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Polar bears and resistance to cold

Date Added: 16/12/2016

By Richard Elsdon, Technical Consultant, United Oilseeds

I wonder if, like me, you have been following the ‘Planet Earth’ nature series on BBC1. I am constantly amazed at the way plants, and more particularly animals, have adapted to survive across the earth, especially in some of the most inhospitable areas.

One such animal is the polar bear, which seems to live on little more than fresh air and exercise during the summer, waiting until the sea freezes over so it pursue seals on the ice cap. During the arctic winter, temperatures can plummet to -34 deg C. Add in a little wind chill and we are talking about seriously cold conditions.

Anyone who knows me has come to realise that in order to cope with cold winter weather, I need to be suitably dressed with several layers. I never go on farm without a hat, gloves and scarf readily to hand.  How then, can a warm blooded mammal like a polar bear survive the arctic ice packs, let alone an occasional swim in its sea?  

The answer I understand, is that such animals have developed resistance to the cold.  This has evolved to such an extent, that thermal images of polar bears reveal that the only part of their body which loses any heat at all is their nose. The rest of their body is kept warm by a fur coat with the most fantastic insulating properties.

It was resistance of another kind which was brought to mind last week when I was walking some oilseed rape (suitably attired of course in hats and gloves). One patch was sown to a variety with a resistance rating of “4” to Light Leaf Spot, whilst the other had a resistance rating of “6”. Both had received the same fungicide treatment but it was very evident that there was a large difference in infection rates. The variety rated “6” was clearly less infected.  (Both photos were taken at the same time and at the same patch.)

Variety A with a "4" rating for LLS

Variety B with "6" rating for LLS

At this point, I should admit that some years ago I did not pay much attention to disease ratings as, at the time, the range of available fungicides was capable of controlling any Phoma infection and besides, light leaf spot (LLS) was something that infected oilseed rape in Scotland – right?  Actually, I was wrong! Over the last few years, LLS has become more of a problem in England. We have seen infection climb up the plant and infect developing pods, reducing the yield. At the same time, the range of fungicides in Scotland has shrunk; fluzilazole has gone and while tebuconazole still has a beneficial effect in England, it is no longer effective in Scotland.

We need to look for varieties with a good resistance rating to LLS and Phoma when choosing what variety of OSR to plant. The most important rating is the one for  LLS.

Darwin uncovered the principles of evolution and the idea of the ‘survival of the fittest.’ This process continues across the natural world and seed breeders are employing this same process by selecting varieties with increased disease resistance.  In time this resistance will increase, but probably not as quickly as we would like.  One thing is certain, this process is vital, as I believe fungicides are not a long term answer.   Built-in resistance, as any polar bear will tell you, is the key to survival. 

Readers of this blog are eligible to claim Basis Points using PD/55370/1617/g (1 point)

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