Hi Allen

>The SMR mechanism was not explained, but the method of selection was.


As I remember from his papers there are at least two types.  Remember that
in the Varroa life cycle, a mother lays one male egg and one or more female
ones.  The male does not survive outside the sealed cell.  Females mate with
their brother before the cell is opened.  In one type of SMR, the female
mites are unfertilised, or poorly fertilised - here the mechanism could be
that the male mites do not thrive on these bees and are not as fertile as
they should be.  So, daughter mites do not reproduce as they carry defective
sperm or none at all.  In this type, if colonies are made up experimentally
with an SMR queen but non-SMR workers and their mites, the SMR trait builds
up over a few brood cycles as the mites go through their reproductive cycles
and the old mites that arrived (already fertilised) in the experimental
colony die off.  John Harbo and colleagues also saw SMR expressing in the
first brood cycle in at least one experiment, so this must arise from a
different mechanism.

>Harbo simply pulls out 200 worker pupae that are a little past the eye
>colour stage and examines them for mites.  The SMR bees will have only the
>(prospective) mother mite(s) -- and no offspring attached.  An obvious


Allen - the experiments I read about were all with worker brood.  Did he
discuss whether drone brood in SMR bees also suppressed mites?

>anti-varroa powers, but not a lot.  However, please note that there are no
>claims made for hygienic  behaviour in Harbo's stock, and there are no
>claims made about other desirable traits either.  His SMR bees simply do
not
>support varroa reproduction.  Period.


Some of the bees he used showed multiple resistance traits.  I will attach
two abstracts at the end of this email.

>incorporate this trait into their lines.  It is also possible that breeders
>will simply identify this trait in their existing lines and select for
it --
>assuming that it is not strongly linked to some unacceptable
characteristic.


Let's do it!

Gavin.


Title: Honey bees (Hymenoptera: Apidae) in the United States that express
resistance to Varroa jacobsoni (Mesostigmata: Varroidae).
Author: Harbo, John R., Hoopingarner, Roger A.
Author Address: [a] Honey Bee Breed. Genet. Physiol. Lab., USDA-ARS, Baton
Rouge, LA 70820, USA
Source: Journal of Economic Entomology 90 (4) 1997. 893-898.
Document Type: Research Article
Abstract: The purposes of this study were to select honey bees, Apis
mellifera L., for resistance to varroa mites, Varroa jacobsoni Oudemans, and
to find a probable cause for this resistance. As a genetic source, we
assembled 8 colonies that we thought had potential for resistance to varroa.
Queens and drones were propagated from this group to produce 43
instrumentally inseminated queens, each queen mated to only 1 drone.
Colonies from 27 of these queens were tested in Louisiana and 16 were tested
in Michigan. Each colony in the Louisiana test began with 986 +- 13 g (mean
+- SD) of bees and apprxeq 290 mites; Michigan colonies began with 3,212 +-
171 bees and apprxeq 51 mites. The populations of mites and bees were
measured 10 wk later. Three of the 43 colonies had fewer mites at the end of
the test than at the beginning. During the experiment, we evaluated each
colony for grooming behavior, hygienic behavior, the duration of the
postcapping period, and the frequency of nonreproducing mites in brood
cells. Of these 4 characteristics, only nonreproduction of mites was highly
related to a change in the mite population. The duration of the postcapping
period was marginally related, and the other 2 characteristics were
apparently unrelated to the growth of the mite population. This study showed
that resistance to varroa mites is present in the honey bee population in
the United States, nonreproduction of mites was highly correlated with the
growth of a mite population, and nonreproduction of mites may be a valuable
characteristic for selecting bees for resistance to varroa mites.

Title: Heritability in honey bees (Hymenoptera: Apidae) of characteristics
associated with resistance to Varroa jacobsoni (Mesostigmata: Varroidae).
Author: Harbo, John R. [a] Harris, Jeffrey W.
Author Address: [a] Honey Bee Breeding, Genetics and Physiology Laboratory,
USDA-ARS, Baton Rouge, LA, 70820, USA
Source: Journal of Economic Entomology 92 (2) April, 1999. 261-265.
Document: Type Article
Abstract: This study uses sibling analysis to measure the heritability in
honey bees, Apis mellifera L., of characteristics that have been associated
with resistance to the mite, Varroa jacobsoni Oudemans. Twenty-eight uniform
colonies of bees were established on 13 May in Baton Rouge, LA, each with 1
kg of mite-infested bees and a queen. The 28 unrelated queens in these
colonies were divided into 7 groups of 4 based on the insemination of 4
queens with the same mixture of semen from 1 of 7 sire colonies. After
worker progeny from these queens had replaced the initial bee populations, a
colony was related as a full sister to the other 3 colonies in its sire
group and unrelated to the other 24 colonies. Heritability (h2) was 1.24 for
proportion of mites in brood, 0.65 for hygienic behavior, 0.89 for the
duration of the capped period, 0.46 for suppression of mite reproduction,
and 0.00 for physical damage to mites (measured by the presence of
physically broken or dented mites on the bottom board). These results
suggest that it should be possible to enhance the expression of 4 of these 5
characteristics with selective breeding of bees, thus reinforcing confidence
in our ability to breed honey bees for resistance to V. jacobsoni.