Antibiosis Resistance of QTL Introgressive Soybean Lines to Common Cutworm (Spodoptera litura Fabricius)

To develop soybean [Glycine max (L.) Merr.] cultivars resistant to common cutworm (CCW; Spodoptera litura Fabricius), it is important to clarify the effects and genetic characteristics of quantitative trait loci (QTLs) for resistance. In a prior study, we detected two QTLs, named CCW-1 and CCW-2, for resistance to CCW in a resistant germplasm, 'Himeshirazu'. Other researchers detected a major QTL for herbivorous insect resistance in PI 229358. Here we constructed near isogenic lines (NILs) of the QTLs via recurrent backcrossing and evaluated the effect of each QTL on antibiosis resistance to CCW. To confirm allelism between CCW-1 and the PI 229358-derived QTL, we did a crossing test. The NILs exhibited significant resistance to CCW compared with the susceptible parent, although the resistance varied between years. The effects of CCW-1 and CCW-2 were similar, and no allelic interaction between them was detected. The crossing test confirmed that CCW-1 and the PI 229358-derived QTL were identical. But the alleles could be different, because the NILs derived from Himeshirazu and PI 229358 showed different levels of resistance.