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Tuesday , February 2 , 2010
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45 days and still fresh
- In Delhi lab, world’s longest-lasting tomatoes

New Delhi, Feb.1: Refrigerator marketers, looks like you need to change your “farm-fresh” sales pitch.

Plant biologists in India have discovered two previously unknown genes that are involved in fruit ripening and shut them down to create what might be the world’s longest-lasting tomatoes.

The tomatoes developed at the National Institute of Plant Genome Research (NIPGR), New Delhi, can retain their firmness and texture for up to 45 days without refrigeration, compared with ordinary tomatoes that shrink and lose texture in about 15 days.

The researchers at the NIPGR have applied their gene-silencing technology on tomatoes, but they say it may also, in theory, be used to increase the shelf life of mangoes, papayas and bananas.

“We’re not adding new genes into tomatoes -- the shelf life is increased by shutting down two genes that make the fruits go soft,” said Asis Datta, the senior scientist at the NIPGR who led this research.

Datta and his colleagues identified two plant enzymes and their genes — alpha-Man and beta-Hex — that drive fruit ripening. Then they applied a well-known trick called RNA-interference to “silence”, or shut down, the alpha-Man and beta-Hex genes. The results of their experiments will appear tomorrow in the journal Proceedings of the National Academy of Sciences.

The lack of a widespread network of cold-storage facilities and the softening of fruits during transportation leads to the post-harvest loss of nearly 40 per cent of India’s annual produce of fruits and vegetables.

Many research groups, including one at the Indian Agricultural Research Institute, New Delhi, have previously tried to increase shelf life of tomatoes by suppressing various known enzymes involved in the process of ripening.

“But the shelf-life improvements so far have been inadequate -- either from the point of view of softness or texture of the tomatoes,” said Subhra Chakraborty, a team member at the NIPGR.

Scientists who were not associated with the research say it appears promising. “The work is somewhat unique ... the team led by Datta attacked a different ripening pathway,” said Roger Beachy, a leading plant biotechnologist and the director of the National Institute of Food and Agriculture in the US.

“I hope this work is followed up with studies to determine if the technology will help reduce post-harvest losses to other valuable crops and enhance food supply that will help feed a growing population,” Beachy told The Telegraph.

The genetically-modified tomato would have to pass a series of field trials, including animal safety tests, before it can be considered for commercial cultivation. The NIPGR scientists say the process could take three years, perhaps longer.

But scientists caution that applying the gene-silencing strategy to other fruits may be technically challenging.

“Papayas and bananas are candidate targets, but mangoes have resisted all efforts at genetic engineering,” said Kailash Bansal, a scientist at the IARI who has used a similar technique to delay ripening of tomatoes.

The NPIGR achievement comes at a time the government is conducting public consultations on the introduction of a genetically modified brinjal in India. The brinjal has been approved by a scientific panel, but is being opposed by activists.

Datta said he doesn’t expect his tomatoes to run into similar controversy.

“There is no alien gene in these tomatoes — its two genes have been silenced,” he said. The RNA interference technique involves designing special gene sequences that shut down the activity of the target genes — in this case the alpha-Man and beta-Hex.

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