A charcterization of sorghum for genes affecting pericarp color and polyphenols

Abstract

Inbred lines, F1 crosses and progeny from F2 populations were utilized to determine if the primary loci which control pericarp color (R, Y, B1, B2 and S) affected tannin presence and concentration differently when they were homozygous as opposed to heterozygous. The semi-automated Modified Vanillin-HCl assay (McDonough et al., 1983) was utilized to chemically assay the grain. When the inbred cultivars (all loci assumed to be homozygous) were chemically assayed, the grain could be separated into the three Groups proposed by Rooney and Miller (1982) based on pericarp genetics. When the F1 crosses (F2seed, loci heterozygous) and F2 progenies (F3seed, loci segregating) were chemically assayed, the grain could be separated into only two Groups: grain which did not contain a pigmented testa (Group I); and grain which did contain a pigmented testa (Group II or Group III). A clear distinction between Group II grain (B1-B1-ss) and Group III grain (B1-B2-S-) was not evident. The agreement between the chemical method of separating grain into three groups, originally proposed by Cummings (1973), and the genetic method of separating sorghum grain into three groups, proposed by Rooney and Miller (1982), was not as clear when loci B1, B2 and S were not homozygous. When the parental cultivars, F1 crosses and F2 progenies were considered as one population and specific genotypes compared (when a testa was present) grain with genotype B2b2 had a higher mean C.E. value than grain with genotype B2B2 . The data were not as convincing but the same phenomena seemed to occur at the B1 locus. Grain with genotype (S-) had a significally higher mean C.E. value than grain with genotype (ss). Genotype RR had a significantly higher mean C.E. value than genotype Rr which had a significantly higher mean C.E. value than rr. Genotype (Y-) had a significantly lower mean C.E. value than genotype (yy). White pericarp color (-- yy) yielded a significantly higher mean C.E. value than red pericarp color (R-Y-) which yielded a significantly higher mean C.E. value than lemon yellow pericarp color (rrY-) . All compaisons involving genes R, Y, and S were made in the presence of a pigmented testa.