Whole genome sequencing of Oryza sativa L. cv. Seeragasamba identifies a new fragrance allele in rice

Fragrance of rice is an important trait that confers a large economic benefit to the farmers who cultivate aromatic rice varieties. Several aromatic rice varieties have limited geographic distribution, and are endowed with variety-specific unique fragrances. BADH2 was identified as a fragrance gene in 2005, and it is essential to identify the fragrance alleles from diverse geographical locations and genetic backgrounds. Seeragasamba is a short-grain aromatic rice variety of the indica type, which is cultivated in a limited area in India. Whole genome sequencing of this variety identified a new badh2 allele (badh2-p) with an 8 bp insertion in the promoter region of the BADH2 gene. When the whole genome sequences of 76 aromatic varieties in the 3000 rice genome project were analyzed, the badh2-p allele was present in 13 varieties (approximately 17%) of both indica and japonica types. In addition, the badh2-p allele was present in 17 varieties that already had the loss-of-function allele, badh2-E7. Taken together, the frequency of badh2-p allele (approximately 40%) was found to be greater than that of the badh2-E7 allele (approximately 34%) among the aromatic rice varieties. Therefore, it is suggested to include badh2-p as a predominant allele when screening for fragrance alleles in aromatic rice varieties.