QTL mapping for seedling morphology under drought stress in wheat cross synthetic (W7984)/Opata Maria Khalid 1 , Alvina Gul 1,2 , Rabia Amir 1 , Mohsin Ali 3 , Fakiha Afzal 1 , Umar Masood Quraishi 4 , Zubair Ahmed 5 and Awais Rasheed 3,6 * 1 Atta-ur-Rehman School of Applied Biosciences (ASAB), National University of Science and Technology (NUST), Islamabad, Pakistan, 2 School of Integrative Plant Science, Cornell University, Ithaca, NY 14850, USA, 3 Institute of Crop Sciences, National Wheat Improvement Center, Chinese Academy of Agricultural Sciences (CAAS), 12 Zhongguancun South Street, Beijing 100081, China, 4 Department of Plant Sciences, Quaid-i-Azam University Islamabad 66000, Pakistan, 5 Crop Science Institute, National Agricultural Research Centre, Islamabad, Pakistan and 6 International Maize and Wheat Improvement Center (CIMMYT), c/o CAAS, 12 Zhongguancun South Street, Beijing 100081, China Received 19 September 2017; Accepted 19 January 2018 Abstract Drought stress ‘particularly at seedling stage’ causes morpho-physiological differences in wheat which are crucial for its survival and adaptability. In the present study, 209 recombinant inbred lines (RILs) from synthetic wheat (W7984)× ‘Opata’ (also known as SynOpRIL) population were in- vestigated under well-watered and water-limited conditions to identify quantitative trait loci (QTL) for morphological traits at seedling stage. Analysis of variance revealed significant differences (P < 0.01) among RILs, and water treatments for all traits with moderate to high broad sense herit- ability. Pearson’s coefficient of correlation revealed positive correlation among all traits except dry root weight that showed poor correlation with fresh shoot weight (FSW) under water-limited con- ditions. A high-density linkage map was constructed with 2639 genotyping-by-sequencing markers and covering 5047 cM with an average marker density of 2 markers/cM. Composite interval map- ping identified 16 QTL distributed over nine chromosomes, of which six were identified under well-watered and 10 in water-limited conditions. These QTL explained from 4 to 59% of the pheno- typic variance. Six QTL were identified on chromosome 7B; three for shoot length under water-lim- ited conditions (QSL.nust-7B) at 64, 104 and 221 cM, two for fresh root weight (QFRW.nust-7B) at 124 and 128 cM, and one for root length (QRL.nust-7B) at 122 cM positions. QFSW.nust-7B ap- peared to be the most significant QTL explaining 59% of the phenotypic variance and also associated with FSW at well-watered conditions. These QTL could serve as target regions for candidate gene discovery and marker-assisted selection in wheat breeding. Keywords: analysis of variance (ANOVA), broad sense heritability, drought, International Triticeae Mapping Initiative (ITMI), Pearson’s correlation, QTL mapping, wheat Introduction In developing countries, 50% of the area under wheat cul- tivation is rainfed, which could be the main reason for severe drought stress (Gupta et al., 2017). Grain yield is a complex trait with strong genotype by environment inter- actions. Grain yield is significantly correlated with seedling traits such as root length (RL), shoot length (SL) and dry root weight (DRW) (El-Rawy and Hassan, 2014). Therefore, adaptive traits less influenced by environment like physiological and seedling emergence traits are tar- geted to understand the genetics of drought adaptability *Corresponding author. E-mail: awais_rasheed@yahoo.com; a.rasheed@cgiar.org © NIAB 2018 ISSN 1479-2621 Plant Genetic Resources; 1–8 doi:10.1017/S1479262118000023 https://www.cambridge.org/core/terms. https://doi.org/10.1017/S1479262118000023 Downloaded from https://www.cambridge.org/core. IP address: 67.249.88.243, on 14 Mar 2018 at 11:30:34, subject to the Cambridge Core terms of use, available at