Mapping and candidate gene analysis of a QTL associated with leaf rolling index on chromosome 6D in bread wheat

1. Leaf rolling is strongly correlating to photosynthesis, transpiration, and respiration. 2. The leaf rolling index QTL, QLRI . cau-6D , was identified by using F 2 and F 2:3 populations. 3. TraesCS6D02G237000 ( TaHDZIV-D1 ) was validated as controlling leaf rolling through knockout and overexpression methods. Leaf rolling is an important morphological trait in wheat ( Triticum aestivum L.), strongly correlating to photosynthesis, transpiration, and respiration, especially in abiotic stress conditions. Identification of quantitative trait loci (QTLs)/genes underling rolling leaf is essential for wheat breeding. In this study, one EMS-induced mutant Y536 was isolated in Nongda3753 background with extreme abaxial rolling leaf. The F 2 and F 2:3 populations derived from a cross between Jing411 and mutant Y536 with contrasting leaf rolling morphology were developed to map locus controlling leaf rolling. A public SSR marker was isolated on chromosome 6DL that held a high linkage level with leaf rolling index (LRI). Quantitative trait locus (QTL) analysis revealed a stable QTL associated with LRI, named QLRI . cau-6D , which explained 7.69 to 10.86% of the total phenotypic variation and had LOD scores ranging from 10.00 to 13.32. TraesCS6D02G237000 ( TaHDZIV-D1 ) was the priority candidate gene according to coding sequence differences between two parents and gene functional annotations. Consistently, knockout of TaHDZIV-A1/B1/D1 in common wheat line ‘JW1’ significantly increased LRI compared to the wild type, as well as overexpression of TaHDZIV-D1 in ‘JW1’ significantly decreased LRI until opposite direction. Moreover, genetic evidence suggested that a dose-dependent manner in TaHDZIV-A1/B1/D1 affects leaf rolling. Collectively, these findings provide a novel and recent insight into the genetic base of leaf rolling in common wheat.