Sweet success

In a commendable feat, scientists last week announced the sequencing of sugarcane genome. Belonging to the perennial grass family, sugarcane was one of the last crop plants to be genome-mapped. In comparison, the rice genome was cracked nearly 14 years ago, followed by many other important agricultural crops. It wasn’t that sugarcane — which yields 80 per cent of sugar consumed globally — wasn’t on scientists’ radar. But its genome was too complex and cracking it with conventional sequencing techniques was rather impossible. It required some ingenious thinking. The international team of geneticists led by French institute CIRAD — which mapped the cane genome — did exactly that. A work carried out at CIRAD 20 years ago had shown that genomes of sugarcane and sorghum, a plant which was sequenced many years ago, share large fragments with numerous genes in the same order. Armed with this knowledge, they devised a way to use the sorghum genome as a template to select sugarcane chromosome fragments to sequence, leading to the first-ever sugarcane reference genome.

Now that its reference genome is created, sugarcane breeding would be able to enter the age of molecular biology. The newly-acquired insights into sugarcane genome can help develop new molecular screening techniques that could hasten field trials of newer varieties. More importantly, the reference sequence can come in handy in analysing and comparing variations between various sugarcane varieties more effectively. It can quickly identify, using molecular markers or by sequencing, whether a species has picked up a desired trait. This in turn can supplement field trials leading to shortening the time required for getting a new variety to the field. Similarly, it is well known that characteristics that contribute to improving a variety rely on the combination of several genes inherited. If scientists can identify genes associated with important agronomic traits, such as yield, drought resistance and ability to withstand pest attacks, these traits can easily be transferred to commercial varieties. Sugarcane is a known water-guzzling crop. If genetic sequences linked to enduring water stress are known, breeders can find a way to incorporate them in their breeding programmes to develop varieties that require lesser water. Similarly, the theoretical limit on the sucrose content of sugarcane is currently around 25 per cent. If breeders can breach this limit, they can raise varieties that are better yielding.

India doesn’t currently allow GM food crops. Brazil, which has the largest area in the world under sugarcane, recently allowed commercial cultivation of the world’s first GM sugarcane. India needs to clarify its stance on GM food crops if it wishes to reap the benefit of such advances.

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