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Saturday, December 25, 2010

KiwiFruit Canker (PSA) in New Zealand

An outbreak of KiwiFruit canker has recently been discovered in New Zealand.  In fact, genetic studies have shown that we have two varieties.  This disease Pseudomonas syringae pv actinidiae (PSA) has destroyed whole KiwiFruit orchards in Italy and caused much damage elsewhere in the world.  Many of the farmers are blaming New Zealand bio-security for the problem.  I think they should look a little closer to home.  Possibly in the mirror.

The KiwiFruit, otherwise known as the Chinese gooseberry is a fabulous fruit.  Original stocks were brought to New Zealand from China back in 1924 and something about our climate suits it very well.  It has become a major export item and a great help to our balance of payments.  You would think we would guard such an industry with great care.  For instance, you would think that as soon as it was apparent that a serious industry was growing around the production of KiwiFruit, we would stop importing any new biological material.  Even if there were no  known diseases or pests of KiwiFruit, you don't endanger such an industry just because you don't yet know of any diseases.  How much more important is it then to stop the import of biological material when you do know that PSA, for instance, has decimated KiwiFruit orchards overseas.

New Zealand is absolutely fanatical about blocking unwanted pests from getting into the country as we should be.  We are far enough away from the rest of the world to isolate us from many of the worlds pests.  If we can stop people bringing biological material into the country, we are reasonably safe.   So why did we not do this in the case of KiwiFruit. I think it must have been a combination of greed, complacency based on familiarity and a lack of foresight.

We have been bringing in KiwiFruit root stock, scions and pollen ever since the industry started and before.  One would  expect a country like New Zealand we would institute the very latest protective techniques.  For instance, if we had need of the genetic characteristics of certain root stock or scions we could have brought them in via plant tissue culture.

In tissue culture, you take minuscule pieces of the desired plant and grow it on agar and later transfer it to soil, producing a whole plant.  During the process, various techniques are used to free the material from bacteria and viruses.  Two of the uses of tissue culture listed by Wikipedia are:
  • The production of plants in sterile containers that allows them to be moved with greatly reduced chances of transmitting diseases, pests, and pathogens.
  • To clean particular plant of viral and other infections and to quickly multiply these plants as 'cleaned stock' for horticulture and agriculture  

Of course, this technique is much more expensive than simply bringing in root stock or grafting wood (scions) from overseas.

Another technique one would have expected to be used is as soon as it became available is genetic testing.  This has only been possible over, arguably, the last decade or two.  When used it will detect if there is any genetic material in imports in a tissue culture other than the KiwiFruit itself.  In other words it can detect bacteria and viruses.  Used in combination with tissue culture, one can be almost certain that no unwanted 'bugs' are coming in with new genetic material.

The really unforgivable import, though, is pollen.  I suppose it must be cheaper to produce pollen overseas than in New Zealand and if you only grow female plants in your orchard you need to artificially pollinate them.  No space is wasted with non producing male plants.  We could have grown orchards here of only male plants and produced our own pollen or we could have inter-planted male plants amongst the female plants.  Instead, we imported pollen from overseas.  I can just hear the industry saying "but we have no indication that pollen carries PSA or any other disease".  For the love of mike, you don't endanger a whole industry because of negative evidence - because you haven't yet found disease organisms in pollen.  This was complacency based on the fact that we had got away with it for a while and the pure greed of farmers wanting to make a little more profit. Have a look in the mirror, guys.

 I wonder  how many other agricultural industries are following a similar course.  How many other industries are importing biological material rather than going through the more expensive but far safer system of plant tissue culture and genetic testing.  We are very strict on individuals coming through our air ports and well we should be.  Why do we not apply the same or more stringent standards to businesses.  Our agricultural industries are far too important to allow this to continue.


Anonymous said...

i agree with this, but to blame the pollen is the obvious way but i dont think the only vector it could have entered the country.
Zespri should be taking a long hard look at themselves too, taking grower groups to italy to look at the psa and the damage it does-come on! idiots!

William Hughes-Games said...

From the Author
Pollen could very well be completely innocent of introducing PSA into New Zealand. At the same time, as we were being very tough on air passengers that had fruit, vegetables of honey in their baggage, we were allowing root stock and scions to come in for all over the place (and Pollen). How incredible to endanger a huge industry like this and not insist that pollen be produced in New Zealand and that any vegetative material be imported through tissue culture. In how many other industries are we unaware of any known problem so we allow the import of such material