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Date: | Sun, 21 May 2023 08:54:19 -0500 |
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... we and Mom Nature working together would fix the trait in no time, as has occurred elsewhere.
Interesting literature review from the same lab touches on the challenges of breeding for resistance, suggesting that a lack of understanding of the mechanism(s) at work may be our biggest hurdle at present:
https://gsejournal.biomedcentral.com/articles/10.1186/s12711-020-00591-1
The choice of traits currently used in selection for resistance derives from observations of naturally-resistant colonies. However, the traits or combination of traits that provide protection to infested colonies have not been empirically determined. Thus, the role of currently used traits towards improving survival remains hypothetical. Determining the role and importance of the suspected traits is limited by the complexity of the experimental designs required. The prerequisites for such tests are honey bee lineages that express different trait combinations at different intensities so that a comparative study can be performed. The multi-year duration of the tests required due to the relatively long generation time and longevity of honey bee colonies and the time required for V. destructor to exert an impact on colony survival add to the challenge. In addition, data on the genetic background of resistance traits to help choose traits for selection are lacking.
And to my knowledge, the only trait that has been found to be ubiquitous in all naturally surviving populations is uncapping-recapping as identified by the work of Dr. S.J Martin.
But, I suspect that resistance is a multi-factorial suite of behaviors combining genetic and possibly epigenetic inputs. A few interesting tid bits on this score from the paper:
As long as the impact of local environment on the ability of the selected traits to limit infestation remains unknown, progress towards surviving stock will likely be limited.
The lack of progress towards the selection of honey bee lineages surviving infestations by V. destructor is probably not due to the generation time of the honey bee, which is short compared to other livestock such as cattle, but is likely due to caveats in selection strategies and knowledge gaps in our understanding of resistance mechanisms.
The literature focusing on resistance traits indicates that several agents can affect their expression. These agents are the parasite itself, other pests and the host via its biological attributes or via the interaction between resistance traits. As a result, only part of the phenotype measured reflects the ability of a colony to defend itself against the parasite.
It is worth noting that heritability might be confounded by epigenetic processes. A genetically inherited trait is indistinguishable from a trait acquired via social learning, when workers have the ability to transmit acquired knowledge across generations: thus, behaviours may be expressed by related workers without a genetic causality.
The likely frequent occurrence of genotype-by-environment interactions indicates that adaptation to local conditions plays a major role in colony survival and restrains the possibility to export resistant colonies to regions with different environments. Because of the lack of initial local adaptation, importing resistant colonies from other regions or environments bears low chances of success, and selecting local stock is recommended.
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