be reduced to 40% when environmental conditions are conducive. Therefore, genetic host resistance is key to managing the disease. To this end, the ‘Forrest’ by ‘Williams 82’ and the ‘Flyer’ by ‘Hartwig’ soybean populations were screened in the greenhouse for FLS resistance and genotyped using the BARCSoySNP6K BeadChip array. The Rcs15-01 and Rcs15-02 were identified in the Forrest by Williams 82 population on chromosomes (Chr.) 6 and 11, respectively, whereas Rcs15-03 was identified on Chr. 6 in the Flyer by Hartwig population. Although Rcs15-01 and Rcs15-03 were previously mapped on Chr. 6 in the same disease resistance gene-rich region near Satt079, Rcs15-02 was identified as a novel QTL. Overall, our data will help breeders implement FLS resistance into high-yielding lines quickly and efficiently using marker-assisted selection.

Keywords: Frogeye Leaf Spot, Cercospora sojina, quantitative trait loci, marker assisted selection, disease resistance.