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.