Biology Reference
In-Depth Information
females during mass rearing. Most genetic-sexing strains are based on maintain-
ing marker genes (such as
white pupa
or a temperature-sensitive lethal) within
chromosomal translocations. However, because translocations can undergo
recombination in the region between the translocation breakpoint and the
marker gene, the strains are not completely stable. As a result, if no practical
means exist to remove the recombinants, an increasing number of “undesir-
able” females will be reared and released.
Ideally, a genetic-sexing method would produce ONLY males of high quality and
vigor to compete with wild males for female mates. Because an all-male colony will
be difficult to maintain (!), this character ideally would be a conditional trait, per-
haps dependent upon temperature or some other environmental cue. Developing
genetic-sexing systems based on transgenic methods could result in more-stable
lines than those based on translocations. Likewise, developing transgenic methods
to cause male sterility also could be beneficial for a sterile-insect release method
(SIRM) program. Sterilizing males by irradiation makes them less it because it
causes general somatic damage. Eliminating this fitness loss could allow fewer
males to be released, also resulting in a significant savings in program costs.
Recent studies on dipteran pests, such as
Lucilia cuprina
(
Concha and Scott 2009
),
the Mediterranean fruit fly (
Pane et al. 2005, Saccone et al. 2011
),
Anastrepha
fruit
flies (
Ruiz et al. 2007, Sarno et al. 2010
), and
Bactrocera dorsalis
and
B. correcta
(
Permpoon et al. 2011
), indicate that
doublesex
+
,
transformer
+
and
transformer-2
+
are homologs of the
Drosophila
genes and function in a similar manner. In fact,
Schetelig et al. (2012)
were able to induce male-only progeny in
Anastrepha sus-
pensa
using RNA interference (RNAi) by injecting double-stranded (ds) RNA for
transformer
+
and
transformer-2
+
into embryos. Nearly all the XX embryos, which
should have been female, developed into fully masculinized males with no appar-
ent female morphology and with gonads that were hypertrophied. They concluded
that both
transformer
+
and
transformer-2
+
genes are essential to development of
Anastrepha
females and that this technology could result in male-only populations
for genetic-control programs.
Sex determination in
Bombyx mori
, in which females are ZW and males are WW,
has been studied (
Ohbayashi et al. 2001, Suzuki et al. 2001, Nagaraja et al. 2005,
Shukla et al. 2011
). The knowledge obtained holds promise of developing genetic-
sexing strains in pest Lepidoptera for genetic-control programs (
Marec et al. 2005
).
10.14.2 Genetic Improvement of Parasitoids
Genetic improvement of parasitoids reared for augmentative biological control
could be achieved if the proportion of females produced in the rearing program
