Near-isogenic lines of soybean confirm a QTL for seed waterlogging tolerance at different temperatures

Climate change is predicted to increase the probability of soil waterlogging due to severe rainfall, causing significant damage to soybean at the germination stage. Germination under waterlogging is also greatly influenced by temperature. To clarify the variation in germination responses of soybean genotypes to waterlogging at different temperatures, the seeds of 15 soybean genotypes were treated by soaking for 2 days at four temperatures: 21 degrees C, 23 degrees C, 25 degrees C, 27 degrees C and 29 degrees C. Differences in the germination rate (GR) and normal seedling rate (NSR) were observed among soybean genotypes after soaking treatments regardless of the temperature. Among the examined genotypes, Iyodaizu was classified as waterlogging tolerant at the germination stage, and Tachinagaha was classified as sensitive. Interestingly, through the analyses of recombinant inbred lines (RILs) developed from a cross between Tachinagaha and Iyodaizu, quantitative trait loci (QTLs) for root development under hypoxia at the seedling stage of soybean were detected on chromosome 12 (Chr.12).We investigated whether the candidate QTL region for root development is involved in seed waterlogging tolerance by using a near-isogenic line (NIL), NIL-9-4-5. Interestingly, under soaking treatment, the GR and NSR of NIL-9-4-5, carrying the candidate QTL region, was nearly the same as that of Iyodaizu and was significantly higher than that of Tachinagaha. These results may indicate that the candidate QTL region for root development under hypoxia at the seedling stage located on Chr.12 contributes to the seed waterlogging tolerance of soybean plants at the germination stage.