PREHARVEST SPROUTING TOLERANCE IN 3 TRITICALE BIOTYPES

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.