Cultivar and age differences in the production of allelochemicals by Secale cereale

Concentrations of DIBOA [2,4-dihydroxy-1,4-(2H)-benzoxazine-3-one] and BOA [2-(3H)-benzoxazolinone], described previously as major allelochemicals in Secale cereale (rye), were determined in eight field-grown cultivars, harve sted at booting, using high-performance liquid chromatography (HPLC). Allel ochemicals were also quantified in greenhouse-grown cultivar 'Bates' harves ted 30, 45, 60, and 75 days after planting (DAP). The total production of D IBOA and BOA from field-grown S, cereale ranged from 137 to 1,469 mu g g(-1 ) dry tissue among the eight cultivars. 'Bonel' cultivar had the highest hy droxamic acid (HA) content and 'Pastar' the lowest. Bonel also showed the h ighest activity on Eleusine indica (goosegrass) and Pastar the least, in cu lture plate bioassays using aqueous extracts. HA content in shoot tissue va ried with S. cereale maturity. The greatest level of Hh in greenhouse-grown Bates was obtained 60 DAP compared to 30 DAP.