SCREENING FOR GRAIN POLYPHENOL VARIANTS FROM HIGH TANNIN SORGHUM SOMACLONES

Several hundred somaclones established from plants regenerated from em bryogenic callus cultures of six high tannin sorghum lines were screen ed for variants with altered levels of polyphenols in the grain. Grain fi-om over 6000 plants including the R(1) (primary), R(2), and R(3) g enerations were analyzed for total phenols, flavan-4-ols, and proantho cyanidins (condensed tannins). Although many variants which had lost t he ability to synthesize chlorophyll were found, none of the somaclone s tested had lost or greatly reduced the ability to synthesize any of the polyphenols assayed. However, we did observe statistically signifi cant differences in polyphenol concentration between tissue culture-de rived R(1) plants and the parental controls. In the R(2) generation th e proportion of somaclones which differed significantly from the paren ts varied from 47% to 68% depending upon genotype. The average somaclo nal variation rate and somaclonal variant frequency estimated in the t ested population for the three polyphenol characteristics ranged from 37.3% to 40.7% and 5.3% to 7.8%, respectively. Variants with decreased levels of polyphenols were usually epigenetic and reverted back to no rmal levels in subsequent generations, but those with increased levels usually persisted after two meiotic cycles, indicating they are herit able. Variants with polyphenol levels increased up to 80% or decreased by 30% were selected for in the R(3) generation.