Deep-frozen seed banks around the world exist so that farming could restart after a catastrophic war, climate collapse or natural disaster. Researchers at the Australian Grains Genebank have now raised a worrying question about how long the seeds of tropical crops actually last in them. Their one clear piece of good news: after roughly 45 years in storage, 90 per cent of mung bean seed still germinates well.

The team tested the viability of a recently examined batch of stored seed. Common beans proved the shortest-lived, and pigeon pea seed germinated least of all. After an average of 96 years in storage, only four batches retained germination rates above 85 per cent.

The long-held assumption was that frozen seed stays good for centuries. The new results overturn it: the viability of many seeds dropped below 85 per cent within just 20 to 40 years.

Lead researcher and seed specialist Katherine Baum said such rare, long-term tests can be risky and that gene banks should from now on test their seed at regular intervals; better data-sharing would make it easier to conserve plant genetic resources. Norway's famous 'doomsday vault' also holds many crop varieties, but depositing seed is not enough — it must be looked after for decades.

Germination in a laboratory is no guarantee that a seed will grow into a full plant, which requires many further steps, so the scientists are reluctant to treat the results as a complete measure of success. They do expect the new data to improve future models and to play an important part in preserving the genetic diversity of plant species.

The resilience of mung bean matters for a country like Bangladesh, where pulses serve both food security and soil fertility, and where the same question — how often the native varieties held in the national gene bank are tested — applies just as much.

Source: Prothom Alo