Plants defend themselves during attempted invasion of pathogens via induced and systemic acquired resistance mechanisms. One of the important active components of plant defense is the production of low molecular weight antimicrobial compounds called phytoalexins. Sorghum plants produce phytoalexins of the 3-deoxyanthocyanidins type as a rapid response to Cochliobolus heterostrophus infection. These compounds have structural similarities with flavan-4-ols; the precursors of the red phlobaphene pigments that accumulate in the developing kernels of sorghum. Previous studies suggested that flavan -4-ol might serve as precursors of sorghum 3-deoxyanthocyanidins phytoalexins. Recent studies from our lab indicated that flavan-4-ol biosynthesis is under the control of a Myb transcription factor yellow seed1 (y1). We want to extend this work further and test if the biosynthesis of flavan-4-ol and 3-deoxyanthocyanidins are under a common regulation of y1. The objective of this project was to genetically demonstrate if y1 is required for sorghum phytoalexins by screening F₁₀ recombinant sorghum lines.  The seeds were inoculated with C. heterostrophus and then their responses were compared with standard sorghum stocks that differ in their ability to produce these compounds.  Pure apigeninidin and luteolinidin were used to quantify the induced phytoalexins in sorghum lines under study.  Results of biochemical analysis showing the levels of phytoalexins will be presented.  The results from this study can be used for comparison in future studies on phytoalexin expression of other sorghum lines.

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