QTL Mapping for Biomass and Seed-Related Traits in Sweet Sorghum [Sorghum Bicolor (L.) Moench]

Biomass and seed-related traits are one of the most important agronomic traits in sweet sorghum; nonetheless, the molecular mechanisms that regulate these characteristics are incompletely understood. For this reason, the aim of this study was to map QTL controlling biomass and seed-related traits from SNPs discovered by double-digest restriction-site associated DNA sequencing (ddRAD-seq). 175 F₃ plants derived from the cross between sweet sorghum cv. ‘Erdurmus’ and grain sorghum cv. ‘Ogretmenoglu’ were phenotyped in two different environments. A total of 16 QTL were identified; three major QTL (qSH1.1, qSH7.1, and qSH9.1) for stem height (SH), three major QTL (qSD1.1, qSD1.2, and qSD9.1) for stem diameter (SD), three major QTL (qNN1.1, qNN7.1, and qNN9.1) for node number (NN), two major QTL (qNL7.1 and qNL9.1) for the number of leaves (NL), one major QTL (qGWP9.1) for grain weight per panicle (GWP), and one major (qSC4.1) with three minor QTL (qSC2.1, qSC2.2, and qSC4.2) for seed color (SC). The highest percentage variance explained (PVE) was recorded for SH with the value of 37.0. Significant QTL relationships with biomass and seed-related traits were identified on five chromosomes and two significant hotspots on chromosomes 7 and 9. Seven QTL clusters (qNN1.1/qSH1.1, qNN7.1/qSH7.1/qNL7.1, qNN7.1/qSH7.1, qSD9.1/qNN9.1, qSD9.1/qGWP9.1, qSD9.1/qNN9.1/qSH9.1 and qSD9.1/qNN9.1/qGWP9.1) for SH, NN, NL, SD, and GWP traits were detected on chromosomes 1, 7, and 9. Moreover, three novel QTL were identified associated with NL and SC. The findings in this work should be beneficial for molecular breeding programs to increase biomass and seed-related traits in sweet sorghum.