Crossbreeding: New Study Sheds Light On History Of Black Rice

When we think of rice, we usually think of white or brown grains. However, black rice is prized throughout China for its antioxidants. But how did the rice get its color? Researchers took a closer look at the grain's rich history to find out.

Black rice was historically reserved for China's Emperor and regarded as "forbidden." Today, black rice (Oryza sativa) cultivars are found throughout Asia. The color of rice grains is determined by which colored pigments they accumulate, or in terms of white rice, the pigments they fail to attain (in addition to not having because the outer hull has been removed). The color in black rice is a result of anthocyanin pigments, according to a news release. Anthocyanins absorb blue-green light, and reflect red wavelengths. So, for example, pro-anthocyanidins that give wild rice grains their red color are not produced in white rice due to a gene mutation. Scientists have long questioned how these pigments evolved in grains.

Researchers from Japan recently traced the history of anthocyanin pigments, from their molecular origin to their spread in modern-day varieties of rice. After examining the genetic basis for the black color in rice grains, the researcher found the pigments resulted from the rearrangement of a gene know as Kala4.

This gene activates the production of anthocyanins, the release noted. From this, the researchers concluded that this mutation originally occurred in the tropical japonica subspecies of rice and eventually evolved among other varieties through processes of crossbreeding.

"The birth and spread of novel agronomical traits during crop domestication are complex events in plant evolution," Dr. Takeshi Izawa, the study's lead author, said in a statement.

Their findings help better explain the domestication of rice by ancient humans, who would have crossbred rice with preferable traits, such as grain color. Their study was recently published in the journal Plant Cell.

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