PLANT RESISTANCE Seed Yield of Near-Isogenic Soybean Lines with Introgressed Quantitative Trait Loci Conditioning Resistance to Corn Earworm (Lepidoptera: Noctuidae) and Soybean Looper (Lepidoptera: Noctuidae) from PI 229358

The development of superior soybean, Glycine max (L.) Merr., cultivars exhibiting resistance to insects has beenhindereddue to linkagedrag, a commonphenomenonwhen introgressing alleles from exotic germplasm. Simple-sequence repeat (SSR) markers were used previously to map soybean insect resistance(SIR)quantitative trait loci (QTLs) ina ÔCobbÕ PI229358population, and subsequently used tocreatenear-isogenic lines(NILs)withSIRQTLina ÔBenningÕ geneticbackground.SIRQTLswere mapped on linkage groups (LGs) M (SIRQTL-M), G (SIRQTL-G), and H (SIRQTL-H). The objectives of this study were to 1) evaluate linkage drag for seed yield by using Benning-derived NILs selected for SIRQTL-M, SIRQTL-H, and SIRQTL-G; 2) assess the amount of PI 229358 genome surrounding the SIR QTL in each Benning NIL; and 3) evaluate the individual effects these three QTLs on antibiosis and antixenosis to corn earworm, Helicoverpa zea (Boddie), and soybean looper, Pseudoplusia includens (Walker).Yielddatacollected inÞveenvironments indicatedthata signiÞcantyieldreduction isassociated with SIRQTL-G compared with NILs without SIR QTL. Overall, there was no yield reduction associated with SIRQTL-Mor SIRQTL-H. A signiÞcant antixenosis and antibiosis effectwas detected for SIRQTL-M in insect feeding assays, with no effect detected in antixenosis or antibiosis assays for SIRQTL-G or SIRQTL-Hwithout the presence of PI 229358 alleles at SIRQTL-M. These results support recent Þndings concerning these loci.