Sweet versus grain sorghum: Differential sugar transport and accumulation are linked with vascular bundle architecture

Sorghum (Sorghum bicolor L. Moench) is globally produced as a source of food, fiber, feed, and fuel. Sweet and
grain sorghums differ in a number of important traits, including biomass production, stem sugar and juice
accumulation. In this study, a sweet (KIT1) and a grain (Razinieh) genotype of sorghum were used to investigate
major differences between sweet and grain sorghum in terms of stem-sugar accumulation. Differences in stem
component traits such as internodes, stem anatomy, but also transcripts of key sucrose transporter genes and
their response to salt stress were compared. While internodal traits were similar, differences on anatomical level
were observed in internodes. Sugar accumulation was highest in the central internodes in both genotypes.
However, phloem to xylem cross areas in internodes was correlated with the amount of sugar stored in stem.
Sugar accumulation increased significantly under salinity in both genotypes. The expression of sugar-transporter
genes SbSUT1, SbSUT2, and SbSUT6 was higher in the leaves of KIT1 under normal conditions, but significantly
increased in the stem of KIT1 under salinity stress. ... mehrNevertheless, transcriptional levels of SbSUT genes could not
account for the big difference of sugar accumulation in stems between both genotypes. Thus, in addition to
anatomical differences, additional (molecular) factors might regulate sugar accumulation in the stem.