BANANA GENOME SEQUENCE

Scientists have sequenced the complete genome of the banana, an important crop in developing countries that provides a fruit widely enjoyed the world over and is a staple food in some of the poorest parts of the globe.

The draft sequence provided “a crucial stepping-stone for genetic improvement of banana,” observed Angélique D’Hont, a French agricultural research scientist, and colleagues from a number of other countries in a paper that is being published this week in the scientific journal Nature.

The sequence represented, they said, “a major advance in the quest to unravel the complex genetics of this vital crop, whose breeding is particularly challenging.”

Pests and diseases were an “imminent danger” for global banana production. Having access to the entire gene repertoire of the plant held the key to identifying those responsible for disease resistance as well as ones for other important traits such as fruit quality, they added.

The completion of the genome sequence was important for India, the world's largest producer of bananas, according to P. Padmesh of the Jawaharlal Nehru Tropical Botanic Garden and Research Institute near Thiruvananthapuram in Kerala. However, most of the country's production was consumed locally and exports amounted to only 0.5 per cent of the world trade in the fruit.

The potential for export was huge if India could increase its productivity both in terms of quantity and quality, he told The Hindu in an email. As most of the present day cultivated varieties were susceptible to fungal, bacterial and viral diseases, it was necessary to develop disease-resistant varieties.

The international team has sequenced the genome of DH-Pahang (Musa acuminata), a banana popular in south-east Asia and which is able to resist the devastating Panama disease fungus that has been spreading in Asia.

If the genes that provide such resistance could be characterised, they could be transferred to other cultivated varieties, noted Dr. Padmesh.

The genome that has been sequenced ran to 523 million ‘bases,’ the chemical units that make up DNA and encode the genetic information. Transposable elements — the ‘jumping genes’ that can relocate themselves to other places in the genome from time to time — accounted for almost half of those bases.

Bananas that are cultivated, unlike their wild relatives, are seedless and develop without going through a process of pollination, fertilisation and seed production. These domesticated forms are therefore propagated by using a part of the parent plant. As a result, the offspring are genetically similar to the parent. Such similarity can allow disease-causing organisms to rampage through a crop.

The transposable elements in the banana genome therefore provide a major natural source of genetic variation, noted Dr. Padmesh.

SOURCE: The Hindu.