Sorghum (Sorghum bicolor (L.) Moench), a C4 African originated grass, ranks 5th most important crop worldwide, feeding over 500 million people in tropical regions as it withstands a wide panel of biotic and abiotic stresses.
The small and simple diploid genome of sorghum was elected as the third plant for sequencing in 2009 promoting it as a C4 model plant.

Among the very diverse genetic resources available for sorghum, sweet sorghum
plants; amassing large quantities of juice-rich and sugar-rich stem, grain and vegetative biomass; have been enlightened as bioenergy crop as it can produced from a single plant food, feed and fuel.

Sweet sorghum has gained interest in Europe to replace maize, for biogas and bioenergy productions, but this versatile crop is sensitive to chilling temperatures and little breeding efforts have been done toward its cold acclimation.
The state-of-art of using quantitative genetic to study cold tolerance has only focused on improving chilling tolerance at early-developmental stages.

In this PhD study we intended to understand the effect of chilling temperatures and long photoperiod on bioenergy-related traits on sorghum adult plants grown under field conditions in Denmark using a panel of genetic and genomic tools.

A large bi-parental QTL mapping study was carried out by using several mapping populations progenies, derived from a cross between a sweet and grain sorghum and they were grown and phenotyped in China and Denmark. The genetic map used for this bi-parental QTL study is a novel map that we constructed using a new
type of molecular markers, exploiting presence absence structural variations uncovered from re-sequencing data.

Using a diversity panel, mainly composed of sweet sorghum accessions, grown in Denmark and phenotyped for bioenergy related traits, we conducted a genome-wide-association-study using a panel of SNPs, InDeLs and large PAVs molecular markers. The genome-wide-association-study study revealed 34 marker-trait-associations mostly concordant with our previous results from the bi-parental QTL mapping study and we identified few candidates’ genes that could be responsible for bioenergy traits under Nordic agro-climatic conditions.