Why priming watermelon seeds helps to overcome cold stress

Why on earth would you want to have primed watermelon seed? In general, watermelon germinates quite fast, and the effect of priming appears to be limited. That is, at an optimal temperature of 25°C. And if you have a low total emergence, then priming is probably not the way to go. In that case you need some kind of upgrading to remove the bad, non-germinating seeds.

However, when you germinate watermelon seeds at a suboptimal temperature, priming can be a real asset. One way to express the speed of germination, is by calculating the T50. That stands for the time needed to reach 50% of the final germination. At 25°C, the T50 of primed seeds improves by 0.1 to 0.9 days, but at 20°C the improvement ranges from 0.9 to 2.4 days and at 15°C it is between 1.3 and 7.1 days, measured on 8 seed lots. While at 15°C, several lots of unprimed seed still had a low germination after 12 days, when the test was ended.

When you germinate watermelon seeds at a suboptimal temperature, priming can be a real asset.

But then, why would you want to germinate seeds at a suboptimal temperature? Although the answer may seem odd, it’s because of increasing temperatures. In southern Europe, spring and summer temperatures are getting higher and higher. In order to have a decently developed plant before that occurs, plant raisers are sowing as early as possible. So early that temperatures can still be quite low, but by using primed seed, emergence will still be good.

Although spring and summer in southern Europe are increasingly warmer, it’s cold stress that is becoming more and more of a problem

Seed lot primed with Promotor Watermelon (right) and an unprimed seed lot (left).

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