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Subject:
From:
Dave Cushman <[log in to unmask]>
Reply To:
Informed Discussion of Beekeeping Issues and Bee Biology <[log in to unmask]>
Date:
Sat, 7 Oct 2006 15:37:23 +0200
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Hi Joe & all

> But how do you define brood viability diagnostically, in terms that would 
> be useful to the average beekeeper?

If I am not careful here, I will be accused of 'playing with words'. It 
is not so much that high brood viability is a good thing, but that the 
lack of poor brood viability shows that there is an adequate number of 
alleles.

> I mean, what dose it tell you about what’s going on in your queen breeding?

Not much, but if brood viability is low, you should at least be looking 
for the reason why.

> Would it be fair to say that high brood viability would suggest an 
> adequate breeding population and genetic variance?  

You are trying to imply far more than brood viability on it's own can show.

> Would it also suggest  
> a high level of polyandry? 

Absolutely not, polyandry (mating frequency) is the number of drones 
involved in the mating of one queen, it has no bearing whatsoever on the 
genetics of the drones involved.

If those drones are in themselves very variable, but all have a 
particular allele at the sex locus, then as far as that location is 
concerned there is no choice other than the allele that is represented. 
No matter how many drones that exhibit this allele are used in the 
mating the result is still 50% diploid drones.

> I want to focus on in my breeding, selecting for high 
> polyandry.

The degree of polyandry is racially linked, OK there are variations 
about a mean for each race. But using brood viability as a tool is not 
going to tell you the numbers of matings. US bees are heavily focussed 
on Italian bees which have very low mating frequencies, if you do find a 
method of indicating the number of matings and use it as a selection 
tool, you must be wary that you are not inadvertently selecting for AHB 
characteristics, because high mating frequencies are associated with 
African races.

>  I was experiencing low brood viability in some of my stock, 
> but probably wrongly assumed it was the price I was paying for varroa 
> resistance.

Look for some sort of 'bottleneck' or common ancestry in your stocks, 
select away from poor brood viability where it occurs.

 > I discover that ferals that I captured from
 > an ’undisclosed location’ all exhibit 98 to 100% brood viability.
....
 > which caused me to eliminate many of the other swarms I was
 > assessing that season for under performing.

This is probably your bottleneck, you have effectively eliminated the 
background colonies that were delivering the drones with the variability 
of alleles needed... What you should have done is to raise queens from 
those colonies that you considered 'good' and allow them to mate with 
all of the colonies available, then do further selection.

Don't get hung up on brood viability, it will never tell you anything 
positive, only tell you that there is something wrong when it gets low, 
but it does not tell you 'what' is wrong.


Regards & Best 73s, Dave Cushman, G8MZY
http://website.lineone.net/~dave.cushman or http://www.dave-cushman.net
Short FallBack M/c, Build 6.02/3.1 (stable)

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