The effects of a QTL for root development under hypoxia on yield of soybean exposed to 7-day waterlogging at seedling stage

In humid parts of the world, waterlogging is a major environmental stress limiting the yield of soybean and its root development is an important indicator of tolerance. Recently, quantitative trait loci (QTLs) for this trait were detected on the chromosome 12 of soybean through the analyses of recombinant inbred lines (RILs) developed from a cross between a hypoxia-sensitive cultivar, Tachinagaha, and a tolerant landrace, Iyodaizu. In this study, in order to get a detailed understanding of these QTLs, NIL-9-4-5, a near-isogenic line (NIL), was selected from Tachinagaha/Iyodaizu BC6F2 population through marker assisted selection (MAS). NIL-9-4-5 was then tested for yield performance under waterlogging conditions exposed at the seedling stage. The test was conducted in a greenhouse in 2015 and 2018 at the Experimental Farm of Kyushu University, Fukuoka, Japan. Soybean plants were grown in pots containing loam soil. From six days after germination, seedlings were grown for 7 days under two treatments: drained (control) and waterlogging conditions. Pots were kept in containers where the water level was maintained at 2.0 cm depth from bottom in the control and at 2.0 cm above the soil surface in waterlogged condition. Experimental results consistently showed that seed yields of both Iyodaizu and NIL-9-4-5 were not reduced under waterlogging. Compared to Tachinagaha, NIL-9-4-5 showed higher root development and increased seed yield under waterlogging. These indicate that the tested QTLs are able to increase yield by stimulating root development under waterlogging.