The F2 screen is a powerful method for finding and determining the
frequency of rare recessive alleles in a population. The most efficient method
of performing the screen is by starting with mated field-collected females. However,
F2 screens can also be performed starting with field collected males.
These male screens would be performed in the same way as the female screens, with
the difference being the need to supply virgin females from a known susceptible
colony to the males. The shortcoming is that only two genomic haplotypes are screened
rather than the four carried by mated females. Benefits include males may be easier
to collect than females, and by using multiple mates per male, there is a higher
probability of having a sufficient F1 population to complete an accurate
screen. The results from male screens can be combined with data derived from mated
female screens. We have performed both types of F2
screens during the years 2000 through 2003 on Ostrinia nubilalis (Hübner)
populations from Kansas and Texas. We have screened 95 female and 12 male lines
from this area during the years 2000 to 2002. The preliminary results indicate
that the frequency of resistance is <7.24 x 10-3 with 95% confidence
in the southern United States corn belt.
Species 1: Lepidoptera Crambidae Ostrinia nubilalis (European corn borer)
Keywords: Bt resistance, allele frequency
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