Quantitative trait locus (QTL) main effects and QTL by environment (QT
LxE) interactions for seven agronomic traits (grain yield, days to hea
ding, days to maturity, plant height, lodging severity, kernel weight,
and test weight) were investigated in a two-row barley (Hordeum vulga
re L.) cross, Harrington/TR306. A 127-point base map was constructed f
rom markers (mostly RFLP) scored in 146 random double-haploid (DH) lin
es from the Harrington/TR306 cross. Field experiments involving the tw
o parents and 145 random DH lines were grown in 1992 and/or 1993 at 17
locations in North America. Analysis of QTL was based on simple and c
omposite interval mapping. Primary QTL were declared at positions wher
e both methods gave evidence for QTL. The number of primary QTL ranged
from three to six per trait, collectively explaining 34 to 52% of the
genetic variance. None of these primary QTL showed major effects, but
many showed effects that were consistent across environments. The add
ition of secondary QTL gave models that explained 39 to 80% of the gen
etic variance. The QTL were dispersed throughout the barley genome and
some were detected in regions where QTL have been found in previous s
tudies. Eight chromosome regions contained pleiotropic loci and/or lin
ked clusters of loci that affected multiple traits. One region on chro
mosome 7 affected all traits except days to heading. This study was an
intensive effort to evaluate QTL in a narrow-base population grown in
a large set of environments. The results reveal the types and distrib
utions of QTL effects manipulated by plant breeders and provide opport
unities for future testing of marker-assisted selection.