WHAT鈥檚 yellow, bent and is about to spill all its secrets? Yes, the humble
banana will be the first edible fruit to have its genetic code unravelled.
The first plant genome to be sequenced was the mustard cress Arabidopsis
thaliana. Rice was next, but the companies that sequenced it have been
criticised for not making the data freely available
(快猫短视频, 3 February, p 6).
Now bananas鈥攇enus Musa鈥攁re go. A global consortium of
publicly funded institutes met in Washington DC this week to finalise details.
They plan to have the job done within five years, and will post all the gene
sequences on the Web as soon as they鈥檙e available.
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The Global Musa Genomics Consortium will focus on discoveries that will
benefit the smallholders who grow 85 per cent of the world鈥檚 bananas, mostly for
their own consumption. 鈥淥ne rule of joining the consortium is that any invention
developed through the project and protected [by patent] will be made available
to smallholders through a royalty-free licence,鈥� says Emile Frison, director of
the International Network for the Improvement of Banana and Plantain, the French
charity that is the driving force behind the genome effort.
The sequence could be of great value to breeders and scientists, who have
struggled to overcome the banana鈥檚 weird characteristics. For example, the
classic Cavendish variety exported to Western countries鈥攚hich is thought
to have originated as a natural hybrid thousands of years ago鈥攈as three
sets of chromosomes instead of two and so cannot reproduce sexually.
鈥淗alf the world鈥檚 edible bananas, including the Cavendish, are entirely
sterile, and you can鈥檛 breed them at all,鈥� says Frison. Instead, they are
propagated by taking the plantlets that appear at the base of old banana plants
each year.
Because they have been in evolutionary limbo for thousands of years, the
edible varieties are particularly vulnerable to pests and disease. 鈥淏anana is
one of the most heavily sprayed crops in the world,鈥� says Frison. In Costa Rica,
for example, they spray bananas roughly once a week, compared with four or five
times a year for most other crops.
This is why, instead of sequencing one of the edible varieties, the
consortium will sequence a wild banana from east Asia. This should contain
useful genes that could be added to edible varieties. For instance, a gene that
protects against the black Sigatoka fungus, which ravages plantations, would be
priceless.
But because interbreeding is impossible, genetic modification is the only way
to insert such genes into most commercial varieties. 鈥淭his is one of the few
crops where you could say there鈥檚 a strong justification for using GM,鈥� Frison
says.
The consortium already has funding of $2 million per year, but needs a
further annual $4 million. It hopes to raise this through bodies such as
the US National Science Foundation and the European Union.
鈥淭he establishment of a public research initiative is welcome,鈥� says Antonio
Hill of the development charity Oxfam. But the British-based charity says the
researchers should examine beforehand the socio-economic impacts of new
varieties to ensure they don鈥檛 end up damaging the livelihoods of the very
people they鈥檙e trying to help.
Frison says they won鈥檛 be seeking genes that would make bananas straight. 鈥淚t
would take all the fun out of bananas,鈥� he says. 鈥淭hey鈥檇 be so boring.鈥�