Table 2. Percentage of Bt-susceptible alleles from two T. ni backcrosses with no chromosomal crossing over.

	Individuals genotyped	% progeny that inherit a chromosome from the susceptible strain
		RpL8	Cadherin	APN5	ALP
Chromosomea		15	6	9	3
Cry1Ac bioassay	57	0.0	38.6	47.4	64.9
Untreated control	65	50.8	43.1	43.1	46.2
χ-Squared		39.67	0.25	0.23	4.31
P-value		<<0.0001	0.62	0.63	0.037

T. ni crosses were performed using Bt-resistant strain GLEN-Cry1Ac-BCS (Wang et al. 2007) and a Bt-susceptible strain purchased from Benzon Research (Carlisle, PA). F₁ females inherited one chromosome set from the susceptible grandmother and one chromosome set from the resistant grandfather. As there is no crossing over in females, backcross progeny inherit one complete maternal chromosome derived from a susceptible or resistant origin. Data set combines two related families: cross A (31 bioassay survivors, 35 untreated controls) and cross B (35 bioassay survivors, 30 untreated controls). Bioassay survivors did not inherit any RpL8 alleles derived from the susceptible grandmother, indicating that this gene is on the same chromosome as the Bt resistance locus. The ALP allele from the Bt-susceptible strain shows a significant overrepresentation in bioassay survivors; however, this is probably due to small sample sizes.

^aIndicates the B. mori chromosome containing this gene ortholog.