Opium poppies, the source of illicit heroin, are also important for producing medical painkillers such as morphine and codeine, along with noscapine, which has been used for decades as a cough suppressant.

More recently, researchers have found noscapine is also a potent anti-cancer agent, prompting clinical tests into its role in fighting blood cancer.

The discovery that a cluster of 10 genes is responsible for the synthesis of noscapine inside the poppies means plant breeders can now develop high-yielding varieties. It may also help scientists in future produce the drug in factories.

The findings by researchers at the University of York and GlaxoSmithKline were published on Thursday in the journal Science.

British-based GSK is a leading producer of opium-based ingredients, supplying around 20 percent of the world's medicinal opiate needs from poppies grown by farmers in Tasmania.

The fact that all the genes associated with noscapine are clustered together makes life much easier for plant breeders who can use the information to develop high-yielding commercial noscapine poppies.

In contrast to illegal opium production in countries like Afghanistan, where harvesting is done by hand by lancing poppy heads, commercial pharmaceutical production is highly mechanized, with farmers using modern combine harvesters.

That makes commercial poppy cultivation a cost-effective process, even though most medicines today are produced by chemical synthesis or biotechnology.

"The poppy plant is very efficient at producing these compounds," said Ian Graham, director of the Centre for Novel Agricultural Products at York.

Working back from a strain of poppies producing high levels of noscapine, Graham and colleagues followed the trail of genes linked to the chemical to home in on the cluster of 10 specific genes central to production of the compound.

The cluster of genes, all of which are inherited together, is the most complex ever found in plants.

Noscapine was first discovered in the early 19th century and has been used to suppress coughs since the 1950s, but interest in the compound has grown since 1998 when scientists demonstrated that it acts as a potent anti-tumor agent.

It functions in a similar way to Taxol, a cancer drug originally isolated from the bark of the Pacific yew tree and commercialized by Bristol-Myers Squibb.

Cougar Biotechnology, now part of Johnson & Johnson, has been studying noscapine as a treatment for multiple myeloma, a type of cancer affecting the plasma cells in bone marrow.

(Reporting by Ben Hirschler; Editing by Will Waterman)

• A Permanent Economic Emergency