Mapping and candidate genes associated with saccharification yield in sorghum.

Sorghum (Sorghum bicolor (L.) Moench) is a high-yielding, stress tolerant energy crop for lignocellulosic-based biofuel production. Saccharification is a process by which hydrolytic enzymes break down lignocellulosic materials to fermentable sugars for biofuel production, and mapping and identifying genes underlying saccharification yield is an important first step to genetically improve the plant for higher biofuel productivity. In this study, we used the ICRISAT sorghum mini core germplasm collection and 14 739 single nucleotide polymorphism markers to map saccharification yield. Seven marker loci were associated with saccharification yield and five of these loci were syntenic with regions in the maize genome that contain quantitative trait loci underlying saccharification yield and cell wall component traits. Candidate genes from the seven loci were identified but must be validated, with the most promising candidates being β-tubulin, which determines the orientation of cellulose microfibrils in plant secondary cell walls, and NST1, a master transcription factor controlling secondary cell wall biosynthesis in fibers. Other candidate genes underlying the different saccharification loci included genes that play a role in vascular development and suberin deposition in plants. The identified loci and candidate genes provide information into the factors controlling saccharification yield and may facilitate increasing biofuel production in sorghum.