Preharvest sprouting is a major constraint to the utilization of triti
cale for human consumption in regions where moist, humid conditions pr
evail during harvest. To examine variation for different components of
preharvest sprouting tolerance (PST), trials were conducted over six
environments in Mexico. Seed dormancy, bract related chemical and mech
anical inhibitory effects and falling number. (FN) were measured in pr
imary and secondary triticales and their wheat and rye progenitors. Se
ed dormancy contributed 78% to PST with significant variation among an
d within triticale biotypes and progenitor species for bract water sol
uble inhibitors, bract mechanical barriers and FN. Bract chemical inhi
bition was higher when soil moisture was non-limiting in moisture-stre
ss/non-stress experiments, suggesting the presence of inhibitors other
than abscisic acid. In combination, tolerance components enhanced PST
. Substituted triticales [2D(2R)] showed higher seed dormancy and brac
t related tolerances compared with other triticale biotypes and displa
yed PST equivalent to wheat. The higher PST in wheat could be attribut
ed to higher FN levels. Components of PST evident in the wheat and rye
progenitors were suppressed by wheat/rye genomic interactions in prim
ary triticales. The selection of triticales with high stable FN will b
e an important first step in the development of PST cultivars, by prov
iding the building block upon which seed dormancy and other related fa
ctors can be introduced.