Image Analysis for QTL Mapping of Stem Pithiness in Sorghum.

Levels of stem juiciness determine the end-use of sorghum bioenergy feedstocks. For instance, high and low moisture content in the stems is desirable in sweet and biomass ideotypes, respectively, which has direct implications for breeding. Several physiological and abiotic factors affect stem moisture in plants. Pithiness in the stems is a disorder associated with significant yield penalties in sugarcane and bioenergy sorghum. This phenomenon translates in the accumulation of large air space in the parenchyma stem cells; reducing the quality and moisture in the stem. Historically, limited research has focused on understanding the genetic architecture of stem pithiness and its impact on sorghum traits. Herein, image and multi-trait-QTL analysis were combined to identify loci associated with quantitative variation in stem pithiness and moisture content. The phenotyping assays and data analysis will be described briefly. Finally, we present the QTLs detected; and, discuss their effects, consistency, and implications for breeding based on multi-environment trials.