Multiple mutations in BADH2 gene reveal the novel fragrance allele in indica rice (Oryza sativa L.).

The aroma in rice is the most appreciable quality trait, controlled by the loss of function of the betaine aldehyde dehydrogenase 2 (BADH2) gene. In the present study, indica rice cultivars (basmati, nonbasmati aromatic, and nonaromatic) were screened to explore allelic differences in the BADH2 gene using two functional markers (badh2-p-5'UTR and FMbadh2-E7). Notably, the results of the present mutational analysis showed that both markers confirmed a different mutation in indica rice cultivars than earlier reported japonica accessions. It was found that there is 250-bp deletion in the promoter region of aromatic Kagesali and Kalakrishna as compared to nonaromatic Kolamb. The results of FMbadh2-E7 showed 8-bp deletion and six SNPs in exon 7 of the Kalakrishna cultivar. Interestingly, the nonbasmati aromatic Lalbhat rice cultivar did not harbour any reported mutation and showed a novel BADH2 allele carrying 1-bp deletion in exon 7. Among the selected aromatic rice cultivars, eight cultivars showed mutation in the 5' UTR region and interestingly 23 rice cultivars carried the mutation in both 5' UTR and exon 7 of a BADH2 gene. The 2-acetyl-1-pyrroline (2AP) biosynthesis related metabolites, enzyme assay and gene expression supported mutation in BADH2 gene and expression of 2AP in aromatic rice cultivars under study.