Fragrance in some varieties of rice (Oryza sativa) like Basmati , Jasmine is considered to be one of most important trait of the grains, which finally determines the market price. Scientists trying to find out the genetic origin of fragrance in these crops zeroed on a betaine aldehyde dehydrogenase gene, BADH2, present of 8th chromosome, to be associated with the fragrant phenotype. However the origin and evolution of the betaine aldehyde dehydrogenase gene (BADH2) remained unclear. O. sativa consists of two major varietal groups, Indica and Japonica.

To unravel this mystery Michael Kovach et al, sequenced the gene and a large flanking region in 242 different rice types and shown that that fragrance originated in the Japonica varietal group, not Indica as previously thought.The authors also uncovered eight new alleles of BADH2 and found that the varieties carrying these alleles clustered in specific geographic regions across Asia.

The complete results of the work is published in early online edition of PNAS journal. Interestingly, two of the fragrant cultivars in their study lacked any mutations in the BADH2 gene that would be predicted to cause fragrance, indicating that additional genes might be responsible for aroma in some rice species.

Reference:
“The origin and evolution of fragrance in rice (Oryza sativa L.)”
Michael J. Kovach, Mariafe N. Calingacion, Melissa A. Fitzgerald, and Susan R. McCouch
PNAS -Early online edition

Image Credit: Wikimedia commons

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