Characterization of fragrance in sorghum (Sorghum bicolor (L.) Moench) grain and development of a gene-based marker for selection in breeding

Abstract

Fragrance is one of the most important and valued quality characters in sorghum and other foods and attracts a premium price in local and global trade. The allele of the SbBADH2 gene in fragrant sorghum cultivar E228 was characterized. A 1441 bp deletion extending from exon 13 to 15 was found rather than a deletion from exon 12 to 15 as had been reported earlier. This allowed the development and validation of a new perfect PCR-based marker for identification of fragrant sorghum accessions in breeding. The concentration of 2-acetyl-1-pyrroline (2AP) in the grain of this cultivar was estimated to be 6.5 ± 0.4 ppb using headspace solid-phase microextraction (HS-SPME) coupled with GC-MS. Flavor components of fragrant sorghum accession E228 (IC 568489) were analyzed and compared with the non-fragrant M35-1 cultivar. PCA analysis revealed that 2AP, benzothiazole, 2,3,5-trimethylpyridine, (1E)-1-ethylidene-1H-indene, cedrene, 2,4-bis(2-methyl-2-propanyl)phenol, 2-hexyl-1-octanol, and 2-butyl-1-octanol were among 25 compounds that were found in sorghum grain that may be contributing toward the aroma of fragrant sorghum. Proline and methylglyoxal contents were found to be higher in E228 than in M35-1, while SbBADH2 expression in E228 was half that in M35-1, suggesting a similar 2AP biosynthetic mechanism to that found in fragrant rice and soybean.