Nested Association Mapping of Agroclimatic Traits in Sorghum

Sorghum (Sorghum bicolor L. Moench) is resilient to semi-arid climatic conditions and is of growing interest for its physiological and morphological adaptation abilities. Crop yield depends first on efficient photosynthesis which is determined by light interception capacity and leaf architecture, as well as efficient allocation of resources to grain fill. As adaptive trait differentiation is historically related with population structure, both statistical effects are confounded and previous association studies using diversity panels resulted in many false positives. To circumvent this problems and decipher the architecture of complex adaptive traits, a NAM population was developed from the crosses of 10 diverse lines with the common parent Tx430 (n = 2,400). The RILs were phenotyped for leaf width, leaf angle, stem width and panicle architecture in two contrasting environments, one semi-arid in Western Kansas and one humid continental in Eastern Kansas, United States. Significant phenotypic variations were observed within and among families as well as transgressive segregation. Preliminary association studies were carried out using 100 000 GBS markers that revealed high resolution QTLs with some new putative candidate genes underneath.

Keywords: adaptive traits, association studies, Sorghum, Nested Association Mapping, Genotyping By Sequencing.