# Temporal changes in the viromes of Swedish Varroa-resistant and Varroa-susceptible ho



## Juhani Lunden (Oct 3, 2013)

This is what I have been saying 10 years: varroa resistant bees are resistant to viruses.

https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0206938

16.8.2009
Some observations:

•	the virus tolerance of the bees is an important trait and genetically dependent (2007 I introduced one Italian queen, 3 weeks later there came out wingless bees)


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## Litsinger (Jun 14, 2018)

Juhani Lunden said:


> This is what I have been saying 10 years: varroa resistant bees are resistant to viruses.
> 
> https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0206938


Juhani:

Thank you for sharing this article- a very interesting read. If I interpreted the results correctly, it sounds as if the research ultimately left open the question of whether this virus tolerance is a result of genetics, colony isolation or a complex interaction of the two:

_“Phylogenetic analyses of the assembled virus sequences revealed consistent separation between the MR and MS honeybee populations, although it is unclear whether this is due to pre-existing differences between the viruses in the two populations when they were established, and isolated, or due to virus genetic adaptation towards reduced virulence in the MR population, to promote colony survival.”

“The extent to which these observations on virus titres can explain the difference in colony survival between the two populations is limited. Many other parameters important for colony survival also differ drastically between the two populations, such as colony size and mite reproductive success, making it difficult to gauge the relative importance of the decrease in virus titres for enhanced colony survival.”_

That said, it is interesting to see that the results suggest that the MR colonies responded much more favorably to virus pressure during late season winter bee rearing than did the MS colonies:

_“Overall, there were no major qualitative differences in RNA metagenome composition between the MR and MS honeybee populations: the same type of viruses, bacteria and other parasites were recovered from both populations…”

“These showed that the titres of these viruses were relatively similar for MR and MS colonies during the summer, but diverged as the colonies moved into autumn and started producing winter bees, with the virus titres decreasing strongly in the MR colonies relative to the MS colonies.”_

Thank you again for posting. Have a great week.

Russ


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## enjambres (Jun 30, 2013)

It seems to me that it would easier to breed for viral resistant genetics than for the specific behavior patterns typical of varroa-sensitive lines. Perhaps also more stable from generation to generation.

Nancy


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## Juhani Lunden (Oct 3, 2013)

This incident which woke up my curiosity towards virus resistance happened 2007, just 6 years after starting my breeding program. Makes one think of some other than genetical explanation.

Interesting that the study did not find differences in viruses. It has often been said here on BeeSource, that viruses are likely to change...


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## lharder (Mar 21, 2015)

Very interesting article Juhani. Understanding viral ecology is vitally important. It has been ignored with all the talk about mites. If it was all about mites, then one would see very consistent thresholds for mite levels in the fall that correlate with winter mortality/spring strength. I don't see this so far. Some higher mite hives are very strong in the spring, some lower mite hives die in the winter. I believe much of this is due to variability in virus resistance. Hope to be able to prove it at some point. Its the reason why tf bond systems are superior to just selecting for low mites. You select for virus resistance as well. There is a mite threshold number, but it is higher than most people think. 

But not all viruses everywhere. I believe adaptation to viruses will prove to be a local phenomena. So much bee (and their viruses) movement causes genetic chaos for both bees and viruses resulting in the terrible mite threshold levels associated with big migratory commercial beekeeping.


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