Insect resistance in soybean, Glycine mnu (L.) Merr., is inherited quantita
tively and has been difficult to incorporate into high-yielding cultivars.
The objectives of this study were to: (i) use restriction fragment length p
olymorphism (RFLP) markers to identify quantitative trait loci (QTLs) for a
ntixenosis (nonpreference) resistance to corn earworm, Helicoverpa tea Bodd
ie, in soybean plant introductions PI171451 and PI227687, (ii) determine th
e location of the QTLs on the public soybean genetic linkage map, (iii) det
ermine their relative magnitude and gene action, and (iv) compare them to i
nsect resistance QTLs previously detected in PI229358. RFLP maps were const
ructed in two insect-susceptible x insect resistant soybean populations: Co
bb x PI171451 and Cobb x PI227687. Insect resistance was measured either in
the field or greenhouse as percentage defoliation by corn earworm on veget
ative soybean plants. Marker-QTL associations were detected by interval map
ping and confirmed by single-factor analysis of variance. Comparisons were
made between QTLs identified in this study and those identified previously
using PI229358 as the source of insect-resistant germplasm. Among the three
resistant genotypes (PI171451, PI227687, and PI229358) a QTL on linkage gr
oup (LG) 'H' was shared among all three genotypes (accounting for an R-2 Of
19, 9, and 17%, respectively), and a major QTL on LG 'M' was shared betwee
n PI171451 and PI229358 (R-2 = 37% for each). A minor QTL on LG 'C2' was id
entified which was unique to PI227687 (R-2 = 11%) and a minor QTL on LG 'D1
' was identified which was unique to PI229358 (R-2 = 12%) In addition, a QT
L was found on LG 'F' in the susceptible genotype, Cobb (R-2 = 20%). This Q
TL is in a region of the soybean genome which has been previously associate
d with a cluster of soybean pathogen-resistance loci.