On Sat, 6 Oct 2007 18:48:54 EDT, Chris Slade <[log in to unmask]> wrote:

>Can you suggest which particular genetically inheritable characteristics
>might make a strain of honeybee less susceptible to nosema?

There have been a number of studies on this issue, most of the work was done
in New Zealand on caged bees from colonies of different racial types. The NZ
work suggests that differences in bee longveity in cages differs by race,
but the relative decline in longevity when bees are infected with nosema is
the same among races - suggesting there is no basis for breeding.  They
tested an older hypothesis that the levels of the enzyme chymosin were
higher among bees that had high longevity despite being infected, but could
not find enough evidence to support it.

Rinderer, Collins and Brown determined that heritable variation in bee
longevity was strongly correlated to increased longevity in the presence of
N. apis.  In the Louisiana population they were making their estimates from
heritability for longevity was estimated to be 0.32, which I understand to
mean that 32% of the variation they observed in longevity was additively
genetic - if an estimate was 1.0 (it never is) then every time you select a
good breeder, all its progeny will express the same good qualities.  They
concluded that "these data suggest longevity would respond to selection and
that correlated responses... to N. apis would probably be favorable".

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