Investigating variations in longevity

Genebanks rely on the ability of seeds to go into an induced latent state when they are dried and cooled. Therefore in genebank storage, seeds must be stored at low temperatures and low moisture content to prevent them from aging.

By contrast, scientists investigating seed longevity deliberately place seeds under conditions that will accelerate the aging process. This allows the scientists to explore processes that normally take decades or even centuries, within a realistic timeframe for a scientific experiment. They subject seeds to conditions of high temperature and humidity, which are described variously as ‘experimental storage’ or ‘accelerated aging’.

Figure 10 (below) shows results from the IRRI experiment described on the previous page. The box covers the 25th to 75th percentiles. The green line across the box is the median; the red line is the mean longevity. The whiskers show the 5th and 95th percentile.

Figure 10: variation in longevity in Indica rice

These data show that there is a lot of variation in longevity, even within one subspecies, Oryza sativa Indica. The mean and median p₅₀ are less than half the maximum longevity shown by a few exceptional individuals, and the box for the 25th to 75th percentiles is somewhat skewed towards the minimum longevity, suggesting there might be scope for improvement.

By working with just one variant of rice, there should be fewer alleles to consider, rather than having to worry about the entire genome of the whole species. However, the variation even within this single variety group of rice underlines how much there is to investigate about the genetic basis of seed longevity.