Agriculture Reference
In-Depth Information
artificial insemination, few bee breeders have undertaken an entire hybrid-breeding
programme.
Selecting traits
Hygienic behaviour is probably one of the bee breeder's most successful achievements.
This trait benefits colonies in terms of disease resistance: hygienic bees will remove
infected larvae within 24 hours of their appearance and so quickly prevent the build-up
of harmful organisms. After a few generations of bees bred from colonies that express
this trait, hygiene can become a fixed trait in a population of bees.
But how do you check for the existence of such a trait? In this case, the procedure was
fairly simple. Blocks of around 100 capped brood were frozen, and each colony was
timed to see how long it took the worker bees to clear away the dead brood. Those that
accomplished this task the most quickly (i.e. in under 24 hours) were used to propagate
from.
Other traits that have been successfully encouraged include, in the USA where they are
a problem, a resistance to tracheal mites and, more recently, the SMR trait in the fight
against the varroa mite discussed in Chapter 10. Other experiments in breeding and
crossing bee lines have gone spectacularly wrong, such as the efforts associated with
the extremely aggressive Africanized bees that are now causing such a problem as they
advance into the USA.
The selection of high brood viability (i.e. a loss of sex alleles in the population, leading
to inbreeding depression) can also be achieved by beekeepers fairly simply through
programmes such as the one described below. If you cut out a parallelogram measuring
5.3 cm (2⁄
in) by 5.3 cm from a piece of card, you should find that there are 100 cells
in this cut-out if you place it over a frame of brood. Position it over the most solidly
sealed area of brood and count the number of empty cells. Subtract this number from
100. The result should give a percentage brood viability, and anything above 85% is
acceptable. Once this trait - or any other trait - is elected, it can be propagated, as the
example below shows.