Tomatoes ‘silenced’ to remain fresh

[NEW DELHI] Indian scientists have genetically engineered tomatoes to help them stay fresh for a month longer than they normally would.

Asis Datta and his colleagues at the National Institute of Plant Genome Research (NIPGR) in Delhi identified and suppressed two enzymes that promote ripening to achieve results which have been published in the 9 February issue of Proceedings of the National Academy of Sciences (PNAS).

The two enzymes, ‘alpha-man’ (alpha-mannosidase) and ‘beta hex’ (beta delta N-acetylhexosaminidase), are specifically linked to fruit softening that happens during ripening. Excessive softening accounts for 40 per cent of fruit losses in India.

The scientists ‘silenced’ or suppressed expression of the genes that code for the two enzymes. Their genetically engineered (GE) tomatoes were "2.5 times firmer" than conventional tomatoes.

GE tomatoes retain their texture and firmness for upto 45 days, compared to conventional ones that start shrinking after 15 days. They grow and mature in the same way as normal tomato plants, according to Datta and his colleagues.

Similar manipulation of enzymes involved in ripening could be applied to other fruits such as mango and papaya to extend their shelf life, they say.

Datta, professor emeritus at NIPGR, who led the research team, told SciDev.Net that his team will next conduct larger-scale open field trials, followed by multi-location trials before seeking clearance for commercial cultivation from India’s regulatory authorities. The entire process is expected to take two years.

But Datta is confident about the enormous potential application of his technology not just for India but also other developing countries that suffer huge crop losses due to lack of adequate facilities for storage as well as transport from remote farming areas to urban centres.

He also points out that there are fewer safety issues involved since the genetic engineering does not involve adding foreign genetic material as in the case of India’s genetically engineered ‘Bt brinjal’ that contains genes from the soil bacterium Bacillus thurgiensis to confer resistance to pests.

Datta adds that India’s decision last week (9 February) to halt cultivation of genetically modified brinjal (aubergine) until scientists and public are convinced about its safety (see India says no – for now – to first GM vegetable) "will not cast a shadow" on the fate on GM tomato.