Pyramiding rag 3, rag 1b, rag 4, and rag 1c Aphid‐Resistant Genes in Soybean Germplasm

The soybean aphid, Aphis glycines , poses a significant threat to soybean [ Glycine max (L.) Merr.]. Use of resistant cultivars is one of the most effective control tactics. Pyramiding multiple resistance genes has great potential to provide durable resistance to soybean aphids. The objectives of this study were to evaluate soybean aphid damage on soybean lines containing individual or a combination of rag 3, rag 4, rag 1b, and rag 1c aphid‐resistant genes, and to identify the genetic interactions of these loci in the greenhouse and field conditions. A breeding population derived from a cross between advanced breeding lines, E08907 with rag 3 and rag 1b from PI 567598B and E09907 with rag 4 and rag 1c from PI 567541B, was evaluated for aphid resistance in four trials in the field and greenhouse. Single nucleotide polymorphism (SNP) markers linked to these genes were used for selection of 12 combinations of resistant genes. Lines with rag 3 or rag 1c alone or a combination of these genes confer a significant level of resistance. Additionally, additive × additive interaction between rag 3 and rag 1c was detected. Lines with rag 4 or rag 1b had lower levels of resistance in the greenhouse and field studies, and their combination ( rag 4 +rag 1b ) is the least effective against soybean aphids.