Basmati's sweet smell comes from japonica

But, looks can be deceptive. Researchers now show that the signature smell of basmati originated in japonica rice  and not in the white indica rice, to which basmati belongs.  
Globally there are two broad rice varieties  –– japonica and indica. They are different in look, taste and certain chemical contents.

For rice, fragrance is considered as one of the most vital grain qualities. It is a key factor in determining its market price. Aroma is also integral to the identity of basmati, produced in India and Pakistan.

By comparing 242 types of rice lines, researchers found that though the fragrance-causing gene is present in all major varieties, it first evolved in the japonica variety. The findings have been reported in the latest issue of the Proceedings of National Academy of Sciences on Tuesday.

Geneticists Susan R McCouch and her colleagues at International Rice Research Institute (IRRI), Manila and Cornell University, New York investigated into the genetic and geographic origin of fragrance in rice.

They identified an area on the chromosome 8 of the rice, associated with fragrance. Fine mapping and subsequent analysis identified a specific fragrance gene called BADH2 involved in creating a chemical which produces the aroma.

Since over 100 volatile compounds have been detected in fragrant rice varieties, the major compound responsible for the characteristic aroma is called 2AP (2-acetyl-1-pyrroline) which is produced in all parts of the rice plant except the roots.

The chemical, 2AP, has a very low odour threshold, allowing humans to detect it at minute concentrations in field-grown plants or crushed leaf tissue, as well as in the grain before, during and after cooking.

It is believed the BADH2 gene is responsible for the enhanced production of 2AP. The same gene is also responsible for the scent in Thailand’s long grain jasmine rice.

The authors identified two fragrant cultivars which lacked any known alteration in the BADH2 gene, implying that additional genes controlling fragrance may exist in rice.

Other rice researchers are not surprised by the findings. “Basmati rice is genetically close to japonica. So it’s possible that this gene originated in japonica and came later to basmati (indica background),” Swapan Datta, deputy director general (crop science) at Indian Council of Agriculture Research (ICAR) told Deccan Herald.

Can this gene be commercially exploited? Datta said it is possible to transform regular rice without any scent into an aromatic variety by inserting this gene.

DH News Service