Why are Sarpo spuds a breakthrough?

From David Shaw in blighty North Wales.

There are two reasons why the official scores indicate Sarpo varieties are no better/worse in their official scores. than other varieties.

1) The scores are out of date.  Testing in government laboratories is done before the variety is commercialised - the the case of Sarpo Mira, 2002 and Axona, 2004.  The blight population in UK has changed since then.  New strains have become common and one strain, Blue 13, is particularly virulent and can overcome most of the foliage resistance of high scoring varieties like Lady Balfour, Orla and Setanta.  Blue 13 is not able to overcome the resistance of most of the Sarpo varieties.  Retesting by government labs and and field trials by the likes of Sarvari Research Trust will update resistance scores.  This takes time and money and many of the less popular varieties will not be tested in the near future. 

2) Official scores for foliage blight and for tuber blight are based on a few experiments in the laboratory and are not always a good indication of what happens in the field.  A good example is Axona which is said to be only moderately foliage resistant (0 - 9 score of 6).  In field trials, Axona is still one of the most resistant varieties.  Blight infections spread more quickly on Axona than on Sarpo Mira but only in severe blight conditions does this have an effect on yield.  Incidentally, the scores given sometimes depend on the publication you look at. This may be a copy error.  Sarpo Mira (score of 7 for foliage blight on the Briish Potato Variety Database) is still used as a standard in blight trials throughout Europe and is found to give the highest scores consistantly.

The newer Sarpo varieties are an attempt by the breeders to select potatoes with a range of maturities, skin colour and cooking/taste characteristics, different from the first Sarpos to be introduced (middle maincrop and high dry matter).  The newer ones do have lower scores for foliage blight than Sarpo Mira but in most seasons, with a moderate to low blight pressure, the resistance of these new varieties is adequate and still better than most other so-called blight resistant varieties.

David

Thank you, David. Now I understand. It's a bit frustrating, though, when the only info we can look up is out of date. Disease resistance is important to me because I don't like to use chemicals, and I'm sure I'm not alone in that, so here's hoping the research data gets updated at some point.

Interestingly, I've just had problems with blackleg in my spuds. I had one row of Desiree, one of Sarpo Axona and one of Sante, which is supposed to be a good choice for organic gardening. The entire row of Sante collapsed almost overnight and a few of the Desiree have gone but all the Axona look as strong as ever, although it only scores 6 for blackleg resistance. Next year I think I'll be sticking with the Sarpos

Are there any white skinned Sarpos or are they all red?

after reading the advice on your website which says to remove volunteer plants asap - what if they appear in the middle of your peas for example and digging up the offending potato and plant would destroy your pea plants.would a dose of round up kill the potato ?at the minute i just keep carefuly pulling out the potato stalk.

after reading the advice on your website which says to remove volunteer plants asap - what if they appear in the middle of your peas for example and digging up the offending potato and plant would destroy your pea plants.would a dose of round up kill the potato ?at the minute i just keep carefuly pulling out the potato stalk.

RW,  If you cut off the stem, the buds on the part of the stem remaining will quickly grow.  I would try to pull up the stem or stems to try to get all of them out and, if you are lucky, the seed piece as well.  I guess that Roundup would be tricky to apply amongst the peas and it takes time to kill the plant.  Meantime the blight might develop.

Even if your crop was blighted last year, the chance that volunteers will carry the blight is low.  The real danger is if lots of discarded blighted tubers are dumped in a ditch or similar.  Then the chance gets much higher.

It is not widely known that if you plant 100 blighted tubers, most will not grow but of the ones that do, most or all will be healthy and blight free.

DAvid

thx david, i destroy all foliage and potatoes i wont use anyway, its mainly the volunteer plants that i get , hard to stop them tho as alot of them are from extremely small tubers or ends of tubers that have been chopped off with a spade.

one last question, which of the new maincrop sarpo varities are the waxiest?

 Kifli and the early, Sarpo Una, are the waxiest. Some people like Sarpo Una as an early baker but I don't.  Taste is OK but too wet.
David